Question

Often, traffic lights of a series of intersections are timed so that if you travel at a certain constant speed, you can avoid all the red lights throughout. Discuss how the timings of the different coloured lights are determined, considering that the distance between them varies from one crossing to the next?

Answer 1

1. The timings of the different colored lights are determined based on the average speed of the driver.
2. In this problem, let us assume that a person is traveling at a constant speed and the distance between different traffic lights is different.
3. Using the formula, $Time=\frac{distancebetweentwotrafficlights}{speedoftraveller}$, the time can be calculated after which the light of the next traffic light will turn green.
4. For example, the allowable speed is $20m{s}^{-1}$ and the distance between the first two traffic lights is $4000m$, then $time=\frac{4000}{20}=200s=3min20s$.
5. It means that after $3min20s$ the signal on the second traffic signal will turn green. Similarly, the timings of lights of other crossings can be found.

Thus, a person traveling can avoid all the red lights if a constant speed is maintained depending upon the distance between two lights and the allowable limit of speed in that area.