Protected Left Turn Arrows
Protected left turn signals include a red arrow along with the normal green and amber arrow. They allow left turning drivers to proceed only on the green arrow. This turning method is very inefficient and generally not used in Tucson. Adding inefficiencies to signal timing reduces overall capacity and increases congestion. With increased congestion comes the potential for an increase in certain types of accidents.
Permitted/Protected Left Turn Arrows
This is the most common turning method used in Tucson at locations having left turn arrows. During the permitted "green ball" part of the cycle, vehicles are allowed to turn when there are adequate gaps in opposing traffic.
This type of left turn phasing is designed to help minimize delay by eliminating the need for the red arrow and allowing vehicles to turn on the green ball after opposing traffic has cleared. By not having the red arrow, motorists do not have to sit and wait to turn left even when there is no opposing traffic, a situation that often occurs during periods of low traffic volumes. The signal still provides a green left turn arrow for those not able to turn during the permitted phase.
Leading vs. Lagging Arrows
The City exclusively used leading left turn arrows until the early 1980's. In 1984 we experimented with lagging left turn arrows on 22nd Street between Park and Wilmot. Studies done before and after the change comparing the two methods showed that during much of the day lagging arrows were superior. They allowed improved progression, reduced delay and lowered overall intersection accidents.
Leading arrows do have some advantage over lagging arrows in certain circumstances. That's why there are still a few in the city. They generally are used at intersections where one direction of traffic requires the installation of an arrow while the opposing direction does not.
Leading Yellow Flashing Arrows
The City of Tucson Department of Transportation (TDOT) has introduced flashing yellow arrows at some of its traffic signals throughout the City. With this change, many motorists have contacted TDOT with questions. Below are some of the questions TDOT has received, followed by answers.
What does the flashing yellow arrow indicate?
Turn with caution. Bicyclists and motorists may turn in the direction of the flashing yellow arrow without stopping if there is a safe gap in oncoming traffic, while yielding to pedestrians and bicyclists.
Why did the City add the flashing yellow arrow?
Traffic signals with the new flashing yellow arrows are safer for pedestrians. When a pedestrian pushes the “Walk” button, the left turn arrow will turn red for motorists, while the “Walk”and pedestrian countdown display is on. Pedestrians can cross busy streets safely because left turning vehicles are prohibited from turning on a red arrow.
Will a traffic signal ever change directly from a flashing yellow arrow to a red arrow?
No. There will always be a solid yellow arrow before a red arrow.
Am I allowed to stop when the yellow arrow is flashing?
Yes. The flashing yellow arrow means proceed with caution. If it isn’t safe to turn, stop and wait until it is safe to complete your turn.
I’ve seen a flashing yellow arrow change to a green arrow. Are they supposed to do that?
Yes. The change from a flashing yellow arrow to a green arrow means that turning traffic has the right of way.
Can a green arrow change to a flashing yellow arrow?
Yes. A green arrow changing to a flashing yellow arrow means that turning traffic no longer has the right of way and must yield to bicycles, pedestrians, and other vehicles before turning.
What does it mean when the traffic signal is red but the left turn arrow is flashing yellow?
It means that oncoming traffic has the right of way on a green light. Vehicles intending to go straight through the intersection facing a red light must stop and not proceed unless allowed to make a right turn on red. Bicyclists and drivers turning left may carefully proceed through the intersection after yielding to any approaching traffic.
If you would like more information about flashing yellow arrows, call the Tucson Department of Transportation Traffic Engineering Division at (520) 791-4371.