Annual Report Department of Highways 2025

Inter-city Motorway No. 6 (M6), Lam Takhong Dam, Sikhio District, Nakhon Ratchasima ProvinceAnnual Report 2025 Department of Highways 49

HighwayDevelopment Planning Highway Development Planning is a core mission of the Department of Highways, encompassing: 1) defining and analyzing strategies and goals for highway network and inter-city motorway development; 2) conducting short-, medium-, and long-term highway development studies and planning to guide project selection and prioritization; and 3) assessing the engineering and economic feasibility, as well as environmental impacts, of projects. In the fiscal year 2025, the Department of Highways undertook the following key highway development planning activities:1. The development of a new highway network connecting double-track railway stations on the Den Chai - Chiang Rai - Chiang Khong line The State Railway of Thailand (SRT) is constructing the new double-track railway project on the Den Chai - Chiang Rai - Chiang Khong line, with a total length of approximately 323 kilometers, encompassing Phrae, Lampang, Phayao, and Chiang Rai provinces. The project is expected to enhance national competitiveness and reduce travel and freight costs, with commercial operations scheduled to commence in 2028. Additionally, the project will support the development of a multimodal transport hub in Chiang Khong District through a public-private investment initiative. The new railway alignment intersects with several highways thereby influencing traffic conditions within the highway network; it will also stimulateurban development along the railway corridor.As the Department of Highways recognizes that vehicular traffic may be impacted within the highway network,it has established integrated highway development plans with other modes of transport. This initiative’s objective is to support efficient connectivity between highways and railway stations, as well as container yards. Upon completion, the project will significantly enhance the standard of integrated connectivity between road and rail transport systems, providing greater convenience, and efficiency, for road users.Alignment of the New Double-track Railway Project:Den Chai - Chiang Rai - Chiang KhongSource: The New Double-track Railway Project on the Den Chai -Chiang Rai - Chiang Khong Line50 Annual Report 2025 Department of Highways

2. Feasibility study and planning for the Inter-city Motorway No. 82 (Bang Khun Thian - Pak Tho), Ban Phaeo - Pak Tho SectionInter-city Motorway No. 82 (Bang Khun Thian - Pak Tho) is a key component of the Department of Highways’ road networks. The original project concept specified an elevated roadway with special standards constructed along the median of Highway No. 35 (Rama II Road), with the Wang Manao Interchange serving as a major gateway to the southern provinces. The motorway starts at the interchange with Inter-city Motorway No. 9 (the Bangkok 2nd Outer Ring Road) and terminates at the Wang Manao Interchange on Highway No. 4 (Phet Kasem Road), spanning approximately 75 kilometers. As of 2025, the Department of Highways had completed construction of Inter-city Motorway No. 82 for the Bang Khun Thian - Ekkachai Section, while the Ekkachai - Ban Phaeo Section is currently under construction and completion is expected in 2026. However, changes in economic conditions and travel behavior along Highway No. 35, particularly in the Ban Phaeo - Pak Tho Section, juxtaposed by ongoing new road, rail, and expressway network developments, may affect traffic volumes and call into question the suitability of the project design in comparison with the original study.In this context, the Department of Highways considers it necessary to conduct an analysis and develop a plan for the Inter-city Motorway No. 82 (Bang Khun Thian - Pak Tho), Ban Phaeo - Pak Tho Section. The study area covers Bangkok, Samut Sakhon, Samut Songkhram, and Ratchaburi provinces, including adjacent and affected areas, as shown in the project location map.3. Study and preparation of a Ten-year IntegratedHighway Development Plan for Transportation (2028-2037) The Department of Highways is responsible for managing and developing the national highway network, which is a critical component of the transportation infrastructure system and a key driver of national development. Highway development aims to support integrated multimodal transport utilization to enhance the country’s transport efficiency, elevate competitiveness in the transportation sector, and promote production base expansion and economic growth along transportation corridors. This will contribute to sustainable urban and peri-urban area development and accommodate future economic growth. Moreover, highway network development is an important driver for positioning Thailand as a transportation hub in Southeast Asia.Accordingly, the Department of Highways must prepare a new road transportation network development plan that aligns with directions for national infrastructure and logistics development that emphasizes rail transport systems and seamless multimodal connectivity. Nevertheless, road transportation remains essential for linking other modes of transport and serving as a backup network when other transportation systems are disrupted. This study aims to develop both 5-year and a 10-year highway development plans to provide a framework for determining appropriate and sustainable directions for highway development consistent with national development strategies, traffic conditions, and the country’s evolving economic and social contexts.Ten-year Integrated Highway Development Plan for Transportation (2028-2037)Annual Report 2025 Department of Highways 51

4. Feasibility study and preparation of a highway network development master plan to support international trade gateway connectivityThe Department of Highways is responsible for managing and developing Thailand’s ASEAN Highway network. Its mandate is to develop the road transportation network as a means to support cross-border freight transport between Thailand and neighboring countries in an efficient, convenient, rapid, and safe manner, under the framework of economic cooperation in key sub-regional initiatives. It is therefore necessary to conduct a feasibility study and develop a master plan for highway network development to support international trade gateway connectivity over the next 20 years. This will enhance the efficiency of the existing highway network and ensure its capacity to continuously and seamlessly accommodate increasing volumes of freight transport through international checkpoints between Thailand and neighboring countries. The objectives of this study are to establish criteria and guidelines for selecting potential project border areas suitable for highway network development to support international trade gateway connectivity; analyze the traffic conditions and topographical characteristics of each project area; and conduct preliminary economic, engineering, and environmental feasibility studies. The findings will facilitate improvements in highway network efficiency and the formulation of development plans for selected project areas to strengthen international trade gateway connectivity in the short, medium, and long terms.Study areas of provinces bordering neighboring countriesSource: Highway Network Development Master Plan to Support International Trade Gateway Connectivity5. Study and preparation of an integrated plan for traffic development and problem mitigation in Bangkok and its environsBangkok currently continues to face persistent traffic congestion problems that impact the daily lives of the public in multiple dimensions. These include but are not restricted to public health and safety, property security, the generation of economic losses, budgetary burdens, and reduced overall investment efficiency. These long-standingproblems are attributable to various factors, such as dense land use in economic zones, labor mobility issues, the rapid growth in vehicle numbers that outpace road network development, ineffective traffic management, flooding on roads, and urban sprawl. As a result, traffic congestion has permeated from Bangkok to surrounding provinces.Over time, the Department of Highways has managed approximately 1,500 kilometers of national highways in Bangkok and its environs. This network is essential for connecting commuter and freight transport with other travel modes, including rail, water, and air transport systems managed by other agencies. Therefore, addressing traffic congestion on the national highway network in Bangkok and its environs requires a systematic, integrated approach in collaboration with relevant agencies to resolve existing issues and accommodate future traffic growth. The associated study has two implementation phases:(1) Short-term phase - focuses on improving traffic efficiency and reducing travel delays through upgrades to physical infrastructure in problem areas, such as road widening; installation or improvement of traffic signal systems, signage, roundabouts, and medians; improvements to drainage systems and structures; and traffic management measures.(2) Long-term phase - focuses on developing large-scale infrastructure in line with highway development plans, such as adding traffic lanes, constructing bridges and interchanges, improving U-turn locations, and upgrading highway standards to effectively accommodate future traffic demand.52 Annual Report 2025 Department of Highways

NetworksStatus: As of September 2025Note: (*) Includes three projects approved by the Cabinet on 18 October 2016 to utilize foreign loans (50% financing share).(**) Some projects may utilize foreign loans for implementation.6. Four-lane expansion of primary highways (Phase 2)Following the completion of the Four-Lane Expansion of Primary Highways (Phase 1) in 1996, the Cabinet authorized the Ministry of Transport, through the Department of Highways, to implement a plan for expanding primary highways into four traffic lanes (Phase 2). This plan encompasses the upgrade of primary highway routes across all regions, covering 11 networks with a total distance of 5,246.21 kilometers. Project progress is summarized below:Network 1: Nakhon Sawan - Phitsanulok - Den ChaiDistrict - Phrae - Ngao District (including Phrae - Nan)Network 2: Mae Sot District - Tak - Sukhothai -Phitsanulok - Lom Sak District - Chum Phae District -Khon Kaen - Kalasin - MukdahanNetwork 3: Saraburi - Phetchabun - Lom Sak District - LoeiNetwork 4: Ban Hin Kong - Nakhon Nayok - Prachin Buri -Aranyaprathet District - Thai/Cambodian BorderNetwork 5: Nakhon Pathom - Suphan Buri - Pa Mok District - Saraburi (including Kanchanaburi - Suphan Buri)Network 6: Nakhon Sawan - Chaiyaphum - Ban Phai District - Maha Sarakham - Roi Et - Yasothon - Ubon Ratchathani - Chong MekNetwork 7: Sattahip District - Phanom Sarakham District -Kabin Buri District - Pak Thong Chai District -Chok Chai District - Nang Rong District - Prasat District -Ubon Ratchathani - Mukdahan (including Sikhio District -Chok Chai District)Network 8: Surat Thani - Nakhon Si Thammarat -Songkhla - Hat Yai District (including Songkhla - Chana District)Network 9: Phuket - Phang-nga - Krabi - Trang - Phatthalung (including Huai Yot District - Nakhon Si Thammarat)Network 10: Loei - Udon Thani - Sakon Nakhon - Nakhon PhanomNetwork 11: Other networks including Sak Lek District -Wang Thong District, Sukhothai - Sawankhalok, Sikhio District - Chaiyaphum, Kaeng Khro District - Chum Phae District, Chumphon - Ranong, and Surat Thani - Phang-ngaTotalPercentage543.61752.36280.21196.00229.24507.67917.36343.16386.74304.96405.384,879.6393.00720.00-20.25--45.73---12.95-85.981.639-80.7391.58--90.28----18.02280.905.354563.61833.09392.04196.00229.24643.67917.36343.16386.74317.91423.405,246.21100.00Construction completed Total Ongoingconstruction (*)Under budgeting process (**)Unit: KilometersAnnual Report 2025 Department of Highways 53

7. Highway development to promote Special Economic Zones (SEZs)In 2015, the government introduced a policy to develop Special Economic Zones in 10 provinces as an initial phase. This initiative aimed to establish production hubs connected to the ASEAN region and foster the development of border towns, creating new economic zones that facilitate trade and investment with neighboring countries. The primary objectives were to promote regional prosperity, reduce social and income disparities, improve the quality of life for people in border areas, and strengthen border security.To support the development of these Special Economic Zones, the Department of Highways devised a comprehensive road infrastructure development plan spanning from 2014 to 2028. The plan includes 53 projects covering a total distance of 1,073.200 kilometers. As of 2025, 46 projects (967.091 kilometers) were completed, 3 projects (46.530 kilometers) were under construction, and 4 projects (59.575 kilometers) were planned for the future.8. Highway development to promote the Eastern Economic Corridor (EEC)The EEC is designed to promote investment and strengthen Thailand’s industrial sector. The scheme focuses on three key provinces: Chon Buri, Rayong, and Chachoengsao. To hone the development of the EEC, the Department of Highways has planned and executed a range of road infrastructure projects. Between 2014 and 2026, a total of 60 projects received funding. As of 2025, 49 projects had been completed, 11 projects were under construction, and five additional projects were allocated additional funding for the fiscal year 2027 to ensure the comprehensive development of the transportation network in the EEC area.9. Annual budget planningEach year, the Department of Highways develops and submits a budget proposal to the Budget Bureau for review and approval. This budget planning aligns with the national transportation development strategy and addresses urgent needs to alleviate societal strain. For the fiscal year 2025, the Department of Highways received the following budget allocations, categorized by project type:9.1 Large-scale construction projectsThe Department of Highways’ budget allocation includes funding for 83 new large-scale construction projects under the integrated transportation and logistics system development plan.Thailand’s Economic Corridor SchemeSource: Spatial Development Planning and Strategy Office, NESDC (January 2023)Following resolutions in 2022, the Special Economic Zone Development Policy Committee approved the designation of economic corridor areas across four regions. In response, the Department of Highways has outlined plans to develop road infrastructure to support and facilitate future growth in these corridors. The 73 planned projects number:1) 20 projects for the Northern Economic Corridor(NEC)2) 20 projects for the Northeastern Economic Corridor (NeEC)3) 17 projects for the Central-West Economic Corridor (CWEC)4) 16 projects for Southern Economic Corridor(SEC)54 Annual Report 2025 Department of Highways

