The majority of results from this process will be somewhere near the average. This is because there are lots of different ways to be near the average.

For example:

• all the traffic lights delaying by about 50% of their red time, or
• the first and last traffic light delay by 100% of their red time and the others with no delay, or
• one traffic light delays by 100% of its red time and the other three delay by 33%.

There are lots of other combinations which add up to about the average delay.

On the other hand there is only one way to get the fastest result - all lights at green - and only one way to get the slowest result - arrive at every traffic light just as it turns red.

NOTE: This is not meant to be a rigorous description of the distribution of delays by traffic lights. I have found that this explanation works for my purpose.

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