Petaluma Going Yellow for Left Turns

left turn signal

Yesterday the Press Democrat reported on Petaluma replacing the "left on green" signals with flashing yellow lights

The city will replace all or some of the protected-permissive signals at 26 intersections throughout town, while allowing a few to remain as is.

Some will include a signal new to California and what may be a first for Sonoma County — the flashing yellow left-turn arrow.

Petaluma Boulevard North at Magnolia Avenue/Payran Street had a “higher than expected collision experience involving left-turning vehicles,” Zimmer said.

In all four directions, the protected-permissive signals will be replaced with protected left-turn phasing, meaning left-turn drivers will see a progression of green, yellow and red arrows.

Then, once the intersection is cleared, a flashing yellow arrow will light, alerting drivers that they may proceed with caution with a left turn when oncoming traffic is clear.

The 2009 MUTCD includes languange about flahsing yellows for left turns (4D.17-4D.20). The topic is also discussed in NCHRP Report 493: Evaluation of Traffic Signal Displays for Protected/Permissive Left-Turn Control. While Petaluma is the first city in California to implement this sort of signal, it has been catching on across the nation. Next year, two different research projects investigating the impacts of flashing yellows on protected left turns should be completed. One is Evaluation of Flashing Yellow Arrows (FYA) for Protected/Permissive Left Turn (PPLT) Control from Bradley University for the Illinois DOT. The other is Field Study of Driver Behavior at Flashing Yellow Arrow vs Green Ball Permitted Left-Turn Indications by CTS of the University of Minnesota for the ITS JPO of RITA

 (Hat tip to @thedotreport)