Highway construction for transport and logisticsNational highway constructionBridge and interchange constructionManagement of highway hierarchy to enhance roadefficiency and safetyEnhancement of service efficiency on majorhighwaysAcceleration of the four-lane expansion of primary highways (Phase 2)Highway construction to support SEZ developmentConstruction of bridges at railway crossingsSolutions to traffic congestion in Bangkok, its surrounding areas, and major citiesConstruction of inter-city motorwaysHighway infrastructure development to support EEC developmentTotal1551127111112837.885605.115-21.040113.67019.73011.000-7.20022.8007.455815.895630.00039,545.0009,560.0003,320.0007,890.0001,100.000650.000350.000440.0009,800.0002,620.00075,905.00094.5006,364.2501,434.000521.0001,205.000165.00097.50070.00088.0001,470.000393.00011,902.250ActivitiesNumberof projects Distance(kilometers)Construction cost(million baht)Budget requestedfor fiscal year 2026(million baht)9.2 Small-scale construction projectsThe Department of Highways also implements small-scale highway construction and improvement projects that can be completed within one year with relatively modest budgets. These projects address specific issues and local needs, such as traffic congestion in community areas across the country. The goal is to maintain highways at proper standards while providing convenient, fast, and safe services to road users in supportof the highway construction project for area-based development. The following activities were carried out.9.2.1 Community highway development This program focuses on improving highways passing through residential communities to enhance traffic flow and safety. The improvements aimed to reduce accidents, minimize dust pollution, and promote economic and social development, ultimately enhancing quality of life for local residents.Before improvementAfter improvementAnnual Report 2025 Department of Highways 55

Before improvementAfter improvementAfter improvement9.2.2 Bridge and drainage system developmentThis initiative compresses the construction and improvement of small bridges and drainage structures to meet highway standards. Activities include building permanent drainagechannels, preventing bridge abutment erosion, and implementing other measures to enhance drainage efficiency and prevent flooding.9.2.3 Road shoulder construction While recent road construction projects have prioritized improving highway efficiency and upgrading standards to accommodate high traffic volumes, which is both necessary and appropriate, some important roads remain underdeveloped. A particular focus is needed on roads that lack proper shoulders. These roads, despite their significance for local communities, have not received necessary improvements or development attention. The shorter construction program aims to address this infrastructure gap.9.2.4 Highway efficiency improvement While large-scale construction projects require substantial budgets and lengthy approval processes, and are primarily aimed at resolving issues along entire travel corridors, such projects are often unable to promptly address urgent problems in specific areas that require immediate action each year. Small-scale highway improvements are implemented to efficiently address urgent issues on primary and secondary highway networks. These targeted interventions provide cost-effective, immediate benefits to the public while laying groundwork for future large-scale projects. Examples include Before improvementhighway improvements to promote economic activities, trade, and tourism; mitigation of bottleneck sections; enhancement of intersection efficiency to improve traffic flow; and the addition of passing lanes and climbing lanes for heavy trucks. In recent years, such problems have become more prevalent for several reasons, including community expansion and land development along highways, increased traffic volumes in terms of general travel, and the transportation of goods both within communities and across provinces, regions, and nationwide.56 Annual Report 2025 Department of Highways

Before improvementAfter improvement10.1 Performance evaluation using the analysis of levels of operational success in budget implementation using the Performance Assessment Rating Tool (PART) This evaluation was conducted for the Department of Highways’ three core mandates: highway construction, highway rehabilitation, and traffic safety management. The assessment was based on clearly defined goals and target indicators in terms of outputs, outcomes, efficiency, and effectiveness across quantitative, qualitative, time, and cost dimensions. The assessment results indicated that budget expenditures for highway development projectshad achieved the established targets and demonstrated effectiveness.10.2 Evaluation of the Department of Highways Projects to foster EEC developmentThe highway development projects that foster EEC development aim to improve highway standards in Chon Buri, Rayong, and Chachoengsao provinces to accommodategrowing traffic volumes, reduce traffic accidents and congestion, and enhance comprehensive network connectivity. The evaluation scope covered the period from 2018 to 2024 and was conducted under evaluation criteria of the Organisation for Economic Co-operation and Development (OECD). The results indicated that a total of 59 projects with a combined investment value of 43,566.44 million baht were aligned with the National Strategy. The projects demonstrated economic efficiency (expenditures 5.26% below budget), high efficiency (on-schedule construction), and value for money. Direct benefits amounted to 55,437.26 million baht per year, derived from reduced vehicle operating costs, value of travel time, and reduced accident costs, with indirect benefits from increased land values totalling 160.27 million baht.For fiscal year 2025, the operation details are as follows:8522222043332,517.800461.900639.0006,739.30010,358.000ActivitiesWork PlanNumber Million Baht1. Community highwaydevelopment2. Bridge and drainage systemdevelopment3. Road shoulder construction4. Highway efficiencyimprovementTotal10. Project evaluationProject evaluation is the systematic collection and analysis of data to compare performance against established criteria or standards in order and assess the achievement of project objectives. The results are used to support project implementation and decision-making for planning and defining future projects. For the fiscal year 2025, the Evaluation Section under the Department of Highways’ Bureau of Planning conducted evaluations and analyzed the performance outcomes of projects and activities described hereunder.Annual Report 2025 Department of Highways 57

10.3 Highway development evaluation10.3.1 Evaluation of medium- and small-sized rest areas Rest areas are an essential component of road transport infrastructure, providing convenience and enhancing safety for road users. They help reduce accidents caused by driver fatigue and prevent accidents resulting from parking on road shoulders. Between 2021 and 2024, the Department of Highways constructed 94 medium-sized and 33 small-sized rest areas. The evaluation results indicated that these projects reduced accident-related losses by more than 72 million baht per year and generated fuel cost savings for freight vehicles of over 35 million baht per year. Concurrently, the effectiveness evaluation showed that the rest area projects had achieved their objectives and clearly met the needs of service users.10.3.2 Evaluation of the maximum speed limit measure of 120 km/h on national highways This evaluation was conducted on national highways in accordance with the Ministerial Regulation B.E. 2564 (2021). The measure was implemented on a pilot basis in four sections, using the Highway Accident Information Management System (HAIMS) accident data covering 13 years (2012-2024). Results showed that after enforcement of this measure, travel efficiency improved, with the average number of accidents decreasing from 469.33 to 402.50 cases per year. Accidents caused by driver error declined by 92.45%, and overall accidents on national highways fell by 87.67%. To further enhance safety, consideration should be given to closing U-turn points on median islands, constructing U-turn bridges or underpasses for large trucks, improving road surfaces and traffic signage, and building pedestrian overpasses.10.3.3 Evaluation of small underpasses connecting communities along highways Small underpasses are constructed to facilitate travel for small vehicles, motorcycles, and agricultural vehicles, reduce traffic conflicts between through-movement traffic and local traffic, and improve highway crossing safety. The Department of Highways has constructed 139 small underpasses nationwide, including overpass-type structures and box culverts. An evaluation was conducted on a sample of 51 underpass projects, comparing accident data within a 2-kilometer radius before and after construction. The results indicated that the construction of small underpasses had achieved its objectives and reduced accidents on national highways by 33.76%.10.3.4 Evaluation of motorcycle guardrails on horseshoe U-turn bridges The Department of Highways has established measures to improve and modify bridge guardrails at high-risk locations to prevent motorcycles from driving off bridges. This effectiveness evaluation of motorcycle guardrails installed on horseshoe U-turn bridges is used as additional information for policy regarding future road safety improvements. The Department of Highways is responsible for 121 horseshoe U-turn bridges (excluding those on inter-city motorways), of which 56 bridges have been upgraded with motorcycle guardrails. Among 45 bridges that had previously experienced accidents and were retrofitted with guardrails, only one bridge (located near Vongchavalitkul University in Nakhon Ratchasima Province) recorded a repeat accident involving a motorcycle fall, caused by riding against traffic onto the U-turn bridge. These findings confirm the effectiveness of the measure for reducing accidents and support the initiative to expand the installation of motorcycle guardrails on all U-turn bridges comprehensively.58 Annual Report 2025 Department of Highways

Highway Construction Highway No. 106 (Ban Muang Ton - Ban Bo Hin) extends for approximately 16.180 kilometers, covering the section from Sta. 119+820 to Sta. 136+000. Implemented under the Integrated Work Plan for Transport and Logistics System Development as the National Highway Network Construction Project, the highway features four lanes, built to Special Class Highway standards. The construction cost was 794,279,950 baht and the project was completed on 27 January 2025.Construction of Highway No. 4009 (Surat Thani - Ao Luek District), Ban Soi Sip - Ban Na San District SectionConstruction of Highway No. 201 (Ban Pha Nok Khao - Ban Lak Roi Hok Sip)Construction of Highway No. 1023 (Phrae - Wang Chin District), Ban Nam Rin - Wang Chin District SectionThe construction of Highway No. 201 (Ban Pha Nok Khao - Ban Lak Roi Hok Sip) was implemented under the Integrated Work Plan for Transport and Logistics System Development as the National Highway Network Construction Project. The highway extends for approximately 7 kilometers, covering multiple sections from Sta. 269+000 to Sta. 272+100 (new Sta.), Sta. 274+650 to Sta. 286+500 (new Sta.), and Sta. 289+400 to Sta. 295+005 (new Sta.), and features four lanes, built to Special Class Highway standards. The construction cost was 898,819,629 baht and the project was completed on 31 July 2025.The construction of Highway No. 4009 (Surat Thani -Ao Luek District), Ban Soi Sip - Ban Na San District Section, was implemented under the Integrated Work Plan for Transport and Logistics System Development as the National Highway Network Construction Project, The highway is approximately 23 kilometers in length, covering the section from Sta. 18+000 to Sta. 41+000, and features four lanes, built to Special Class Highway standards. The construction cost was 1,113,164,400 baht and the project was completed on 30 April 2025.The construction of Highway No. 1023 (Phrae - Wang Chin District), Ban Nam Rin - Wang Chin District Section, was implemented under the Integrated Work Plan for Transport and Logistics System Development as the National Highway Network Construction Project. The highway extends for approximately 43.5 kilometers, covering multiple sections from Sta. 23+000 to Sta. 33+500, Sta. 35+700 to Sta. 40+650, Sta. 43+000 to Sta. 53+447, Sta. 54+600 to Sta. 55+860, Sta. 57+425 to Sta. 59+500, Sta. 62+000 to 64+000, and Sta. 65+000 to Sta. 77+267. It is a two-lane highway, built to Class 1 Highway standards. The construction cost was 947,147,000 baht and the project was completed on 9 June 2025.Construction of Highway No. 106(Ban Muang Ton - Ban Bo Hin)Annual Report 2025 Department of Highways 59

Construction of Highway No. 304 (Chachoengsao - Khao Hin Son Subdistrict), Bang Khla District - Phanom Sarakham District Section, Section 3Construction of Highway No. 202 (Ban Nam Plik - Ban Nong Phue), Section 2The Bureau of Highway Construction 2 completed Highway No. 304 (Chachoengsao - Khao Hin Son Subdistrict), Bang Khla District - Phanom Sarakham District Section, Section 3 (Sta. 90+400 to Sta. 93+800), covering a total distance of 3.4 kilometers. The highway features six lanes, built to Special Class Highway standards, with the addition of a 3.5-meter-wide lane in each direction, separated by a depressed median. Portland cement concrete was used for the road surface. The highway also has two reinforced concrete bridges at Sta. 93+095 to Sta. 93+100, each spanning 38 meters; a reinforced concrete overpass crossing the Nong Pla Taphian Junction at Sta. 92+889 (505 meters in width); and roadway lighting and flashing beacon systems along the route.Highway No. 304 is a key logistics route under the Integrated Work Plan for the Eastern Economic Corridor (EEC), specifically the Highway Development for Supportingthe EEC Project, Highway Infrastructure Development to Support EEC Development activity. Therefore, upgrading this highway was necessary to accommodate heavy traffic volume. Project completion has improved transport efficiency by enhancing travel convenience, speed, and safety, while increasing capacity to support smoother and more orderly traffic flow and overall mobility.The Bureau of Highway Construction 2 completed Highway No. 202 (Ban Nam Plik - Ban Nong Phue), Section 2, covering the stretch from Sta. 339+500 to Sta. 367+100, with a total length of 27.6 kilometers. The highway features four lanes, built to Special Class Highway standards, with the addition of a 3.5-meter-wide lane in each direction. The inner shoulder is 2.24 meters wide in sections with a Type II single-slope concrete barrier median, and 0.5 meters wide where a raised median is provided. The outer shoulder is 2.5 meters wide, separated by a raised median. The highway has lighting and flashing beacon systems along the route. The project area is located within Pathum Ratchawongsa District in Amnat Charoen Province and Khemarat District in Ubon Ratchathani Province.Highway No. 202 forms part of a strategic plan to address traffic congestion and accidents, reduce transportation costs, and sustainably enhance national competitiveness. In line with Cabinet resolutions from a cabinet meeting of the Lower Northeastern Provincial Cluster, the project supports the strategy to improve travel mobility for road users in Yasothon and Amnat Charoen provinces. It also supports logistics development, accommodates growing traffic demand on major highway routes, alleviates urban congestion, alleviates accident issues, and enhances travel convenience and overall transport efficiency.60 Annual Report 2025 Department of Highways

