Traffic Signals

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The Manual on Uniform Traffic Control Devices (MUTCD) governs the use of traffic signals, street striping, roadside signs and work zone barricades nationwide. Some of the newest changes are the inclusion of pedestrian countdown times and the standardization of flashing left arrows.

The city uses a traffic signal model program to help time traffic signals. Traffic counts consisting of tube counts taken for 24 hours and turning movement counts taken during 3 times of day are input into Synchro, a modeling program. Signal analysts and engineers then work to balance vehicle progression, favoring north and east in the morning and south and west in the evening, for optimal traffic flow.

In general, the goal is to provide 3 out of 4 signals green for commute traffic. The city traffic signal system is continuously updated, and one-third of the city is re-timed each year. Signal analysts at the Traffic Management Center also handle special issues, incidents and events to keep traffic running smoothly in Chandler. Most signals in the city operate on a 94-second cycle.

The city uses electronic vehicle detection for traffic signals as opposed to magnetic induction from loops embedded in the roadway. The detection system notifies the traffic signal controller that a vehicle is waiting for a specific signal indication.

Protected and permitted left turns in a designated left-turn bay and protected double-left turns are all programmed for minimum and maximum times, depending on traffic demand. The continued presence of vehicles in the detection area will extend a signal indication.

At right-turn bays, the signal indication is delayed to allow the vehicle to make a right on red, where permitted, before it will turn green for the approaching traffic. If, after 5 seconds, the vehicle is still at the signal, the controller will get "a call" to go green for that direction.

The pedestrian detection system is an important part of the city's signal system. Pedestrians must push the button to indicate their presence, which, in turn, alerts the signal controller to extend the traffic signal cycle to accommodate the pedestrian.

When a pedestrian approaches an intersection, they must push the pedestrian button to indicate their presence. The pushbutton then alerts the signal controller to extend the traffic signal cycle to accommodate the pedestrian. The white pedestrian symbol means it is OK to start across the street. The flashing hand means the pedestrian should not start across as time is not sufficient to cross the entire intersection. The City has approximately 30 intersections with countdown times that actually display the remaining time to safely cross the street.

A grant from the Maricopa Association of Governments and the Arizona Department of Transportation will allow the City to add more than 70 new countdown timers at intersections. At most intersections, approximately 25 seconds are allocated for a pedestrian to cross. The actual time varies depending upon the width of the intersection, but pedestrians need to push the button to get the cycle extended for safe crossing.

Chandler is installing flashing yellow left-turn arrows to indicate permitted left turns. The left turn must still yield to oncoming traffic, but instead of a green light, the signal displays a flashing yellow arrow.