Traffic Light Design - I

Posted by CS

Traffic light is a common infrastructure in normal city. Do you know the design of the traffic light is having HUGE impact to the traffic flow? I wonder if you notice when reach certain traffic light, the chances of having traffic jam is lower. But some junction caused higher traffic congestion.

You may think is because of the different traffic rate flow to the same direction or there is bottle neck of the whole traffic flow.

But have you ever think of the design of the traffic light is playing an important role? How important it is? There are 2 main factor... Sequence of traffic light and the frequency of traffic light switching.


Let me explain why... you will find it interesting.....

Some of the traffic light is having clock wise and anti clockwise switching sequence, Some of them not. U may wonder.. will it make any different? The answer is YES... Definitely YES.. but HOW?


Take a look at the picture below, this is the normal clockwise switching sequence. Do you see any issue?



Then try to look at this one...... Look at the red spot at the pic 2,3,4, Those are the places where the traffic is highly congested as the previous switching corner is giving ways the traffic to the same direction. SEE?



After corner 1 giving ways to traffic to flow into corner 3 and 4, then when switch to corner 2, the traffic flow into corner 4 and 1. Which mean, corner 4 will have congestion as the origin traffic from corner 1 still yet to release the congestion.

Same rules go for one after another one... This is a BAD design....

For a good design, the switching sequence should set in the way as show in below picture. This will give more time for one corner to release more traffic out from the congestion area.



Try to put a bit attention when u reach a cross road with traffic light and see if the traffic light is using clockwise, anti clockwise or use the methods B ping pong style? And you may confirm of the performance of the traffic light help to reduce traffic jammed.

If proof on my concept, can anyone give a call to MPPP feedback ?

Stay tune for part II, frequency of traffic light switching.. hihi

• at Thursday, December 06, 2007