Construction of an Interchange at the Intersection of Highway No. 37 and Rural Road No. Phor. Bor. 1010 (Chang Thaeng Krachat Intersection), Phetchaburi ProvinceConstruction of an Interchange at the Intersection of Highway No. 37 and Rural Road No. Phor. Bor. 1001 (Huai Tapaet Intersection), PhetchaburiProvinceThe Bureau of Bridge Construction completed an interchange at the intersection of Highway No. 37 and Rural No. Road Phor. Bor. 1010 (Chang Thaeng Krachat Intersection) in Phetchaburi Province. The project covered1.6 kilometers, spanning Highway No. 37 from Sta. 16+000 to Sta. 17+600 and 0.294 kilometers, spanning Rural Road No. Phor. Bor. 1010 from Sta. 7+936 to Sta. 8-230. The interchange includes a prestressed concrete I-girder bridge, U-turn points beneath the bridge (parallel to the main carriageway), entrance and exit ramps connecting to Rural Road No. Phor. Bor. 1010, and an at-grade intersection within the junction area (Rural Road No. Phor. Bor. 1010). There is a roundabout under the bridge connecting to and from Highway No. 37.The project also features reinforced concrete pavements, drainage systems and utility holes, effective lighting, road markings, and other related infrastructure.Following project completion, travel in the area has become more convenient, faster, and safer, while traffic volumes that are expected to increase in the future will be accommodated.The Bureau of Bridge Construction completed an interchange at the intersection of Highway No. 37 and Rural Road No. Phor. Bor. 1001 (Huai Tapaet Intersection) in Phetchaburi Province. The project covered Highway No. 37 from Sta. 9+700 to Sta. 11+200, for a total length of 1.5 kilometers, and Rural Road No. Phor. Bor. 1001 from Sta. 3+560 to Sta. 3+830, with a length of 0.27 kilometers. The interchange includes a prestressed concrete I-girder bridge, U-turn points beneath the bridge parallel to the main carriageway, entrance and exit ramps connecting to Rural Road No. Phor. Bor. 1001, and an at-grade intersection within the junction area (Rural Road No. Phor. Bor. 1001). There is a roundabout under the bridge connecting to and from Highway No. 37.The project also features reinforced concrete pavements, drainage systems and utility holes, effective lighting, road markings, and other related infrastructure.Following project completion, travel in the area has become more convenient, faster, and safer, while traffic volumes that are expected to increase in the future will be accommodated.Annual Report 2025 Department of Highways 61

International HighwayDevelopment The Fifth Thai-Lao Friendship Bridge (Bueng Kan - Bolikhamxay)The construction of the Fifth Thai-Lao Friendship Bridge (Bueng Kan - Bolikhamxay), together with highway network development, is a strategic initiative under the Greater Mekong Subregion (GMS) Economic Cooperation Framework and the Ayeyawady-Chao Phraya-Mekong Economic Cooperation Strategy (ACMECS). The project aims to connect Thailand with Lao PDR and neighboring ASEAN countries in order to promote trade, investment, and tourism. It enhances the competitiveness of the Northeastern region, facilitates more convenient, faster, and more efficient transportation of goods and travel, and contributes to improving the quality of life of local people.The associated road has a total length of 16.34 kilometers. It extends from Mueang Bueng Kan District in Bueng Kan Province, at Highway No. 222 (Sta. 123+430), crosses Rural Road No. Bor. Kor. 3217 and Rural Road No. Bor. Kor. 3013 and then passes through the Thai border checkpoint and Highway No. 212; it traverses the Fifth Thai-Lao Friendship Bridge (Bueng Kan -Bolikhamxay), continues through the traffic changeover point and the Lao PDR border checkpoint, and terminates at National Road No. 13 (R13) on the Lao PDR side.The road has four lanes, each lane being 3.50 meters wide with shoulders 2.50 meters wide, within a 60-meter right-of-way. The Fifth Thai-Lao Friendship Bridge is an extradosed prestressed concrete box girder structure; it has two lanes, shoulders, and sidewalks. The main span across the Mekong River is 810 meters long, with approach ramps on both sides; the total bridge length is 1,350 meters. Border control checkpoints are provided on both the Thai and Lao PDR flanks, and a traffic changeover point is located on the Lao PDR side.62 Annual Report 2025 Department of Highways

In terms of engineering design, the structure, which combines the key characteristics of a cable-stayed bridge and a prestressed concrete bridge, can support long spans of up to 150 meters between piers. This span length was determined based on the number and configuration of in-river structures to ensure adequate drainage capacity. The width of the central navigation span was also designed to be sufficient to accommodate the future passage of very large cargo vessels. Adoption of the extradosed prestressed concrete bridge results in a slender structural design, with the thickness of the mid-span segments being only 2.50 meters in diameter. Currently, this bridge style has become increasingly common in Thai construction projects. The Department of Highways deems the Fifth Thai-Lao Friendship Bridge (Bueng Kan - Bolikhamxay) to be the first international bridge to use this extradosed prestressed concrete bridge design.Additionally, this bridge is Thailand’s first international bridge to be equipped with a Bridge Health Monitoring System (BHMS) from the initial construction stage. The system conducts engineering-based monitoring, tracking, and surveillance of the bridge structure using advanced technologies and modern sensors installed at key locations along the structure. These sensors monitor the bridge’s behavior under actual service conditions, enabling early detection and prevention of potential structural damage. As a result, the Department of Highways can continuously inspect structural safety, develop accurate and effective maintenance plans, reduce maintenance costs, and sustainably extend the bridge structure’s service life.In terms of architecture, the bridge features a distinctive cultural identity. The design of the upper bridge pylons beautifully and uniquely incorporates representation of the “Khaen,” a traditional musical wind instrument that symbolizes the common cultural heritage of the Thai and Lao people who live along the Mekong River.Overall, the bridge reflects collaboration in engineering, technology, economics, the environment, and architecture that embodies the cultural identity shared between the two countries. It represents a significant milestone in connecting economies and communities for the sustainable mutual growth of Thailand and Lao PDR. The bridge was completed and opened to traffic in December 2025.Annual Report 2025 Department of Highways 63

High-speed RailThetsaban 2 RoadChon BuriStarting PointPattayaBangkokU-Tapao Toll PlazaRayongApprox.2 km longSta. 186+307SattahipEnd PointU-Tapao AirportSta. 192+000Eastern Economic Corridor Highway Network Development for Climate Change Adaptation: Inter-city Motorway No. 7 Extension Connecting to U-Tapao International AirportThe Inter-city Motorway No. 7 Extension Connecting to U-Tapao International Airport is a new elevated highway being developed as part of the Eastern Economic Corridor (EEC) highway network expansion. The project aims to improve transportation infrastructure that supports EEC growth, particularly the development of U-Tapao Airport as Thailand’s third major international aviation hub. The new elevated highway will connect the airport to the main transportation system, providing faster, safer, and more convenient access to the airport, thus promoting commercial aviation growth, and attracting investment in the EEC.Located in Ban Chang District, Rayong Province, the project includes the construction of a 1.92-kilometer, four-lane elevated highway with service roads at ground level. It also involves the expansion of a 5.65-kilometer section of Highway No. 3 (Sukhumvit Road) from Sta. 186+350 to Sta. 192+000 to improve access to U-Tapao Airport’s new passenger terminal. Approved by the Cabinet in 2022, the project is supported by the Asian Development Bank (ADB), which has played a key role in project planning and assessment. Reflecting ADB’s sustainable development policies, the project goes beyond construction to focus on improving the quality of life for local residents and supporting the Department of Highways. This thrust includes community education programs on road safety and social equality, development of the department’s road safety plans, provision of the project office and accommodation facilities based on environmentally friendly construction, and gender equality training for department personnel.64 Annual Report 2025 Department of Highways

The Department of Highways signed the construction contract on 1 August 2025 with Sino-Thai Engineering and Construction Public Company Limited undertaking project construction; a consortium of Epsilon Co., Ltd. and Index International Group Public Company Limited was engaged as the construction supervision consultant. The contractor commenced work on 6 October 2025, with a construction period of 1,080 days, and the construction is expected to be completed in early 2028.Annual Report 2025 Department of Highways 65

Inter-city Motorway No. 81 (M81), Bang Yai - KanchanaburiThe Inter-city Motorway No. 81 (Bang Yai - Kanchanaburi) (M81) is a key project under the Thailand’s Transport Infrastructure Development Plan and the 20-year Inter-city Motorway Development Master Plan. The development of M81 is expected to enhance transportation connectivity between Bangkok and its metropolitan area and the Kanchanaburi Special Economic Zone, while at the same time supporting the development of the Central-Western Economic Corridor (CWEC). It will promote growth in industry, agriculture, and tourism, serving as a critical mechanism for driving and sustaining Thailand’s economic development in the future.The M81 Inter-city Motorway will provide integrated connectivity with major highway and inter-city motorway networks. There will be direct connections to Inter-city Motorway No. 8 (M8) Nakhon Pathom - Pak Tho Section, the Bangkok 3rd Outer Ring Road (M91), Inter-city Motorway No. 9 (M9), the Western Bangkok Outer Ring Road (Bang Khun Thian - Bang Bua Thong - Bang Pa-In Section), and Phet Kasem Road (Highway No. 4). This integrated network will create seamless connectivity between the highway and intercity motorway networks linking the western and southern regions. Inter-city Motorways66 Annual Report 2025 Department of Highways

Project DetailsThe Inter-city Motorway No. 81 (Bang Yai -Kanchanaburi) is 96 kilometers in length and designed as a fully controlled-access motorway. The route begins at the interchange between Inter-city Motorway No. 9 (Western) and Rattanathibet Road at Bang Yai Interchange in Bang Yai District, Nonthaburi Province, and terminates at Highway No. 324 (Kanchanaburi Phanom Thuan District Road Section) in Tha Muang District, Kanchanaburi Province. The motorway has 4-6 traffic lanes and is equipped to support both Multi-Lane Free Flow (M-Flow) and Manual Toll Collection (MTC) systems. There are eight toll plazas along the route: Bang Yai, Nakhon Chai Si, Sisa Thong, Nakhon Pathom (East), Nakhon Pathom (West), Tha Maka, Tha Muang, and Kanchanaburi. To enhance user convenience and safety, there are rest areas along the corridor, i.e. the Nakhon Chai Si Service Area, Nakhon Pathom Service Area, and Tha Maka Rest Stop. Additionally, the Central Control Building (CCB), located at the Bang Yai Toll Plaza, houses the Traffic Operation Center, which serves as the core facility for integrated control and management of all subsystems to ensure efficient and coordinated operations. These subsystems include the traffic control surveillance system, vehicle weight control system, main server rooms for traffic management and toll collection systems, electrical and mechanical equipment rooms, and user information service center.Project ProgressThe Department of Highways has completed construction under 25 civil works contracts for the project. Regarding the public-private partnership (PPP) for system construction and operation and maintenance, the concession agreement was signed on 29 September 2021. Construction of toll plazas and system works was subsequently initiated and had reached 97% completion as of October 2025. On 31 October 2025, the Department of Highways officially commenced a trial operation, providing free service without toll collection along the entire 96-kilometer route, and full operations with toll collection are expected to begin in January 2026.Toll rates for Inter-city Motorway No. 81(Bang Yai - Kanchanaburi)Annual Report 2025 Department of Highways 67

