Traffic Q&A: a blinking yellow arrow for making left turns
Last Tuesday, Steven V. Hatcher was driving west on Idaho 44, State Street, when his van was struck by an SUV turning left on a flashing yellow arrow onto Eagle Road. Hatcher’s van rolled and was pinned to a traffic pole, killing him.
Since 2016, Eagle police have expressed concern to state and county highway officials about flashing yellow arrows at intersections like the one where Hatcher died.
That year, the Ada County Highway District and the Idaho Transportation Department replaced “protected” left-hand turn signals — which allow a driver to turn left only when oncoming traffic is stopped — with “permissive” flashing yellow arrows, which allow drivers to make a left turn in the face of oncoming traffic after they yield.
“The blinking arrows turned on in early 2016, and we began to see a spike in crashes,” Eagle Police Chief Patrick Calley told the Idaho Statesman.
Between 2016 and 2017, ACHD engineers counted 26 crashes during left-turns at intersections with the flashing yellow arrow on State between Linder and Horseshoe Bend roads, Traffic Engineering Supervisor Ross Oyen said. Since the start of 2017, ACHD has received 11 police reports of left-turn crashes at the intersection of State Street and Eagle Road, not including the crash that killed Hatcher.
But Ada County Sheriff Office spokesman Patrick Orr suspects the number of crashes related to these intersections is higher.
Between April 2016, when the lights were installed, and May 2019, Ada County sheriff’s deputies have investigated 302 crashes on State Street between Idaho 16 and Idaho 55 at intersections with flashing yellow arrows. Four of them were fatal.
Of the 302 crashes, sheriff deputies attributed 88 to inattention, 38 to failure to yield and 19 to failure to obey the signal.
“We can’t say from our data exactly what the cause is, but inattention, failure to yield — those are all factors in left-hand turn crashes,” Orr said.
An Eagle Police post on Facebook about Hatcher’s death sparked debate over whether drivers or design engineers were to blame. Some called on transportation officials to re-evaluate the safety of intersections with flashing yellow arrows, which are popular with drivers because they reduce delays.
“The flashing yellows tend to incentive the driver to shoot a gap or make a turn quickly when the light turns red,” Don Kostelec, a Boise transportation consultant and former ACHD employee, said in a phone interview.
Change may be coming.
Last month, ACHD Executive Director Bruce Wong proposed that the agency spend $1 million to improve safety at intersections with flashing yellow arrows. Among the changes, Wong said ACHD would turn off the flashing yellows on roads with speeds over 45 miles per hour during peak hours, when traffic volumes are high and drivers have few opportunities to yield.
Wong’s proposal requires approval by ITD, which gives the final stamp on signal timing changes to state highways, including Idaho 44/State Street.
Already, the agencies say they will change one intersection: ITD and ACHD agreed on Wednesday to disable the eastbound flashing yellow arrow at the intersection where Hatcher died, ITD spokesman Jake Melder said.
If system-wide changes are made as Wong suggested, the move would reverse ACHD and ITD’s previous push for the yellow arrows to be installed throughout the county, despite initial caution in implementing them at high-speed intersections.
Making left-turns safer
Left turns are one of the most dangerous driving maneuvers, according to the Federal Highway Administration’s Office of Safety. About a quarter of all crashes at intersections occur during left turns.
Drivers turning left typically encounter one of two signals — the protected ones, which stop oncoming traffic so you can turn safely, and the permissive ones, which tell drivers to yield and let them decide when it’s safe to turn left.
Nearly a decade ago, ACHD realized the protected left turn signals were causing a safety problem of their own: Drivers felt they were waiting too long for the green arrow to turn and would run red lights during gaps in oncoming traffic.
So in 2010, ACHD began to install signals that authorize either protected or permissive left turns, depending on the time.
As a test, ACHD installed its first flashing-yellow signals on State Street in areas with speeds of 35 to 45 miles per hour, according to a 2015 report written by ACHD traffic engineer Tim Curns.
The results were encouraging: With the new flashing yellow arrows, the agency observed fewer crashes.
The Ada County Highway District Commission directed staff to install more flashing yellow arrows. But when it came to installing them on roads with speeds of over 45 miles per hour, engineers were concerned.
They had reason to be, said Ken Agent, a researcher at the University of Kentucky who has studied how high speeds can lead to more crashes at permissive left turns.
“Someone’s coming, and they think they have time to turn, and they don’t,” Agent said. “There is a lot less room for error when you increase the speed.”
