Research helps improve safety for those who walk and roll

Flashing yellow arrow indication for right turns will be an option at intersections

It might just get a little safer out there for those who walk, ride and roll, based on some changes coming with the Oregon Department of Transportation’s 2022 Signal Design Manual. It’s thanks to work coming out of ODOT’s Research Section, with help from teams at Oregon State University and Portland State University.

Katie Johnson, P.E., Traffic Signal QC engineer in ODOT’s Traffic-Roadway Section, described the change as one that will result in better decisions by drivers.

“The research showed that use of a right turn flashing yellow arrow at an intersection improved the yielding behavior of drivers to pedestrians when compared against the standard circular green ball,” Johnson said. “Flashing yellow arrow signal indications are quickly understood by drivers – for example, flashing yellow has always meant use caution and be aware of conflicts: yield to oncoming traffic or pedestrians.”

Dissecting the problem

It’s true that drivers generally understand the meaning of flashing yellow arrows for left-turn situations, but research was needed to examine driver responses to the use of flashing yellow arrows for right turns.

Busy urban intersections are often scenes of conflict: distractions can draw driver attention and hinder proper yielding to nearby bikes and pedestrians. In fact, “turning vehicles” are the most common cause of collisions for pedestrians and bicyclists. When it involves a person bicycling, it’s called a right-hook crash. This topic has been the focus of several research efforts and now – with the latest one (Improved Efficiency of Protected/Permitted Right Turns in Oregon (SPR 789)) – it’s clear that using a flashing yellow arrow for right turns can have a positive impact.

That’s why they’ll be added to the 2022 Signal Design Manual, setting them on the path to become the norm for intersections where protected/permitted right turn phasing is the appropriate solution.

“For reference, there are three types of right turn phasing: permissive only, protected/permitted, and protected only. Permissive only right turns will still use a green circular ball indication (due to lane use limitations and hardware limitations in the controller cabinet) and protected only right turns will still use a green arrow,” Johnson said. The graphics here demonstrate these concepts.

Another tool in the engineer’s toolbox

“If you had not heard, we got some good news last week that I think you will enjoy,” Oregon State University Professor David Hurwitz, who collaborated on the research with Portland State University Professor Chris Monsere, wrote in an email to the team. “The signal head configurations recommended by Our Research project SPR 789 have been incorporated into an ODOT standard for Flashing Yellow Right Turn Arrows in the 2022 Signal Design Manual.”

In the Portland metro area, ODOT Region 1 Central Signal Manager Patrick Mahedy is looking forward to more flexibility in intersection signal design.

“For pedestrian safety, this allows for a larger spectrum of outcomes,” said Mahedy. “Before if there was a right turn lane, the only options were to either display a green ball simultaneous with the pedestrian walk and flashing don’t walk intervals, or display a red arrow for the duration of the pedestrian walk and flashing don’t walk intervals. Now we have the flexibility to display a red arrow during the walk, allowing pedestrians to enter the roadway before right turning vehicles, and the more intuitive flashing yellow arrow during the flashing don’t walk, indicating that turning drivers must yield to those pedestrians.”

Improving safety throughout the transportation system is a critical part of ODOT’s Strategic Action Plan, a document that guides the agency’s work around three priorities: equity, a modern transportation system and reliable and sufficient funding.

Permissive signal

Protected Signal

Protect Permit Signal

The easier to understand, the better

By now, most drivers know what a flashing yellow left turn signal means, but it took years to become the standard – and still may be fairly new in some parts of the country. The bottom line is, the easier a signal or direction is to understand, the faster we can respond correctly.

“Traffic control devices need to be simple, uniform and intuitive,” ODOT’s Johnson said. “If they aren’t, drivers will require much more time to process the correct action to take or won’t respond correctly, likely resulting in increased near-misses and crashes.”

Professor Hurwitz said one of the more significant findings from the research was, in fact, that people (drivers) understand the flashing yellow turn arrow concept.

“The comprehension rates were so high, and the correct responses so positive, we don’t believe that we’ll need supplemental signage to achieve high comprehension rates,” he said.

So get ready: a flashing yellow right turn arrow may be coming to an intersection near you – along with improved safety for those who walk and roll.