Inter-city Motorway No. 82 (M82), Bang Khun Thian - Ban PhaeoProject BackgroundThe Department of Highways has implemented a strategic plan for Inter-city Motorway No. 82 (Bang Khun Thian - Pak Tho), with the initial phase covering the Bang Khun Thian - Ekkachai - Ban Phaeo Section to alleviate traffic congestion on Highway No. 35 (Rama II Road). The project is part of the Ministry of Transport’s Urgent Action Plan for Transportation and is aligned with the 20-Year Inter-city Motorway Development Master Plan (2017-2036) and the Ministry of Transport’s Strategic Plan (2017-2021) regarding infrastructure investment, regional and global connectivity enhancement, and the development of transport and logistics systems to accommodate increasing traffic volumes and facilitate travel to the southern region. Civil works for the Bang Khun Thian - Ekkachai Section (3 contracts) are funded by the government, while the Ekkachai - Ban Phaeo Section (10 contracts) is sourced from toll revenue funds under the supervision of the Motorway Fund Administrative Committee to reduce burden on the national economy.Inter-city Motorway No. 82 (Bang Khun Thian -Pak Tho), Bang Khun Thian - Ekkachai Section, directly connects to central Bangkok via the Rama III -Dao Khanong - Western Bangkok Outer Ring Road Expressway of the Expressway Authority of Thailand (EXAT). It will ease heavy congestion on Highway No. 35 (Rama II Road), which currently faces very high and further escalating traffic volumes. Furthermore, the Ekkachai to Ban Phaeo section provides a direct gateway from central Bangkok to the southern region of Thailand. It is a vital route that supports and accommodates development in accordance with national policies and strategies at all levels and in all dimensions. This project acts as a catalyst for economic, social, and tourism growth, and strengthens road transport security and logistics connectivity to southern Thailand.Project DetailsInter-city Motorway No. 82 (Bang Khun Thian -Ban Phaeo) is designed as an elevated roadway constructed along Highway No. 35 (Rama II Road). Built to motorway standards, it features full access control and supports a Multi-Lane Free Flow (M-Flow) system. The project is approximately 25 kilometers long with a 6-lane elevated roadway along Rama II Road directly connecting with the Rama III - Dao Khanong - Western Bangkok Outer Ring Road Expressway operated by EXAT. The project includes seven toll plazas along the route: Bang Khun Thian Toll Plaza, Phan Thai Norasing Toll Plaza, Maha Chai 1 Toll Plaza, Maha Chai 2 Toll Plaza, Samut Sakhon 1 Toll Plaza, Samut Sakhon 2 Toll Plaza, and Ban Phaeo Toll Plaza.Project ProgressInter-city Motorway No. 82 (Bang Khun Thian -Ban Phaeo), Bang Khun Thian - Ekkachai Section (3 contracts), has been successfully completed and has commenced trial operations. A trial service covering a total distance of 8.3 kilometers began on 22 October 2025, operating around the clock free-of-charge to the public. Civil works for the Ekkachai - Ban Phaeo Section are currently under construction with 90% of overall progress having been completed already (as of October 2025). Regarding system and operations and maintenance (O&M) works, the Department of Highways is in the process of selecting a private sector partner under a public-privatepartnership (PPP) scheme. The concession agreement is expected to be signed in 2026, with system installation scheduled to commence the same year and full commercial operations are planned for 2027.Section 3: Mueang Samut Sakhon District, Samut Sakhon Province, Sta. 24+670 - Sta. 25+734Section 9: Mueang Samut Sakhon District, Samut Sakhon Province, Sta. 33+366 - Sta. 35+511Completed Sections68 Annual Report 2025 Department of Highways

Section 1: Mueang Samut Sakhon District, Samut Sakhon Province, Sta. 20+295 - Sta. 22+474Section 2: Mueang Samut Sakhon District, Samut Sakhon Province, Sta. 22+474 - Sta. 24+670Section 4: Mueang Samut Sakhon District, Samut Sakhon Province, Sta. 25+734 - Sta. 26+998Sections under ConstructionToll rates for Inter-city Motorway No. 82(Bang Khun Thian - Ban Phaeo)Annual Report 2025 Department of Highways 69

ARCHITECURE1. Development of Access Routes to Tourist AttractionsLandscape Improvement on Highway No. 1020, Ban Plong - Chomphu Section (Sta. 87+663 - Sta. 93+424), Chiang Rai Highway District 2Project BackgroundThe project is located on Highway No. 1020, a gateway to Phu Chi Fa, a well-known tourist destination in Chiang Rai Province. Previously, the site was a barren median strip without any landscaping or trees, requiring improvement and aesthetic enhancement to promote the area’s image and point visitors to tourist attractions in the Phu Chi Fa area.Project ScopeThe project is located on the median at the intersection of Highway No. 1020 and Highway No. 1421, near the entrance gate to Phu Chi Fa (Rural Road No. 4018).Benefits1. Creates a visual landmark and provides navigation to tourist attractions.2. Showcases local cultural identity, fostering greater appreciation of community activities.Highway Landscape and Architecture Development70 Annual Report 2025 Department of Highways

2. Green Space EnhancementLandscape Improvement on Highway No. 1386, Phitsanulok Airport Access Road Section (Sta. 0+000 - Sta. 2+220), Phitsanulok Highway District 13. Rest Area DevelopmentLandscape Improvement on Highway No. 212, Amnat Charoen - Nong Yo Section (Sta. 533+700), Ubon Ratchathani Highway District 1Project BackgroundThe project is located on Highway No. 1386 at an interchange that serves as egress to the airport; it is encompassed by residential communities and traffic volume is high. This location functions as a gateway to Phitsanulok City for air travelers, as it is frequently seen by tourists driving by from the airport, making it a prime location for landscape improvement to enhance its aesthetic appeal.Project Scope The project is located at an interchange that serves as an access point to the airport. The site is suitable for landscape improvement to enhance its aesthetic appearance.Benefits Enhances the scenic value of the area and makes it safer; the creation of more green space improves both the Department of Highways’ and Phitsanulok Province’s public image.Project BackgroundThe project is located on Highway No. 212 at the Muang Sam Sip Highway Service Area. Highway No. 212 experiences heavy traffic volume, but the area has insufficient service points to provide road users with rest stops that are instrumental in attenuating potential accidents during travel.Project ScopeThis project involves landscape improvement to provide a comfortable rest area for road users. The area includes recreational space, rest shelters, and restrooms to serve drivers and local residents.Benefits 1. Provides a safe and comfortable rest area for road users2. Enhances the scenic value of the previously vacant land and makes it safer; the creation of more green space improves the Department of Highways’ public image.Annual Report 2025 Department of Highways 71

Survey and DesignAND DESIGNConsultancy Service for Survey and Design of a Four-Lane Highway on Highway No. 3486 (Ban Kut Toei - Ban Mai Thai Thawon) and Highway No. 348 (Ta Phraya District - Non Din Daeng District)Project BackgroundHighway No. 3486 and Highway No. 348 start from Highway No. 33 (Suwannason Road) in Aranyaprathet District, extend into Non Din Daeng District, Buri Ram Province, and terminate at Highway No. 24 (Det Udom Road). The section of Highway No. 3486 and Highway No. 348 passing through the Khao Chong Tako area is a key corridor connecting the eastern region with the upper and lower northeastern regions. The section features a two-lane road with steep gradients and horizontal curves that present safety risks. The route has heavy traffic volumes and experiences frequent accidents, so the safety of road users is compromised. Project Objectives1. Supports smoother travel, boosts tourism, and facilitates freight transportation.2. Mitigates road accidents and improves or addresses high-risk locations to ensure travel safety.3. Detailed engineering designs that consider environmental impact mitigation for sustainable development and environmental oversight.Project AlignmentThe project alignment comprises two main highways: Highway No. 3486 and Highway No. 348, currently configured as two-lane and four-lane road sections spanning 47.96 kilometers, as illustrated below. The project corridor connects Sa Kaeo Province and Buri Ram Province, traversing residential areas, Ta Phraya National Park, and Dong-Yai Wildlife Sanctuary. Project route alignment is summarized hereunder:A preliminary survey indicated that the proposed alignment traverses environmentally sensitive areas; therefore, an Environmental Impact Assessment (EIA) report is required in accordance with the Notification of the Ministry of Natural Resources and Environment.72 Annual Report 2025 Department of Highways

Overview of Development Design to Minimize Environmental Impacts on the World Heritage Dong Phayayen - Khao Yai Forest Complex Overview of Highway No. 348(Sta. 73+000 - Sta. 82+000)The section of Highway No. 348 extends from the Khao Chong Tako area to the Ta Phraya National Park, part of the Dong Phayayen - Khao Yai Forest Complex. The development follows the existing alignment of Highway No. 348 with minor realignments between Sta. 77+300 and Sta. 80+200. The project widens the road from two lanes to four lanes with concrete surfacing and improves horizontal curve radii at the selected locations. Due to the mountainous terrain and significant elevation differences at the beginning and end of the section, the design includes reducing the vertical gradients compared to the existing two-lane configuration. Climbing and descending sections are interspersed with transition segments to moderate vehicle speeds, thereby enhancing overall traffic safety.Development Design of Highway No. 348(Sta. 73+000 - Sta. 82+000)The section begins with an at-grade highway, then the alignment transitions to an elevated structure commencing from Sta. 75+750 to Sta. 79+875, with a total length of 4.125 kilometers. This elevated design separates traffic from the forest ground below, thus preserving the space beneath the structure to maintain ecological connectivity. The underpass area allows wildlife to move freely in forest areas on both sides of the corridor, thereby reducing the risk of collisions between road users and wildlife. Subsequently, a cut-and-cover tunnel structure was proposed between Sta. 79+925 and Sta. 80+225, with a total length of 300 meters. The tunnel is designed to ensure complete separation between the traffic corridor and forest connectivity areas.Project visualization of elevated viaduct along the entire Khao Chong Tako SectionProject visualization of cut-and-cover tunnel sectionat Sta. 79+925 to Sta. 80+225Annual Report 2025 Department of Highways 73

Development Design of Highway No. 348(Sta. 93+400)The Non Din Daeng District Section of Highway No. 348 in Buri Ram Province passes through the Dong-Yai Wildlife Sanctuary, where frequent vehicle collisions with wild elephants have occurred as the beasts forage intrusively in nearby communities and arable areas. To mitigate these accidents, an overpass structure construction has been planned at Sta. 93+400 to allow elephants and other large wildlife to pass safely beneath the highway. The structure will feature two lanes in each Wildlife crossing structure at Dong-Yai Wildlife Sanctuary (Sta. 93+40)direction with a maximum gradient of 4%, along with wildlife control fencing installed beneath and along the structure.Project completion will enhance the efficiency of the transportation network linking the Eastern and lower Northeastern Regions. It will improve travel convenience, traffic flow, and safety; reduce collisions between road users and wildlife; accommodate future traffic growth; and support economic and tourism development within the project area and the region.74 Annual Report 2025 Department of Highways

Land AcquisitionOWNERSHIPLand Acquisition for the Construction of Highway No. 425 (Hat Yai Outer Ring Road)Project BackgroundLocated in Songkhla Province, bordering Malaysia, Hat Yai District is a major economic and commercial hub, particularly in terms of trade, services, and tourism, especially international visitors from Malaysia and Singapore. As a key transportation corridor for the lower southern region of Thailand, such development has led to steadily increasing travel demand. Traffic volumes now exceed the capacity of the existing road network, causing congestion, travel delays, and higher time and transportation costs for both freight and motorist movements. In this context, the conditions have adversely affected logistics efficiency, economic performance, and residents’ quality of life. Travel within and around Hat Yai City has become more inconvenient and riskier, with the situation expected to deteriorate due to deficient attention to infrastructure improvement. To address these issues, the Department of Highways has planned the construction and improvement of Highway No. 425 (Hat Yai Outer Ring Road), totaling 66.84 kilometers encompassing both the eastern and western sections. The 31.33-kilometer eastern section extends from Ban Thung Nam, connecting Highways No. 407, No. 43, and No. 4 to Hat Yai International Airport. The 35.51-kilometer western section joins the main highway network and Inter-city Motorway No. 84 (Hat Yai-Thai/Malaysian Border) or M84. The project begins in Na Mom District, passes through Bang Klam District, and terminates in Hat Yai District in Songkhla Province.Currently, the eastern section of Highway No. 425 (Hat Yai Outer Ring Road), from Sta. 0+000 to Sta. 31+331.426, has three phases: Section 1 (Sta. 24+148 -Sta. 31+331), for which a Royal Decree on land acquisition has already been promulgated, Section 2 (Sta. 17+542 - Sta. 24+153), currently under implementation procedures, and Section 3 (Sta. 0+000 - Sta. 17+542), which has yet to be initiated. The western section is a new alignment of approximately 35 kilometers, beginning at the intersection with Highway No. 4135 (Sta. 8+850) in Ban Khuan and terminating at the intersection with Highway No. 414 (Sta. 11+635.236) in Ban Nong Sai. This section is designed as a four-lane highway to ease traffic congestion in Hat Yai City. It includes connections to the existing road network to ensure convenient travel, and an interchange at Highway No. 414 to ensure uninterrupted traffic flow without signal control.Considered a priority project, land acquisition and compensation payments must proceed without delay to avoid construction disruptions. This process requires a significant number of personnel with expertise in land surveying and valuation for assets within the right-ofway. The Bureau of Right of Ways has undertaken land expropriation procedures for more than 1,100 affected cases to ensure the project achieves its objectives and to hand over the right-of-way for subsequent construction.Annual Report 2025 Department of Highways 75

