Traffic Light timing length
The length of amber lights can differ, for example in many places the length of an amber light is usually 5 seconds, but elsewhere it may be as little as 3 seconds considerably reducing the time the driver has to react. It is typical for these times to vary according to the set speed limit, with longer times given for higher limits.
The time from when a red light is displayed and when a cross street is given a green light is usually based on the physical size of the intersection itself; this intervening period is called the all-red time. A typical all-red time is 2 sec to allow cars to clear the intersection. In a wider intersection, such as 4 lane road or highway intersection, the all-red time may be as much as 4 seconds, allowing drivers who could not stop at the amber light enough time to clear the intersection without causing a collision.