Left Turn Traffic Signals

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There are two types of left turn signals, "protected" and "protected/ permissive," in operation at City intersections. Many drivers often ask questions and express confusion regarding the operation of the protected/permissive left turn signals.

PROTECTED LEFT TURN SIGNALSleft turn

Drivers have been accustomed to seeing left turn signals where there is initially a green arrow followed by an amber arrow followed by a red arrow. On the green arrow, drivers are given the right-of-way to complete left turns free of any other traffic conflicts. The amber arrow warns drivers that the left turn signal is ending. On the red arrow, left turns are not permitted. These types of left turn signals are called "protected" left turn signals. They can be helpful, but when there is no opposing traffic they can cause unnecessary delays.

PROTECTIVE/PERMISSIVE LEFT TURN SIGNALS

Over the last several years, a five-section left turn signal has been implemented at intersections in the City. Under this new arrangement, left turn signals provide the usual green arrow, which is usually followed by the yellow arrow. After the yellow arrow has terminated, motorists are faced with a solid green ball signal (no red arrow). During the display of the solid green ball, left turns can be made when there are adequate gaps in opposing traffic to complete left turns safely. This type of left turn phasing is designed to help minimize delays 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 during rush hours when traffic is heavy, but during off-peak hours, left turning vehicles are not delayed by a red arrow. Recently, the City has added the protected/ permissive phasing to the existing traffic signals at the intersections of Haskell Canyon Road/Grovepark Drive, Plum Canyon Road/Rodgers Drive, Avenue Crocker/Rye Canyon Road, and Bouquet Canyon Road/Espuella Drive.

ADVANTAGES OF PROTECTED/PERMISSIVE LEFT TURN SIGNALS

The advantages of this operation when compared to fully protected phasing only are:

  • Reduces delays, as left turn drivers may have an opportunity to make their left turns during the green interval.
  • Allows the use of shorter cycle length in coordinated systems by reducing the time of the fully protected green interval for the left turn movement.
  • Less chance of disturbing traffic in adjacent lane as left turn queues are less likely to exceed the length of the left turn lane.

IF YOU HAVE ANY QUESTIONS, REQUESTS, OR SUGGESTIONS CONCERNING TRAFFIC SAFETY MATTERS, PLEASE CONTACT THE TRAFFIC ENGINEERING DIVISION AT (661) 255-4942