Signals

Traffic signals help the movement of motor vehicle and bicycle traffic, and provide safe street crossings for pedestrians.


Traffic Signals

There are three types of traffic signals.

  • Pre-timed:  A pre-timed signal operates on a pre-determined schedule, regardless of how many cars are present at the intersection. Often, these signals are timed in coordination with other signals along a roadway. Most signals in Downtown are pre-timed. A pedestrian push button is not necessary at these signals because the "Walk" signal occurs when the green light appears. These signals do not have detection loops for bicycles or vehicles, because the green light is programmed to occur on a pre-determined schedule.
  • Fully Actuated:  A "fully actuated" signal reacts to the presence of a vehicle through detection loops in the pavement.  A bicycle that is in the center of the lane and behind the stop bar will trigger the signal just as a car would. Pedestrians who have pressed the pedestrian button also trigger these signals.
  • Semi-Actuated: Semi-actuated means that in an intersection of two roads, one roadway in the intersection is timed and one is actuated. Typically the lower volume or side street is activated.

All three types of signals can be either in "coordination" or "floating" mode. If a signal is in coordination, it means its operation is timed in coordination with other signals up and down the roadway. If a signal is floating, it means the signal reacts to the presence of cars, independent from other signals, not on a pre-timed schedule.

Pedestrian Signals

 

The length of time a pedestrian signal is displayed is based on the width of the roadway and the amount of green time in the signal. The "Don't Walk" time is determined by the width of the roadway, then the solid "Walk" time is added based on the length of the green in the pre-timed signal.  In fully actuated or semi-actuated signals, the "Walk" time is programmed typically to be 5 seconds, followed by the appropriate amount of "Don't Walk" time.

 

At pre-timed, fully actuated and semi-actuated signals, the "Walk" signal typically appears when the signal turns green. However, at a coordinated signal, if the signal is at a point in the cycle when there is not enough time to provide the required "Walk" and "Don't Walk" then the "Walk" signal is not provided until the next cycle.

 

Flash Mode

 

When traffic volumes are low, some signals are put in a flash mode. Signals flash yellow or red in flash mode; the predominant movement in an intersection flashes yellow signaling to proceed with caution, while the cross street flashes red, meaning stop before proceeding. Flash mode is used to reduce delays when lack of detectors does not allow fully-actuated operation. Where flash mode is used, it starts at 11:00 p.m. on weekdays and at 2:00 a.m. on Saturday and Sunday—always ending at 7:00 a.m.
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