Project ImplementationThe Bureau of Right of Ways recognizes the importance of and need to expedite land acquisition procedures to support the construction of Highway No. 425 (Hat Yai Outer Ring Road, Eastern Section). A Royal Decree establishing the land expropriation zone for the section from Sta. 24+148 to Sta. 31+331 came into force on 24 May 2022, followed by an urgent notification issued on 18 November 2025. Throughout the project corridor, more than 1,100 property owners have been affected, covering land, structures, and orchards and crops. Currently, compensation payments have been completed for over 90% of the owners.In carrying out the process, land acquisition officers conducted public meetings to provide clarification and ensure mutual understanding. The project’s necessity and urgency, aligned with government policy, were explained along with legal and fair criteria for determining compensation. The efforts focused on minimizing impacts, reducing potential conflicts, and upholding fairness and transparency throughout the process. Land acquisition is thus a critical supporting function to keep construction on schedule. Continuous communication has fostered public understanding and acceptance, while highlighting the benefits of the project, such as improved transportation efficiency and potential increase in land value. As a result, cooperation from landowners and occupants has been achieved, with minimal resistance or obstruction to official operations. Public participation meetingTo date, the route has been integrated into the planned development of the western Hat Yai bypass road network connecting to Malaysia through Inter-city Motorway M84 (Hat Yai-Thai/Malaysian Border). The project links Hat Yai with the Sadao Customs House 2, located within the Songkhla Special Economic Zone. It aims to enhance transportation efficiency, promote tourism, trade, and investment, alleviate traffic congestion, and support the continued expansion of the special economic zone. The Bureau of Right of Ways has fulfilled its responsibilities in strict compliance with applicable laws and regulations, with due regard to the interests of both the public and the government. Consequently, the construction of Highway No. 425 (Hat Yai Outer Ring Road) has proceeded in accordance with the established project timeline, without delays from land acquisition issues or complaints from expropriated property owners.76 Annual Report 2025 Department of Highways

Project visualization of Highway No. 425 (Hat Yai Bypass)BenefitsTo enhance connectivity of the highway network surrounding Hat Yai District and respond to ongoing urban and economic expansion in the district and adjacent areas, where residential, commercial, and industrial development continues to intensify, the project aims to improve overall transportation efficiency. It facilitates convenient and rapid interconnections to support economic activities, reduce traffic congestion in Hat Yai District, and ensure smoother, faster, and safer travel. Additionally, the project promotes local transportation and logistics systems, which support both economic growth and the quality of life of the public, and improve mobility within and around Hat Yai. Therefore Hat Yai’s role as a key transportation hub of the lower southern region is boosted and residents enjoy sustainable urban development and improved quality of life.Annual Report 2025 Department of Highways 77

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Highway No. 12, Adjacent to Chao Pho Phawo Shrine, Mae Sot District, Tak ProvinceAnnual Report 2025 Department of Highways 79

AND INSPECTIONMaterial Analysisand Inspection 1. Subsurface void detection using GPR on Highway No. 31 following sidewalk settlementOn 9 March 2025, soil layer settlement on Highway No. 31 (Vibhavadi Rangsit Road) at Sta. 7+945 (left-hand side) caused sidewalk collapse over a length of 5 meters and a depth of approximately 0.8 meters. The incident was caused by leakage from the retaining wall, leading to the loss of backfill sand and subsequent settlement of the sidewalk surface.The following day, 10 March 2025, the Bureau of Material Analysis and Inspection conducted a Ground Penetration Radar (GPR) survey to identify the potential subsurface voids in the sidewalk and its vicinity.The subsurface void investigation using GPR with a 400 MHz radar frequency along the sidewalk of Highway No. 31 (Vibhavadi Rangsit Road), Din Daeng -Ngam Wong Wan Section, between Sta. 5+000 and Sta. 9+000 on both sides, identified several subsurface voidlike anomalies in nearby locations. These findings will be used for monitoring, remedial planning, and preventive measures to mitigate potential future settlement risks.Area of sidewalk settlementand GPR subsurface void detectionGPR survey lines and locations of detected anomaliesor suspected subsurface voids80 Annual Report 2025 Department of Highways

Project location of Inter-city Motorway No. 81 (Bangkok - Kanchanaburi), Section 122. Recommendation on the use of EPS foam for bridge approach construction on soft soil for Inter-city Motorway No. 81 (Bangkok - Kanchanaburi), Section 12 (Sta. 38+500.000 - Sta. 44+266.833)The Bureau of Material Analysis and Inspection, through the Material Control and Supervision Group, is responsible for verifying the quality of materials used in highway construction, designing mix proportions, and recommending the appropriate material used to ensure compliance with required standards and specifications. The division also provides technical guidance to address construction-related engineering issues. In line with this mandate, the director and the head of the advisory team have conducted regular site visits to monitor field operations, identify construction challenges, and provide technical recommendations to ensure successful project implementation in accordance with project objectives.The Inter-city Motorway No. 81 (Bangkok - Kanchanaburi) or M81 project carried out by the Department of Highways aims to enhance transportation connectivity between Bangkok and its environs and the Western Region of Thailand. The project is designed to accommodate increasing traffic demand in the future in line with the Inter-city Motorway Master Plan. Under the construction contract for Section 12 (Sta. 38+500.000 -Sta. 44+266.833), bridges are being constructed at Sta. 41+174.866 (left-hand side) and Sta. 41+171.248 (righthand side) with a 2.6-meter vertical clearance. When the bridge abutments and sand embankments at the bridge approaches over the bearing unit pile structure neared completion, the Nakhon Pathom Municipality and local residents requested an increase in the vertical clearance to 4.5 meters to accommodate large trucks. This required raising the embankment by approximately 5.5 meters, increasing lateral earth pressure on the existing bridge abutments and reducing embankment stability, posing structural damage risks. To mitigate these impacts, the designer proposed reducing the backfill weight behind the abutments using lightweight expanded polystyrene (EPS) foam, a synthetic material significantly lighter than conventional sand backfill, to maintain adequate embankment stability and decrease lateral earth pressure on the abutment structure. The design elements included structural stability, strength requirements, and overall budget implications for implementation. Annual Report 2025 Department of Highways 81

For the site inspection of Inter-city Motorway No. 81 (Bangkok - Kanchanaburi), Section 12, the Bureau of Material Analysis and Inspection, via the Material Control and Supervision Group, collaborated with project personnel, including the project engineer, assistant project engineer, and supervising engineers. The inspection allowed the team to identify technical issues related to the modification of the bridge approach embankment. Based on available engineering data, such as soil investigation results, bridge and approach design blueprints, traffic information, vehicle volume and classification assessment, and construction cost, the division recommended revising the method by using EPS foam. As EPS foam is a high-cost material and approximately six times more expensive per unit than conventional sand embankment fill, the division recommended reducing its quantity owing to the construction cost. Following discussions with the designer, it was agreed to shorten the bridge approach length section using EPS foam instead of conventional sand fill. Beforehand, EPS foam was to be used to replace sand embankment over a length of 160 meters at both bridge approaches (four sides combined). The revised design reduced the EPS foam application to 18 meters per side, significantly reducing the additional construction cost associated with the modification. Throughout the work, strict quality control and material inspection were carried out, along with close supervision to ensure compliance with specifications and procedures. The bridge and approach embankment construction was successfully completed, ensuring structural stability and capacity to accommodate heavy truck traffic in line with road user needs.Cross section of the bridge at Sta. 41+173.631 (LT) and Sta. 41+170.377 (RT)Slope section of the bridge at Sta. 41+173.631 (LT) and Sta. 41+170.377 (RT)82 Annual Report 2025 Department of Highways

Example of soil-boring investigation data displayed on Google My Maps3. Storage of soil-boring investigationdata using coordinate pins on Google My MapsThe online mapping technology, Google My Maps, is useful to store and disseminate borehole coordinate data, boring logs, location maps, cross sections, and photographs. By integrating all relevant information into a single platform, it offers users convenient, efficient, and systematic data access and retrieval. This is a vast improvement on the past, when data were typically stored in report documents or separate files, often leading to difficulties in data management, delayed retrieval, and limitations in interagency data sharing. As such, previously collected data could not always be utilized promptly in response to urgent situations.To overcome these limitations, the Bureau of Material Analysis and Inspection, via the Material and Pavement Evaluation Branch, has developed a guideline for storing and displaying soil-boring investigation data using online maps on the Google My Maps platform. This tool is free of charge, accessible, and user-friendly; it facilitates data retrieval anytime and anywhere, while efficiently supporting spatial data management. The system enhances database accessibility, ensuring rapid and convenient information access when required. The data management procedures are described hereunder:1. Field data collection: Collect borehole coordinates, photographs, and boring logs2. Creation of Google My Maps2.1 Create a new map and assign a project title, such as “DOH Boring Log Map.”2.2 Pin the borehole coordinates onto the mapbased on field survey data.2.3 Attach relevant files, including boring logs,location maps, cross sections, and site photographs, in PDF or JPG format.3. Data dissemination: Share the online map via agenerated link that provides authorized access for officers or related personnel.4. Access and data maintenance: Regularly update data, verify accuracy, and practice data backupsto prevent data loss.Storing soil-boring investigation data as coordinate pins on the Google My Maps platform improves systematic data management. Users can easily search, review details, and verify borehole information via the website or shared links, without the need to manually retrieve multiple documents or file records as required under the conventional system. The key advantages of using Google My Maps as a soil-boring data management tool are:1. Data are systematically categorized and classified by area or project.2. The database is accessible anytime and anywhere with an internet connection.3. The platform supports collaboration, enabling officers and related personnel to analyze and utilize data from a single source, thereby reducing redundancy.4. Information dissemination is rapid and convenient, as links can be generated and embedded on the official website of the Department of Highways or other channels.5. Data can be easily added or updated, edited, and modified by authorized personnel without requiring specialized internet expertise.6. The system supports navigation functions, allowing coordinate pins to provide direct route guidance to actual borehole locations via Google My Maps.Annual Report 2025 Department of Highways 83

Roadwork Researchand Development DEVELOPMENTData Collection for Pavement Friction Analysis to Improve Road Safety StandardsThe Bureau of Road Research and Development, Department of Highways, is principally responsible for conducting research and development in terms of highway engineering. Studies indicate that road accident statistics in Thailand are high. Among the contributing factors identified are unsafe road conditions, in particular slippery pavement surfaces or inadequate skid resistance between the pavement surface and vehicle tires. To further enhance road safety, the Department of Highways requires sufficient data on the coefficient of friction (µ) to support maintenance planning in conjunction with other relevant parameters. Nowadays, most vehicles are equipped with an on-board diagnostics (OBD) port that monitors internal vehicle systems, issues warnings, and transmits driving data to provide insights into engine performance and vehicle safety information. Such data include engine speed, fuel consumption, braking behavior, and braking force used to stop the vehicle. These parameters are standardized under automotive manufacturing regulations, ensuring accuracy and reliability. In this context, the Bureau of Road Research and Development, initiated a study to analyze OBD data and to examine its correlation with pavement friction values measured by internationally standardized testing equipment and data derived from OBD. The objective is to evaluate whether OBD-based surveys can provide a preliminary assessment of skid resistance and support maintenance planning, thereby improving operational efficiency and road safety.This study developed a prototype data acquisition system comprising an OBD reader (Vgate vLinker FS), a processing unit (Raspberry Pi), a GPS module, and an accelerometer; the set was installed in a standard test vehicle (Toyota Revo) for field operations. Field testing was conducted on 90 road sections nationwide, covering approximately 450 kilometers. The experimental program included four test conditions: acceleration and deceleration under dry and wet pavement conditions. OBD data, such as wheel speed and acceleration, were analyzed and compared with pavement friction values measured using the Department of Highways’ standard equipment, ASFT T-10, and the Dynamic Friction Tester (DFT). Preliminary results from the first phase (30 sections) indicated that the deceleration method under wet conditions yielded the highest correlation with standard friction measurements and was therefore adopted for the main study phase.Wet deceleration field testing• Relationship model between the coefficient of friction and OBD-measured variablescoefficient of friction (µ) = -0.00698 + 0.00221(X6) -0.00003(X7)X6 = Mean value of the squared difference between front and rear wheel speedsE7 = Mean acceleration/deceleration measured by the accelerometer • The model yields a coefficient of determination (R2) of 0.675 when compared with friction values obtained from the T-10 standard testing equipment, with a Mean Absolute Percentage Error (MAPE) of 17.87%.84 Annual Report 2025 Department of Highways

