Type of traffic signals Ppt

by, traffic Engineering book

1. TYPES OF TRAFFIC SIGNALS PREPARED BY:- RATHOD JAYDEEP ( 166250306546 ) 1

2. TYPES OF TRAFFIC SIGNALS 2 (A) Traffic control signals (1) Fixed-time signals (2) Vehicle Actuated Signals (3) Manually operated signals (B) Pedestrian signals (C) Special traffic signals

3. Typical traffic signal Traffic lights alternate the right of way accorded to road users by displaying lights of a standard color (red, yellow/amber, and green) following a universal color code. In the typical sequence of color phases: Illumination of the green light allows traffic to proceed in the direction denoted , Illumination of the yellow light denoting, if safe do so, prepare to stop short of the intersect and Illumination of the red signal prohibits any traffic from proceeding . Usually, the red light contains some orange in hue, and the green light contains some blue, the benefit of people with red-green color blindness. 3

4. (1) Fixed-time signals 4 These signals are set to repeat regularly in fixed cycle. Cycle regulates yellow, red and green lights in a fixed way Generally , duration of green and red light are same Time duration of light is dependent on traffic flow, traffic flow should be minimum.

5. (2) Vehicle Actuated Signals Vehicle-Actuated Signals require actuation by a vehicle on one or more Re approaches in order for certain phases or traffic movements to be serviced. They are equipped with detectors and the necessary control logic to respond to the demands placed on them. Vehicle-actuated control uses information on current demands and operations, obtained from detectors within the intersection, to alter one or more aspects of the signal timing on a cycle by-cycle basis. 5

6. Disadvantages 6 Type Disadvantages Fixed time Signals *Inflexible *Cause Avoidable delay Vehicle-Actuated signals * Require Costly equipment such as detectors Semi Actuated Signals * High traffic accidents at times of light traffic

7. 7 Advantages Type Advantages Fixed time Signals *Simple Construction and *Inexpensive Vehicle-Actuated signals * Flexible to adjust accord to traffic demand *Delay is minimized to attain maximum capacity Semi Actuated Signals * Useful for junctions of a low traffic volume

8. Pedestrian signals 8

9. Green arrow signal You may proceed in the direction of the green arrow. 9

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