COURSE HANDOUT HOW DO TRAFFIC LIGHT SIGNALS WORK???
D E FI N I T I O N O F J U N C T I O N A road junction is where two or more roads either meet or cross at grade (they are at the same level) or different levels (interchange). Such a road junction may also be called a crossroads. Red light:- During which vehicles in a particular leg of an intersection halt Signal controlled intersect ions are applicable to very high traffic volume of 8,000 veh/hour or more provided that the necessary number of approach lanes are present and that there is no interference from other nearby junctions. Manual: Arahan Teknik Jalan 11/87: A guide to the design of at-grade junctions Arahan Teknik Jalan 13/87: A guide to the design of traffic signals Generally, any traffic signals consist of: 1. 2.Amber/ Yellow light:- During which vehicle will turn on ignition and start to accelerate 3.Green light:- Vehicle will move out of intersection Traffic signals, also known as traffic lights, are devices used to manage the flow of traffic at intersections and other roadway locations. They typically use a combination of red, yellow, and green lights to indicate when vehicles and pedestrians should stop, proceed with caution, or proceed through the intersection. There are several types of traffic signals, including: Fixed-time signals: These signals use a fixed timing sequence, with each light color displayed for a predetermined amount of time. Fixed-time signals are typically used in areas with consistent traffic patterns. Actuated signals: These signals use sensors to detect the presence of vehicles or pedestrians and adjust the signal timing accordingly. This allows for more efficient traffic flow and reduced wait times. T R A FFI C S I G N A L S
ADVANTAGE A D V A N T A G E S & D I S A D V A N T A G E S T R A FFI C S I G N A L S T R A FFI C S I G N A L S Provides a better movement of vehicles and secures the safety of pedestrians Reduce the number of conflicts at a junction Increases the efficiency in controlling vehicles’ movements at junction areas Allows drivers to be more confident as they are aware of their rights to move. DISADVANTAGE During non-peak hours, traffic signals increases time of unnecessary delays at junctions. Increases the possibility of road accidents when drivers disobeys stopping at red lights Technical errors which cause traffic light malfunction will cause immediate standstill Requires regular maintenance
T R A FFI C S I G N A L S P H A S E S A Phase is that part of a cycle where one or more streams of traffic is (are) allowed to occupy the road simultaneously Consider diagram. It shows intersection with four legs. Let me call each leg by a name A,B,C and D. In a two-phase signal, There will be two phases. i.e., 1st phase: Traffic streams from A and C are allowed to cross intersection while traffic streams from B and D are stopped. 2nd phase: Traffic streams from B and D are allowed to cross intersection while traffic streams from A and C are stopped Two-phase traffic lights are a type of traffic signal that consists of two distinct phases or cycles of operation. In the first phase, one direction of traffic is allowed to proceed, while the other direction is required to stop. In the second phase, the roles are reversed, allowing traffic from the other direction to proceed while the first direction stops. 2 - P H A S E C Y C L E
Two-phase traffic lights are commonly used in situations where the traffic flow is relatively balanced between the two directions, and where there is no need for a dedicated turn phase or pedestrian phase. They are often used in smaller intersections or on less busy roads where there is not enough traffic to justify the use of more complex signal systems. Overall, the use of two-phase traffic lights can help to improve traffic flow and reduce congestion, while also ensuring the safety of drivers and pedestrians.A Phase is that part of a cycle where one or more streams of traffic is (are) allowed to occupy the road simultaneously 3 - P H A S E C Y C L E Three-phase traffic lights: These signals have three distinct phases, with a dedicated phase for turning traffic. They are often used in larger intersections or on busy roads where the traffic flow is more complex. There are 3 options diagram movement for 3 phase. onsider diagram.
OPTION 1: MAJOR LANE W-E OPTION 2: MAJOR LANE W-E OPTION 2: MAJOR LANE W-E
Three-phase traffic lights offer several advantages over two-phase traffic lights, including: 1.Improved traffic flow: Three-phase traffic lights allow for more complex traffic patterns and better coordination of traffic flow. By controlling traffic in three directions, they can better accommodate the varying traffic volumes and congestion levels at an intersection. 2.Reduced delays: With better traffic flow management, three-phase traffic lights can help reduce delays and waiting times for drivers. 3.Increased safety: Three-phase traffic lights can reduce the risk of accidents at intersections by providing more time for pedestrians to cross safely and allowing drivers to make turns without conflicting with oncoming traffic. 4.Enhanced flexibility: Three-phase traffic lights can be programmed to adjust to changing traffic conditions, such as rush hour or special events, which can help to further optimize traffic flow and reduce delays. Overall, three-phase traffic lights are a more efficient and effective solution for managing traffic flow and improving safety at intersections, especially in areas with higher traffic volumes. 4 - P H A S E C Y C L E Four-phase traffic signals, also known as four-way traffic signals, are a type of traffic signal that controls traffic flow at an intersection in four directions. They typically use red, green, and yellow lights to indicate when traffic should stop, proceed with caution, or proceed through the intersection. Four-phase traffic signals offer greater flexibility and efficiency than two-phase or three-phase traffic signals because they can better accommodate the varying traffic volumes and congestion levels at an intersection. They are commonly used at busy intersections with high traffic volumes and complex traffic patterns.
The four phases of a four-phase traffic signal are: North-South green: Traffic traveling in the north-south direction is allowed to proceed through the intersection while traffic in the other directions is stopped. North-South amber/yellow: Traffic traveling in the north-south direction is given a warning to stop while traffic in the other directions is still stopped.
East-West amber/yellow: Traffic traveling in the east-west direction is given a warning to stop while traffic in the other directions is still stopped. East-West green: Traffic traveling in the east-west direction is allowed to proceed through the intersection while traffic in the other directions is stopped.