Bridge Strengthening of Existing Prestressed Concrete I-girder Bridges Using Life-cycle Cost Analysis Comprehensive construction of prestressed concrete (PC) I-girder bridges in Thailand started in 1972. Due to ease of construction and simplicity in inspection, this type of bridge is found nationwide. However, with increasing truck weight spectra, the design load has been updated. This results in more than 300 Department of Highways’ PC I-girder bridges rated structurally deficient.In this study, retrofit methods for old 18-meter, 22-meter, 26-meter, and 30-meter PC I-girders to cost-effectively meet the present AASHTO HL-93 design loads were assessed. Three strengthening methods were proposed for girders i.e., additional prestressing, high strength rebar strengthening, and use of Carbon Fiber Reinforced Polymer (CFRP) materials. For decks, only reconstruction was considered. The combination of girder and deck strengthening methods that yield minimum life-cycle cost with respect to extended service life is considered to be the most cost-effective strengthening scheme. Life-cycle cost includes initial strengthening cost, future deck reconstruction cost, and the construction cost of new bridges (girders and decks only) when it is determined that the girders have deteriorated to an unacceptable level of performance. The deterioration process considered was fatigue damage due to truck traffic. Fatigue curves of reinforced concrete (RC) decks and prestressed concrete (PC) girders in previous studies were used to capture the deterioration process. Cored sampling and in-field bridge load tests as well as truck traffic forecasts were executed to supplement the fatigue analysis. The Department of Highways may apply the study outcomes to further strengthen its operational framework by deploying the developed equipment to screen road sections at risk of slippery pavement conditions.This innovation enables the department to conduct rapid and cost-effective preliminary assessment of pavement skid resistance, thereby supporting the Department of Highways’ preventive maintenance strategies.ผ่่านเกณฑ์์ปรัับปรุุงแก้้ ไขที่่�ความเชื่่�อมั่่�น 95%ตรวจสอบด้้วยอุุปกรณ์์ทดสอบความเสีียดทานกล่่องประมวลผลผ่่าน OBD วิิเคราะห์์ข้้อมูลูการใช้้งานอุุปกรณ์์ค่่า MIN จากแบบจำลำองมากกว่่า 0.29 ใช่่แสดงสีีเขีียวไม่่ใช่่แสดงสีีเหลืืองEquipment utilization diagramOverview of the sample bridge and heavy truck traffic conditionsRoad pavement friction evaluation device via OBDNote: The road pavement friction evaluation device via OBD is currently pending petty patent application.Annual Report 2025 Department of Highways 85

Six sample bridges were investigated to demonstrate the analysis as tabulated below, covering various span lengths, heavy truck traffic (three axles or more), and bridge ages, to determine the most cost-effective strengthening schemes.Detailed design drawings and cost estimation of these six bridges were documented for future reference. It was found that the cost-effective strengthening scheme depends on span length, heavy truck traffic (three axles or more) as well as bridge age. The cost-effective strengthening schemes were tabulated for practical purposes as shown in the table hereunder. The table reveals that:1) The pre-tensioned 18-meter and 22-meter girders deteriorate faster than the post-tensioned 26-meter and 30-meter girders. The 22-meter girder has the most accelerated deterioration.2) High strength rebar strengthening of girders with no deck reconstruction is appropriate for bridges experiencing low heavy truck traffic.3) As heavy truck traffic increases, the need for girder strengthening and deck reconstruction becomes more evident–initially through the use of high strength rebars, followed by pre-stressing until ultimately the construction of a new bridge (girders and decks only) is undertaken.Field test of pre-stressing tendon tensionand bridge load under truck traffic79,560,000127,476,00018,906,00032,000,000816,00019,636,000954,0001,000,00030,000856,000765,0001,000,00030,000856,0007,572,0009,000,000288,0008,600,00020262026202620682026204320262045202620381,29654610932128939519981987200719941990197757,1913,08471,88915,1053,5317,4101) Bridge reconstruction1) Bridgereconstruction1) Girder with high strength rebar (HR)2) Bearing replacement3) Deck jointreplacement1) Deck reconstruction1) Girder with high strength rebar (HR)2) Bearing replacement3) Deck jointreplacement1) Deck reconstruction1) Girder with highstrength rebar (HR)2) Bearing replacement3) Deck jointreplacement1) Deck reconstruction1) Girder with additionalpre-stressing (PS)2) Bearing replacement3) Deck jointreplacement1) Deck reconstruction1. Chao Phraya River Bridge Hw. 346 Sta. 10+462 (LT) Pathum Thani Highway District2. Railway Overpass Hw. 225 Sta. 36+288 (LT) Nakhon Sawan Highway District (12 22-m spans and six 26-m spans)3. Lat Pla Khao Overpass Hw. 304 Sta. 13+047.48 Bangkok Highway District (31 18-m spans and one 26-m span)4. Railway Overpass Hw. 327 Sta.5+838 (LT) Chumphon Highway District (one 22-m span)5. Railway Overpass Hw. 201 Sta. 3+265 (LT) Nakhon Ratchasima Highway District 2 (one 22-m span)6. Nan River Bridge Hw. 11Sta. 326+950 (LT) Uttaradit Highway District 1 (nine 30-m spans)Bridge Name Yr. BuiltAADT HTT* Yr Items Cost** (Baht)Example of a strengthening design for an older-generation PC I-girder bridge under the Department of Highways86 Annual Report 2025 Department of Highways

Physical characteristics of Wutthikun BridgeRehabilitation of Wutthikun Bridge to Enhance Service Safety after 70 Years of OperationWutthikun Bridge that crosses Ping River in Tak Province is Thailand’s third historic bowstring bridge. The bridge comprises four main spans of bowstring (tied-arch) structures and three approach spans of simple T-beam structures. The overall length of the bridge is 248.70 (1x16.70+2x46.70+2x51.10+2x18.20) meters. The bridge has been operational since 1953.Wutthikun Bridge is still vital to Thailand’s road transportation. The bridge is located on the main route for the transportation of agricultural commodities. However, lately the bridge was showing signs of age after inspection so a weight restriction of 20 tons (200 kN) was posted. This restriction affects the transportation of agricultural commodities by 25-ton (250-kN) trucks and the bridge is prone to overloading. Wutthikun Bridge therefore requires immediate rehabilitation to ensure structural integrity and safety against transportation by 25-ton (250-kN) trucks and to preserve one of the most prominent engineering structures in Thailand’s history.Year builtYear builtYear builtYear built*3 axles or more PS-additional pre-stressing HR-high strength rebar strengthening Recon-reconstruction if necessary HR can be replaced with PS*3 axles or more PS-additional pre-stressing HR-high strength rebar strengthening Recon-reconstruction if necessary HR can be replaced with PS*3 axles or more PS-additional pre-stressing HR-high strength rebar strengthening Recon-reconstruction if necessary HR can be replaced with PS*3 axles or more PS-additional pre-stressing HR-high strength rebar strengthening Recon-reconstruction if necessary HR can be replaced with PS18 m 1972 - 1976 1977 - 1981 1982 - 1986 1987 - 1991 1992 - 1996 1997 - 200118 m 1972 - 1976 1977 - 1981 1982 - 1986 1987 - 1991 1992 - 1996 1997 - 200118 m 1972 - 1976 1977 - 1981 1982 - 1986 1987 - 1991 1992 - 1996 1997 - 200122 m 1972 - 1976 1977 - 1981 1982 - 1986 1987 - 1991 1992 - 1996 1997 - 2001201 - 300 Girder Deck Girder Deck Girder PS 2026 Girder PS 2026 Girder PS 2026 Girder PS 2026Recon 2026 Recon 2026 Deck Recon 2044 Deck Recon 2044 Deck Recon 2045 Deck Recon 2045201 - 300 Girder Deck Girder Deck Girder PS 2026 Girder PS 2026 Girder PS 2026 Girder PS 2026Recon 2026 Recon 2026 Deck Recon 2044 Deck Recon 2044 Deck Recon 2045 Deck Recon 2045201 - 300 Girder Deck Girder Deck Girder PS 2026 Girder PS 2026 Girder PS 2026 Girder PS 2026Recon 2026 Recon 2026 Deck Recon 2044 Deck Recon 2044 Deck Recon 2045 Deck Recon 2045101 - 200 Girder PS 2026 Girder PS 2026 Girder HR 2026 Girder HR 2026 Girder HR 2026 Girder HR 2026Deck Recon 2026 Deck Recon 2026 Deck Recon 2053 Deck Recon 2053 Deck Recon 2053 Deck Recon 2053 101 - 200 Girder PS 2026 Girder HR 2026 Girder HR 2026 Girder HR 2026 Girder HR 2026 Girder HR 2026 Deck Recon 2026 Deck Recon 2053 Deck Recon 2053 Deck Recon 2053 Deck Recon 2054 Deck Recon 2054201 - 300 Girder Deck Girder Deck Girder Deck Girder Deck Girder HR 2026 Girder HR 2026Recon 2026 Recon 2026 Recon 2026 Recon 2026 Deck Recon 2045 Deck Recon 2045401 - 500 Girder Deck Girder Deck Girder Deck Girder Deck Girder Deck Girder PS 2026Recon 2026 Recon 2026 Recon 2026 Recon 2026 Recon 2026 Deck Recon 2035401 - 500 Girder Deck Girder Deck Girder Deck Girder PS 2026 Girder PS 2026 Girder HR 2026Recon 2026 Recon 2026 Recon 2026 Deck Recon 2033 Deck Recon 2034 Deck Recon 2035401 - 500 Girder Deck Girder Deck Girder PS 2026 Girder PS 2026 Girder HR 2026 Girder HR 2026Recon 2026 Recon 2026 Deck Recon 2033 Deck Recon 2033 Deck Recon 2034 Deck Recon 20351 - 100 Girder PS 2026 Girder PS 2026 Girder PS 2026 Girder PS 2026 Girder HR 2026 Girder HR 20261 - 100 Girder HR 2026 Girder HR 2026 Girder HR 2026 Girder HR 2026 Girder HR 2026 Girder HR 2026Deck Recon 2069 Deck Recon 20691 - 100 Girder HR 2026 Girder HR 2026 Girder HR 2026 Girder HR 2026 Girder HR 2026 Girder HR 2026Deck Recon 2069 Deck Recon 2070 Deck Recon 2070 Deck Recon 2070 Deck Recon 2070 Deck Recon 20701 - 100 Girder PS 2026 Girder HR 2026 Girder HR 2026 Girder HR 2026 Girder HR 2026 Girder HR 2026101 - 200 Girder PS 2026 Girder PS 2026 Girder PS 2026 Girder PS 2026 Girder PS 2026 Girder PS 2026Deck Recon 2053 Deck Recon 2054 Deck Recon 2054101 - 200 Girder Deck Girder Deck Girder HR 2026 Girder HR 2026 Girder HR 2026 Girder HR 2026Recon 2026 Recon 2026 Deck Recon 2054301 - 400 Girder Deck Girder Deck Girder Deck Girder Deck Girder PS 2026 Girder PS 2026Recon 2026 Recon 2026 Recon 2026 Recon 2026 Deck Recon 2039 Deck Recon 2039301 - 400 Girder Deck Girder Deck Girder PS 2026 Girder PS 2026 Girder HR 2026 Girder HR 2026Recon 2026 Recon 2026 Deck Recon 2038 Deck Recon 2038 Deck Recon 2039 Deck Recon 2039301 - 400 Girder Deck Girder PS 2026 Girder PS 2026 Girder HR 2026 Girder HR 2026 Girder HR 2026Recon 2026 Deck Recon 2037 Deck Recon 2038 Deck Recon 2038 Deck Recon 2039 Deck Recon 2039301 - 400 Girder Deck Girder Deck Girder Deck Girder Deck Girder Deck Girder HR 2026Recon 2026 Recon 2026 Recon 2026 Recon 2026 Recon 2026 Deck Recon 2039Heavy truck traffic* (veh/day/dir.) 2025 Heavy truck traffic* (veh/day/dir.) 2025 Heavy truck traffic* (veh/day/dir.) 2025 Heavy truck traffic* (veh/day/dir.) 2025 501 - 600 Girder Deck Girder Deck Girder Deck Girder Deck Girder Deck Girder PS 2026Recon 2026 Recon 2026 Recon 2026 Recon 2026 Recon 2026 Deck Recon 2031501 - 600 Girder Deck Girder Deck Girder Deck Girder Deck Girder PS 2026 Girder HR 2026Recon 2026 Recon 2026 Recon 2026 Recon 2026 Deck Recon 2031 Deck Recon 2031501 - 600 Girder Deck Girder Deck Girder Deck Girder PS 2026 Girder HR 2026 Girder HR 2026Recon 2026 Recon 2026 Recon 2026 Deck Recon 2033 Deck Recon 2034 Deck Recon 2035601 - 700 Girder Deck Girder Deck Girder Deck Girder Deck Girder PS 2026 Girder HR 2026Recon 2026 Recon 2026 Recon 2026 Recon 2026 Deck Recon 2026 Deck Recon 2029601 - 700 Girder Deck Girder Deck Girder Deck Girder Deck Girder PS 2026 Girder HR 2026Recon 2026 Recon 2026 Recon 2026 Recon 2026 Deck Recon 2026 Deck Recon 2029701 - 800 Girder Deck Girder Deck Girder Deck Girder Deck Girder Deck Girder HR 2026Recon 2026 Recon 2026 Recon 2026 Recon 2026 Recon 2026 Deck Recon 2026701 - 800 Girder Deck Girder Deck Girder Deck Girder Deck Girder HR 2026 Girder HR 2026Recon 2026 Recon 2026 Recon 2026 Recon 2026 Deck Recon 2026 Deck Recon 2026801 - 900 Girder Deck Girder Deck Girder Deck Girder Deck Girder Deck Girder HR 2026Recon 2026 Recon 2026 Recon 2026 Recon 2026 Recon 2026 Deck Recon 2026801 - 900 Girder Deck Girder Deck Girder Deck Girder Deck Girder Deck Girder HR 2026Recon 2026 Recon 2026 Recon 2026 Recon 2026 Recon 2026 Deck Recon 2026901 - 1000 Girder Deck Girder Deck Girder Deck Girder Deck Girder Deck Girder HR 2026Recon 2026 Recon 2026 Recon 2026 Recon 2026 Recon 2026 Deck Recon 2026Annual Report 2025 Department of Highways 87

