The traffic signal master assigns different cycle lengths to the signals during the day. The length is determined by traffic demand. Cycle lengths vary from 50 to 140 seconds when signals are coordinated. City traffic engineers and technicians are constantly upgrading the City's system by monitoring traffic volumes on street and turning movements at busy intersections. This information is used to time the signals and help traffic flow with less delay.
Many drivers ask why they have to wait so long for a signal to change.
To allow the coordination of the arterial, the side street must wait until the main traffic movement on the arterial has gone through the intersection. It is possible that the arterial traffic can't be seen immediately, but will soon be passing through the intersection.