Guidelines from the Federal Highway Administration still encourage local highway agencies to install protected left-turn signals where the speed is greater than 45 miles per hour. But now that drivers are more used to yielding, the flashing yellows can be installed safely on some roads with speeds over 45 miles per hour if they offer clear sightlines and traffic volumes are low, Agent said.
“You want to make things as safe as you can, but you want to be efficient,” he said. “If you wanted to make things as safe as you could, you’d put protected (signals) everywhere. But the most efficient way is the permissive/protected signals.”
Melder said the safest signal depends on the unique conditions of an intersection. “A protected left turn may appear to be safer, but if other driver behavior results in compromised safety we may find that permissive are actually safer,” he said.
Experimenting with left turns
In 2013, ACHD and ITD began an experiment. ITD requested that ACHD consider installing the flashing yellow arrows on some state highways where speed limits were 45 miles per hour or more, said ACHD General Counsel Steve Price.
In a letter to the Statesman, Price wrote that in choosing what roads to install the flashing yellow arrows on, “ACHD used industry standards and guidelines to determine whether drivers had adequate sight distance to decide whether to turn on a flashing yellow arrow indication. ACHD also looked at locations in other jurisdictions that had high-speed protected/permissive signal phasing, such as ITD’s flashing yellow arrow signal on State Highway 16 in Emmett.”
ACHD first tested the new signals at six locations on suburban, 55-mile-per-hour five-lane state highways.
“We explored it because ITD was pushing us to explore it,” Price said in an interview. “They’re very much about pushing efficiency in their system.”
ITD’s Melder declined to comment on Price’s remark.
By 2015, the test intersections averaged just one left-turn crash per intersection, with no fatalities or severe injuries, according to Price. In 2016, ACHD and ITD converted all protected left-turn signals on Idaho 44 in Eagle to flashing yellow arrows.
Since then, the Ada County Sheriff’s Office has counted four deaths at intersections with the flashing yellow arrows along Idaho 44.
Those deaths have prompted some changes. When a motorcyclist was killed by a car turning left from Idaho 44 onto Edgewood Lane in November 2016, ACHD and ITD decided to shut off that flashing yellow arrow.
Calley, the Eagle police chief, supports turning off the flashing yellow arrows at high-speed intersections at peak hours, as ACHD’s Wong has proposed. With 80,000 cars per day going through intersections like Idaho 44 and Eagle Road, he said it’s difficult for drivers to find time to turn.
He recognizes that it may not be a popular idea.
“Nobody really wants to be the person saying yes or no, but at some point we’ve got to try something,” Calley said.
ITD says it’s considering what to do.
“We are gathering and evaluating the data of that new signal function, but right now no decision has been made,” spokesman Jake Melder said.
ACHD is also studying crashes and safety data at all flashing yellow arrows in the county, Price said. He expects engineers will finish their analysis in September.
ACHD moves to protect pedestrians
Wong told a pedestrian advisory group in May that ACHD will also consider updating its pedestrian signals so that, when activated, they override the flashing yellow arrows. If the ACHD Commission agrees, all of the nearly 250 yellow arrow signals around the county will stop flashing when a pedestrian presses a button to cross the street.
In February, Boise residents Robert and Florence Goar, 89 and 87, were in a crosswalk when they were hit by a car turning left from Northview Street onto Milwaukee Street. The intersection features a flashing yellow arrow. Their death sparked calls from activists to make the intersections safer for pedestrians.
Price said the Goars’ death, and the subsequent activism, did not factor into ACHD’s possible update. A vendor’s software was just recently updated to allow such an override at the signals, he said.
A 2013 study from the Transportation Research and Education Center at Portland State University tracked drivers’ eye movements at intersections with flashing yellow arrows. The researchers found that drivers were so fixated on oncoming traffic that they spent little time looking for pedestrians. The more the number of oncoming cars increased, the less time drivers spent looking for pedestrians.
At certain intersections near schools, ACHD already stops a flashing yellow arrow signal when pedestrians push the button to cross. Drivers must then wait for a green-arrow left-turn signal.
Other communities have started rethinking flashing yellow arrows, too. Sugar Land, Texas and Washington County, Oregon updated their systems as early as 2013 to stop the flashing yellow when pedestrians are crossing.
Kostelec, the transportation planner, applauds ACHD’s decision to change the signals.
“Too often, I see agencies address traffic deaths as a one-off issue, addressing a specific location rather than looking systemwide,” Kostelec said. “This appears they used a pattern of severe and fatal crashes, as well as reports of near-misses across all modes, to help prompt a change that will benefit everyone from a safety perspective.”