Traffic Signal Progression

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The City of Ames Traffic Department has improved the coordination of the traffic signal system throughout the City. Coordinating traffic signals involves connecting them so they work together to provide motorists with green lights as they progress down the street.

Q. How does Traffic Signal Progression help drivers?
A. Coordinated traffic signals provide the following benefits to Ames’ motorists:

  • Delay experienced by motorists waiting at signals is reduced.
  • The number of stops experienced by motorists is reduced.
  • Motorists are grouped in platoons traveling at equal speeds.
  • There are fewer rear-end accidents because motorists are stopped less often on major streets.
  • There are fewer right-angle accidents because there is less red light running.
  • There is less traffic cutting through neighborhoods to avoid signals.

Q. If the signals are coordinated, why are motorists stopped at red lights?
A. It is impossible to time the signals so that no driver gets a red light.

  • If you are hitting a number of lights on red, you may be driving too fast since the signals are timed for motorists traveling near the speed limit.
  • If signals are spaced closely together, it is difficult to achieve progression.
  • When traffic is very heavy, such as driving during rush hour, the signals are timed for the peak direction of travel. If you are traveling against the peak, you may hit more red lights.
  • If you turn onto a major street, you may hit a red light or two before you get into the "green band" and find yourself in synchronization with the timing plans.