1.0 Introduction
A traffic light system is an electronic device that assigns right of way at an intersection or crossing or street crossing by means of displaying the standard red, yellow and green colored indications. In addition, it works in conjunction with pedestrian displays to assign pedestrian crossing right of way. A traffic light, also known as a traffic signal, stop light, stop-and-go light is a signaling device positioned at intersection, pedestrian crossing or other location in order to indicate when it is safe to drive, ride, or walk using a universal colour code (and a precise sequence, for that are colours blind).
Nowadays, a red light meant traffic in all directions had to stop. A yellow light means crossing traffic would have to slow and a Green light would have to go or proceed.
There are different ways of controlling intersections. in the simplest cases the right-hand-rule or if the traffic is higher, a roundabout or the signal of a Police man can help steer the traffic. However, especially in big cities, in the complicated cases when the roads in the intersection have several lanes, the use of traffic lights cannot be avoided. An addition of issue arises when in the intersection not only roads but also railway tracks take part, what often occurs in suburban traffic situations. The most common way to handle this type of intersection is the conventional cyclic light control.
There are two parts that are involved in accomplishing this construction of an electronic traffic controller — the software part and the hardware part. The software deals with the programming aspect of the circuit that controls the hardware while the hardware deals with the physical aspect of the circuit (components).
1.1 Benefits of Traffic Controller
When properly used, traffic control signals are important devices for the control of vehicle in road they assign the right-of way to a choice of traffic movements and thereby deeply influence traffic flow. Traffic control signals that are properly designed, located, operated, and maintained will have one or more of the following advantages:
- Provide orderly movement of traffic.
- Minimized competing movement.
- Coordinated for continuous movement.
- Provider confidence by assigning right way.
Traffic control signals are often considered a cure for all traffic problems at intersections. This belief has led to traffic control signals being installed at many locations where they are needed, adversely affecting the safety and efficiency of vehicular, bicycle and justified by traffic and road way condition, can be ill-designed, ineffectively placed, improperly operated, or poorly maintained.
While traffic signals can help in locations where they are justified and installed properly, they also have disadvantages. There will always be some disadvantages even if the signal is justified. One of the disadvantages is that an electronic traffic controller does not obey emergency situations.
1.2 Types of Traffic Signal Components and Operation
Traffic signals have the following components or parts:
- Main display with red, yellow and green lights.
- Traffic signal cabinet containing the traffic signal controller.
- Inductive loops or sensor.
In many cities, traffic signals mainly operate in three modes:
(a) Fixed-Time Mode:
Under this mode, there are no detections for any approach, the continuously cycles regardless of actual traffic demand.
Pedestrian walk signals are automatic and will cycle concurrently with the vehicular signal indicator
(b) Semi — Activated Mode:
Under this mode, the detection system is presented only on a minor cross street. When detection is activated, the green light is on a minor cross street. When detection is activated, the green light on a major street is interrupted to allow the minor street traffic and pedestrian to safety enter the intersection.
Pedestrian walks signals for crossing a minor street are not. Pedestrian crossing a major street must push the “pedestrian push button” to get the walk signals.
(c) Actuated Mode:
Under this mode, there are electronics for all approaches. The traffic signal set to provide the green light “On — demand” or only in the presence of vehicles.
This material contains electrical diagrams, circuits, illustrations and more (Very detailed).
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