Detailed design for the rehabilitation of Wutthikun Bridge to meet the current AASHTO LRFD 2020 Specifications was carried out. The existing condition of the bridge was examined to supplement the finiteelement models in the evaluation and design process. The examination process included bridge profiling, concrete scanning, damage evaluation, cored sampling, load testing, and foundation survey. It was concluded from the finite-element analyses that for the main spans, concrete jacketing is required for the arch ribs; concrete jacketing and pre-stressing is required for the tension girders; all hangers need replacing; and deck reconstruction is also required. For the approach spans, concrete jacketing and pre-stressing is also required for the beams and, as noted, reconstructionis also required for the decks. All concrete surfaces exposed to air should be painted with anti-aging agents for mitigating carbonation. Bridge bearings and joints in all spans require replacement. Bridge foundations require scour protection with Gabion boxes. In addition, a long-term structural health monitoring system and bridge lighting system are also warranted. Detailed drawings, inspection and maintenance plans, and cost estimation were documented. The rehabilitation cost is approximately 480 million baht (as of March 2025). The aforementioned price does not include the cost of an additional structural strength inspection prior to the start of restoration.The examination of Wutthikun Bridge indicated that there was a considerable amount of damage; load distribution in tied-arch spans was anomalous due to the misalignment of the hangers; the concrete was deteriorating, with carbonation penetrating beyond the cover depth of the reinforcing bars, indicating a risk of corrosion. Bridge foundations on the Tak side showed evidence of scouring. The bridge is, however, still stable and there is no evidence of settling. Field test for the bridge load under truck traffic,and investigation of reinforcement details using concrete surface scanning with GPRBridge structural damage and finite-element analysisBlueprint for the rehabilitation of Wutthikun BridgeBridge after rehabilitation and installationof a lighting system88 Annual Report 2025 Department of Highways

Truck-induced fatigue cracks on the bridge deck and an image of crumb rubberSpecimen bridge deck models and finite-element modelsMitigating Bridge Deck Fatigue Cracking Using Crumb Rubber ConcreteA typical bridge consists of a deck slab, girders, piers, and footings, which work together to resist traffic loads. Due to direct contact with traffic loads, the deck slab is the element that is most vulnerable to damage.Truck-induced fatigue cracking typical damage to the deck slab. Fatigue strength generally improves as the static strength of a structure increases. Therefore, to attenuate fatigue cracking of the deck slab, its static strength has to be increased. This is typically done by increasing slab thickness or reducing girder spacing. However, both remedies have two drawbacks. First, increasing slab thickness or reducing girder spacing causes an unnecessary increase in static strength of the deck slab; due to the effect of membrane action inherent in the slab-on-girder system, the static strength of the deck slab is already increased well above the maximum design wheel load. Second, increasing slab thickness or reducing girder spacing adds more dead weight to the structure; this results in unnecessary higher construction cost for a bridge as a whole. A more appropriate method for increasing the fatigue strength of the deck slab is required. This can be accomplished via direct enhanced fatigue strength of the deck slab, i.e., replacement of sand with crumb rubber (25% by volume in this study). This mix is recommended by previous research on the same subject in China.Evaluation of crumb rubber in mitigating truckinduced fatigue cracks in deck slabs was conducted. Full-scale models of concrete deck slabs with the crumb rubber replacement of sand (25% by volume) were tested under both static and cyclic loadings and compared with the standard ones. Adding crumb rubber to the concrete mixing reduces the concrete strength which results in a drop of failure load (static strength) of the deck slab. However, the dropped failure load is still well above the maximum design wheel load so there is no concern about the load carrying capacity. The benefit of adding crumb rubber to the concrete mixing is the ductility gained which results in better performance of the deck slab under cyclic loads (fatigue strength). The crumb rubber deck slab can substantially mitigate truck-induced fatigue cracking.Annual Report 2025 Department of Highways 89

Ultimate compressive strength, Pu (tons),of a conventional concrete bridge deckMinimum required bridge deck thickness (meters)Maximum bridge girder spacing (meters)Fatigue curves for determining the minimum requiredbridge deck thicknessBridge girder spacing (meters)Bridge deck thickness (meters)0.150.160.170.180.190.202.0044.851.456.663.768.672.21.9048.254.459.566.370.774.51.8050.656.161.067.370.975.01.7058.464.469.676.680.484.51.6063.469.574.781.785.389.51.5069.675.881.288.592.096.3Standard concrete deck slab0.150.160.170.180.190.20-1.52*1.59*1.69*1.74*1.79*1.78**1.98**2.05***2.18***2.28***2.35*** Bridge deck thickness (meters)Crumb rubber concrete deck slabStandard concrete deck slab1.501.601.701.801.902.000.160.180.190.21*0.21*0.22*0.150.150.150.160.160.17Girder spacing (meters)Crumb rubber concrete deck slabFatigue curves were developed; and in combination with finite-element models and code recommendations, the recommended thicknesses of the crumb rubber deck slab (concrete compressive strength of 300 kg/cm2or 30 MPa) for practical ranges of girder spacing were analyzed. The analyses showed the potential of utilizing crumb rubber concrete for deck slab construction. For example, in the case of girder spacing of 2.00 meters, the required minimum thickness of the crumb rubber concrete deck slab is 0.17 meters as compared with 0.22 meters for the normal concrete deck slab; and for the same thickness of 0.20 meters, the maximum possible girder spacing when utilizing the crumb rubber concrete deck slab can be extended to 2.35 meters while for the standard one the maximum possible girder spacing is only 1.79 meters.Crumb rubber is an inexpensive locally available material. The proportion of 25% by volume of sand causes no difficulty in the mixing process. Crumb rubber concrete explicitly enhances fatigue strength of the deck slab. Implicitly, the crumb rubber concrete deck slab can reduce bridge construction cost due to its lower minimum required thickness or its greater maximum possible girder spacing. Additionally, utilizing crumb rubber promotes the reduction of toxic waste. It is therefore recommended as construction material for the Department of Highways’ deck slabs.90 Annual Report 2025 Department of Highways

COMMUNICATIONMechanical Equipment and Communications 1. Procurement of Machinery for the Fiscal Year 20252. Seminar on Enhancement of Mechanical Engineers’ Capacity under the Department of Highways Working CapitalIn the fiscal year 2025, the Bureau of Mechanical Equipment and Communications procured 16 heavy machinery units under the approved capital investment framework of the Department of Highways’ equipment revolving fund, with a total budget of 412,943,000 baht. The investment prioritizes heavy machinery to enhance construction efficiency, ensure compliance with standards, and improve road user safety. The five key units were:1) Vibratory rollers with steel wheels (minimum 25 tons) (2 units), procured to improve pavement compaction efficiency and strength, to be piloted at the Khon Kaen and Songkhla road construction training centers.2) 150-horsepower motor graders (5 units), procured to accommodate increased construction workloads assigned to road construction training centers.3) Dump trucks with diesel engines (10-ton, 10-wheel configuration) (5 units), procured to support expanded road construction missions at road construction training centers.4) Hydraulic excavators (minimum 150 horsepower) with hydraulic breaker attachments (5 units), procured to meet growing road construction needs at road construction training centers.5) Truck cranes (minimum 30-ton capacity) (4 units), procured to support increased construction and bridge rehabilitation works at bridge construction and rehabilitation centers.All procurement projects included initial operator training and maintenance training for technical staff to ensure proper machine operation and maintenance.In collaboration with the Training Division, the Bureau of Mechanical Equipment and Communications organized this seminar for the fiscal year 2025, with 58 participants. The seminar was held from 9-13 June 2025 at the bureau’s office, Chaeng Watthana Road, Pak Kret District, Nonthaburi Province and Bay Beach Resort Jomtien, Bang Lamung District, Chon Buri Province. The seminar aimed to improve engineering standards and operational guidelines for effective machinery management under the working capital. Key objectives were practical training on the proper, engineeringcompliant use of cranes and lifting equipment as well as training of mechanical engineers to conduct accurate inspections and to further train operators in their respective units. Emphasis was placed on regular inspections and maintaining operational readiness. This initiative supports standardized machinery management for road maintenance and construction, reduces operatorrelated accidents, and enhances public confidence in road safety.Annual Report 2025 Department of Highways 91

Meeting of the Cultural World Heritage Subcommittee on impact assessment guidelines for Si Satchanalai Historical Park in relation to the construction of Highway No. 102(Si Satchanalai District - Ban Don Ko), Sukhothai ProvinceJoint meeting with the Department of National Parks,Wildlife and Plant Conservation to discuss impactassessment for the proposed Andaman Sea Nature Reserves (World Heritage nomination) in relation to the construction of Highway No. 4 (Ban Ngao - Ban La-ong), Ranong ProvinceEnvironmental Protectionand Public Participation 2. Environmental quality assessment for 18 highway projects• A bridge over Sukhrip Canal on Highway No. 3(Sta. 112+875), Chon Buri Province• Highway No. 4034 (Pak Nam Krabi - Khao Thong), Krabi Province• Highway No. 34 (Bang Wua - Intersection with Highway No. 314, Khlong Om), Chachoengsao Province• New alignment connecting the Eastern Outer Ring Road Interchange to Highway No. 352, Pathum Thani Province• Interchange at the junction of Highway No. 22 with Highway No. 241 and Highway No. 2347 (Ban That Na Weng Intersection), Sakon Nakhon ProvinceRecognizing the importance of mitigating environmental and social impacts arising from highway development, the Department of Highways now has a policy to promotesustainable development. This policy emphasizes transparent, fair, and auditable operations while providing opportunities for public participation in the highwaydevelopment process. These efforts align with the National Environmental Quality Promotion and Conservation Act, B.E. 2535 (1992) and its amendment No. 2, B.E. 2561 (2018). The environmental framework is currently incorporated into Strategy 5: Motivating Research and Innovation to Develop Environmentally Friendly and Inclusive Highways under the Department of Highways Action Plan (B.E. 2566-2570 / 2023-2027), with the objective of achieving sustainable highway development.Over the past year, the Department of Highways has advanced infrastructure development juxtaposed by environmental protection and public participation to ensure a balanced and sustainable approach to development as well as the well-being of Thai society. Details are provided hereunder:1. Preparation of Environmental Impact Assessment (EIA) reports for eight highway projects• Highway No. 102 (Si Satchanalai District - Ban Don Ko), Sukhothai Province• Highway No. 4 (Ban Ngao - Ban La-ong), Ranong Province• Highway No. 108 (Mae Klang Bridge - Ban Bo Kaeo), Chiang Mai Province• Highway No. 41 (Pathom Phon Intersection - Ban Khao Bo), Chumphon ProvinceForward to Green: Green Highways for a Sustainable Future92 Annual Report 2025 Department of Highways

