Signal coordination is a signal timing strategy used by traffic engineers to improve operations for vehicles primarily traveling long distances along a corridor. Signal coordination works by giving a series of signals the same cycle length and then synchronizing them to give vehicles a “green wave” to reduce the number of stops drivers make and the amount of delay they experience.
Coordination is a great method for moving people through a corridor where most of the people are moving from end to end, for example between cities or along a one-way major commuter route through a city. The signals in a coordinated system are timed based on a design speed, so if a driver is speeding, for example, they may not catch the “green wave” and will end up stopping at one or more signals.
In order to coordinate traffic signals, a traffic engineer must pick a cycle length that accommodates the most critical intersection in a corridor, which often forces all intersections along the corridor to have a long cycle length. For most traffic signals in the United States, one minute to two-minute cycle lengths are most common. In Florida cycle lengths of three, four, five or even six minutes are common. For vehicles traveling end to end along the corridor this is not a problem, but for anyone trying to make a turn or enter the corridor from a cross-street, this can create a long delay. Long cycle lengths also create long queues, or lines of cars, that can block intersections and driveways, or even block the through movements on a corridor.
Coordinating a corridor with long cycle lengths can be dangerous for pedestrians, who often cross against the traffic signal if the cycle is too long. Long cycle lengths also encourage drivers to speed., Crashes at high speeds are more likely to be severe or fatal.
Along most corridors within cities, travelers are going to a destination or several destinations along a corridor, for example to travel from work to a restaurant for lunch, or to go shopping or run errands. In this scenario, the traffic signals may be timed to give the drivers the ability to move around the area from one destination to another, rather than through it. This means drivers will stop at the signals and everyone must “wait their turn.” When the cycle length is shorter, the time to “wait your turn” is shorter.