• Traffic lights are signaling devices positioned at road intersections, pedestrian crossings are today used in almost every city of the world.• On December 10, 1868, the first traffic lights were installed outside the British houses of parliament in London, by the railway engineer J.P. Knight.• The modern electric traffic light is an American invention, policeman Lester Wire invented the first red-green electric traffic lights.• The first four-way, three-color traffic light was created by police officer William Potts in Detroit.
Traffic lights alternate the right of way accorded to road users by displaying lightsof a standard color (red, yellow/amber, and green) following a universal colorcode.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 to do so, prepare to stop short of the intersection, and• Illumination of the red signal prohibits any traffic from proceeding.• Usually, the red light contains some orange in its hue, and the green light contains some blue, for the benefit of people with red-green color blindness.
The closed-loop system consists of sixcomponents:• System detectors• Local control equipment• Controller-master communications• On-street master• Master-central communications and• Central computer.
Traffic Light Design• We figured out some possible States of the Traffic Light.• Next, we should think logically about how the Traffic Light should behave.• For now, we will try to keep it simple.• (Suppose these are infrequently used country roads.)
How should the Light behave? ALight A B Light B Car Sensors
Traffic Light Behavior IF A=1 AND B=0Light A Light B
Traffic Light Behavior Note: Clock beats every 4 sec. IF A=1 So Light is Yellow for AND B=0 4 sec.Light A Light B
Traffic Light Behavior IF A=1 AND B=0Light A Always Light B
Traffic Light Behavior IF A=1 AND B=0Light A Always IF A=0 AND B=1 Light B
Traffic Light Behavior IF A=1 AND B=0Light A Always Always IF A=0 AND B=1 Light B