• Railway Overpass at Highway No. 226, Sta. 62+886, (adjacent to Surin Highway District area) - Uthumphon Phisai Intersection at Sta. 75+971, Si Sa Ket Province• Interchange at the junction of Highway No. 24 and Highway No. 224 (Chok Chai Intersection), NakhonRatchasima Province• The road parallel to the bridge across the Chao Phraya River under the Western Bangkok Outer Ring Road Inter-city Motorway project (Bang Khun Thian - Bang Pa-in)• Nakhon Ratchasima Ring Road from the intersectionof Highway No. 205 to the intersection of Highway No. 226, Nakhon Ratchasima Province• Railway overpass on Highway No. 4114, from the intersection of Highway No. 41 (Samo Thong) to the coast at Sta. 4+492, Surat Thani Province• Highway No. 333 (Nong Chang District - Uthai Thani), Nong Phai Subdistrict - Uthai Thani Section, Uthai Thani Province• Interchange at the junction of Highway No. 2 (Mittraphap Road) and municipal road/Chang Phueak Road (Pradok Intersection), and tunnel at the junction of Highway No. 2 and Highway No. 224 (Nakhon Ratchasima Intersection), Nakhon Ratchasima Province• Ang Thong Bypass, Ang Thong Province• Highway No. 304 (Chachoengsao - Khao Hin Son Subdistrict), Mueang Kao Subdistrict - Phanom Sarakham District Section, Chachoengsao Province• The construction of a four-lane Highway No. 304, Kabin Buri District - Pak Thong Chai District Section, Nakhon Ratchasima Province, and the wildlife corridor project on Highway No. 304, Kabin Buri District - Pak Thong Chai District Section, Prachin Buri Province• Highway No. 3702, Bang Khwai - Khao Din (bridge over the Bang Pakong River), Chachoengsao Province• Highway No. 4 (Pla Lang T-junction - Nuea Khlong District), Krabi Province• International highway network connection, Highway No. 101, Nan - Chaloem Phra Kiat District Section 2, Nan Province• Highway No. 103 (Rong Kwang District - Ngao District), Lampang Province• Highway No. 212 (Pak Khat District - BanSomprasong), Bueng Kan Province• Highway No. 226 (Ban Nong Sawai - BanRawiang), Surin ProvinceSustainable Public Engagement for Transparent Highway DevelopmentConstruction of highways passing through community areas on(Left) Highway No. 108 (Mae Klang Bridge - Ban Bo Kaeo)by Chiang Mai Highway District 1;(Right) Highway No. 306 (Khae Rai - Khlong Ban Mai)Khon Kaen Highway District 2 (Chum Phae)Construction projects for highway efficiency enhancement on (Left) Highway No. 3004 (Tha Tako - Dai Tan)by Nakhon Sawan Highway District 2 (Tak Fa);(Right) Highway No. 4071 (Kota Baru - Wang Phaya)by Yala Highway DistrictThe Department of Highways prioritizes publicinvolvement throughout all stages of highway development.To ensure transparency and engagement, publicparticipation activities are conducted, including publichearings during the construction phase, as mandated by the Prime Minister’s Office Regulations on PublicConsultation, B.E. 2548 (2005). These hearings facilitate the collection of public feedback and suggestions, which are incorporated to better align projects with local communityneeds. In 2025, the department conducted publicparticipation activities for 326 projects, categorized as follows:• 161 construction projects for highway efficiency enhancement• 60 projects for the construction of highwayspassing through community areas (for all user groups)• 105 large-scale construction projects allocated within the 2025 budgetAnnual Report 2025 Department of Highways 93

3. Engaged in environmental training programs.Workshop Participation:(Left) Inception Workshop on Sound Climate Investment forSustainable Transport Infrastructure Towards Thailand’s NDC Goals;(Right) Preparatory Meeting for Climate Change CooperationAction Plan(Left) The 4th Thailand Climate Action Conference(TCAC 2025): Inspiring Climate Solutions for All(Right) Participation in the Ad Hoc Committee Meetingon the Draft Act on Pollutant Releaseand Transfer Register (PRTR), B.E. …(Left) The Department of Highways participated in a consultation meeting on the development of Applied Strategic Environmental Assessment (SEA) guidelines for planning related toNatural World Heritage sites.(Right) The Department of Highways attended a workshop on Heritage Impact Assessments (HIAs) for World Heritage properties.(Left) Public training on Carbon Footprint forOrganization (CFO)(Right) Focus group meeting on benefit-sharingunder the Low Carbon City Project (LCCP)The Department of Highways received a Carbon Neutral Event Certificate from the Thailand Greenhouse Gas Management Organization (TGO).The Department of Highways delivered a presentation on the topic “Enhancing Acceptance and Confidence in Thailand’s Environmental Impact Assessment System,” organized by the Office of Natural Resources and Environmental Policy and Planning.Environmental Partnership for Climate Change MitigationCapacity Building and Knowledge Sharing for Environmental SustainabilityAs Thailand’s main transport authority, the Department of Highways has advanced national climate change initiatives for greenhouse gas mitigation and climate adaptation under the United Nations Framework Convention on Climate Change (UNFCCC). In this regard, the department has participated in the following workshops, focus group meetings, and training programs:The Department of Highways has prioritized personnel capacity building, knowledge development, and inter-agency collaboration to enhance sustainable environmental management in all highway operational domains. In this regard, the department has organized and participated in environmentally friendly initiatives; staff have made technical presentations and participated in training programs, as described hereunder:1. Organized the “DOH KM Festival 2025” under the theme “DOH Innovation: Driving Thailand Toward Sustainability.” The event was conducted in line with comprehensive environmentally responsible principles, integrating greenhouse gas reduction and carbon offset measures while promoting environmental awareness among participants. The department will continue its progress towards achieving carbon neutrality by 2050 within the purview of sustainable transport development.2. Participated as speakers on environmental topics.94 Annual Report 2025 Department of Highways

Output 1: Highway Network DevelopmentOutput 2: Maintenance and Management of the Highway Network and BridgesIntegrated Transport and Logistics Development Plan1) Administrative and support activities for highway development1.1 Construction of residential buildings and associated structures1.2 Construction of office buildings and associated structures1.3 Renovation of residential buildings and associated structures1.4 Renovation of office buildings and associated structures1.5 Construction of office and residential buildings, along with associated structures,for the Ranong Highway District (budget commitment: 2023-2025)1.6 Construction of the Road Human Resources Development Training Center(Southern Region) (budget commitment: 2024-2026)1.7 Construction of five-storey residential buildings (40 residential units) on the Rama VIRoad side (budget commitment: 2024-2026)1) Highway maintenance1.1 Routine maintenance1.2 Periodic maintenance1.3 Special maintenance and rehabilitation1.4 Sustainable restoration of disaster damage1.5 Improvement of low volume roads2) Emergency restoration of disaster damage3) Bridge and structure maintenance• Major highway network rehabilitation• Improvement of drainage efficiency on highways Strategic plan and other expenditures (consultancy projects) 523.0943 million baht192.2000 million baht68.4250 million baht33.5370 million baht35.3100 million baht88.4973 million baht70.1250 million baht23.1000 million baht26,144.0697 million baht7,136.2800 million baht6,990.9765 million baht9,251.7703 million baht2,407.9060 million baht357.1369 million baht200.0000 million baht680.3479 million baht4,603.7630 million baht545.4800 million baht91.4472 million bahtHighway MaintenanceFor the fiscal year 2025, the Department of Highwaysreceived a total budget of 32,788.2021 million baht for highway maintenance. The budget was disaggregated into: basic planning for enhancing competitiveness, which consisted of administrative and support activities for highway development (523.0943 million baht); highway maintenance activities (26,144.0697 million baht); bridge and structure maintenance activities (680.3479 million baht); emergency restoration of disaster damage (200 million baht); consultancy projects (91.4472 million baht); integrated transport and logistics development planning, which consisted of major highway network rehabilitation projects (4,603.7630 million baht); and improvement of drainage efficiency on highways (545.4800 million baht). A budget breakdown is given hereunder:Annual Report 2025 Department of Highways 95

The Department of Highways conducted the followingmaintenance activities and projects in 2025:1. Administrative and Support Activities for Highway DevelopmentThis category encompassed the construction and renovation of departmental office buildings and residential facilities. Many of these structures, having aged over time, required maintenance to ensure continued functionality. A total of 704 facilities were addressed, including office buildings, residential buildings, and related structures across 18 highway offices, 104 highway district offices, and 581 highway depots.2. Highway Maintenance Activities Routine maintenance involves regular upkeep, minor repairs, and cleaning to ensure highways, bridges, and highway assets remain in optimal condition and to extend their service lives, thereby providing convenience, cleanliness, and orderliness, and, in particular, improved safety for road users. Minor modifications or upgrades are carried out as needed, as well as temporary measures to prevent further deterioration pending maintenance or rehabilitation works.Routine maintenance addresses:1. Pavements and shoulders2. Sidewalks, connection roads, medians, and bicycle lanes, as well as their repair 3. Drainage systems, bridges, and structures 4. Traffic and safety devices5. Landscaping6. Supplementary activities for enhancing highway maintenance efficiencyPeriodic maintenance is a preventive highway maintenance activity that must be carried out to extend service life and strengthen the highway to support futuretraffic volumes. It includes concrete pavement jointreplacement, unpaved surface reinforcement, asphalt surface reinforcement, asphalt seal coating, and paraslurry seal coating.Periodic maintenance methods include:1. Asphalt seal coating2. Asphalt overlay3. Replacement of joint sealantsHighway No. 101 (Pua - Pang Hok)at Sta. 440+000 - Sta. 440+025Highway No. 101 (Chang Phueak Intersection - Pua)at Sta. 372+500 - Sta. 372+800Highway No. 1149 (Huai Khrai - Huai Nam Rin), Section 0100, at Sta. 0+030 - Sta. 0+050Highway No. 1 (Phan - Rong Khun), Section 1401,at Sta. 890+370 - Sta. 919+034Highway No. 1090 (Pong Sanuk - Nan)at Sta. 131+000 - Sta. 132+00096 Annual Report 2025 Department of Highways

Special maintenance and rehabilitationSpecial maintenance involves highway repairs for damage the extent of which exceeds the scope ofregular maintenance work. In particular, routes that do not receive timely maintenance may deteriorate rapidly and require special maintenance interventions. Special maintenance repair methods include:1. Surface leveling2. Major repair of asphalt pavement3. Asphalt hot mix recycling4. Major repair of concrete pavement5. Major repair of side slopes and back slopes6. Major repair of bridge and highway structuresRehabilitation involves repairing severely damaged highways that cannot be addressed through special maintenance.Rehabilitation methods include:1. Asphalt pavement rehabilitation2. Concrete pavement rehabilitationSustainable restoration of disaster damageinvolves restoring highways or government property damaged by disasters such as floods, windstorms, and landslides. Restoration is carried out as appropriate to sustainably restore highways to safe and functional conditions. In 2025, Thailand experienced prolonged and widespread flooding from May to October due to Tropical Storms Wipha and Bualoi; the central, northern,northeastern, and southern regions were the mostseverely affected. Improvement of low volume roads involvesupgrading two-lane secondary highway networks (four-digit national highways) that carry fewer than 2,000 vehicles per day. These routes are typically located at the periphery of the network, lack continuity with main corridors, and serve remote areas. Therefore, efforts are made to enhance connectivity among communities and to provide equitable access to essential public services, including hospitals, schools, and government offices, all within the scope of ensuring safe, convenient, and efficient travel.Highway No. 3241 (Si Racha - Nong Kho Reservoir)at Sta. 10+600 - Sta. 12+130Highway No. 3191 (Nikhom Phatthana Intersection - Nong Pla Lai Reservoir) at Sta. 23+782 - Sta. 24+470Highway No. 1081 (Bo Kluea - Chaloem Phra Kiat)at Sta. 117+700 - Sta 119+600Highway No. 1083 (Den Chat - Na Noi)at Sta. 68+675 - Sta. 72+000Annual Report 2025 Department of Highways 97

3. Maintenance of Bridges and StructuresThis activity involves the repair and maintenanceof bridges because of the increasing number ofstructural incidents that affect the transport network, generating significant economic and social impacts. Such incidents may be caused by overloading or age-related structural deterioration. In this context, to ensure safe and uninterrupted service, systematic maintenance and rehabilitation are required, including structural strengthening to accommodate current traffic volume.4. Emergency Restoration of DisasterDamageThis activity covers urgent measures to address disaster-related traffic disruptions, including flood prevention and mitigation and repairs to highways and the department’s assets damaged by floods,windstorms, landslides, and other unforeseen events, in order to promptly restore smooth traffic flow. In 2025, restoration works included reopening routes, returning them to normal conditions, and implementing proper preventive measures on vulnerable sections in line with established standards. More than 445 locations were addressed, with a total budget of 200 million baht.5. Rehabilitation of Major HighwayNetworksMajor highway networks serve as primarytransport corridors connecting regional routes,provincial clusters, and international links. These routes also connect key strategic and logistics hubs, including ports, airports, border checkpoints, industrial estates, and special economic zones. Due to high traffic volumes and substantial heavy truck traffic, the routes deterioraterapidly and require special maintenance with higher budget allocations than general highways. In response, the Department of Highways allocates regular funding for the rehabilitation and maintenance of major highwaynetworks to safeguard national transportation and boost sustainable economic and social development.6. Improvement of Drainage Efficiency on HighwaysThis work addresses drainage deficiencies in areas affected by flooding and recurrent inundation,primarily due to urban expansion and changes in land use along highway corridors. Prolonged rainfall has caused extended flooding in previously unaffected areas, disrupting traffic movement, logistics operationsand public travel, increasing accident risks, andaccelerating highway deterioration, thereby inducing higher maintenance costs. Drainage improvements in flood-prone areas are therefore required to enhance discharge capacity and mitigate impacts on thehighway network.Highway No. 1130 (Pa Sang - Kio Satai), Section 0100,at Sta. 40+645 - Sta. 40+715Highway No. 1150 (Khun Chae - Wiang Pa Pao),Section 0200, at Sta. 60+675 - Sta. 65+566Highway No. 1243 (Huai Phai - Hat Rai)at Sta. 77+050 - Sta. 77+12598 Annual Report 2025 Department of Highways