Motorists travel east on state Highway 500 near the intersection with Falk Road. WSDOT officials removed a traffic signal at the intersection two years ago, which has so far resulted in a 68 percent decrease in accidents. (Photos by Amanda Cowan/The Columbian)Photo Gallery
It’s been a year since the Washington State Department of Transportation installed a pair of roundabouts on state Highway 14 in Washougal, and two years since the department removed two traffic signals along state Highway 500 in Vancouver.
The strategies were different — Highway 14 traffic has to slow down to pass through the roundabouts, while Highway 500 drivers can now zip through at full speed — but the projects shared a goal of reducing accident rates.
Early data from both corridors suggests that the changes are working as intended, particularly when it comes to stopping rear-end crashes.
The Highway 500 project ripped out the traffic signals at the intersections with Northeast 42nd Avenue/Falk Road and Northeast 54th Avenue/Stapleton Road, extending the median barrier through the intersections and converting the roads to right-in/right-out interchanges.
The Highway 14 roundabouts replaced the intersections at Washougal River Road/15th Street, which previously had a traffic signal, and 32nd Street, which did not.
The big caveat when evaluating the performance of both projects is that the updated intersections are all still too new to make apples-to-apples comparisons.
Both projects were designed based on traffic data compiled over a five-year period, WSDOT spokeswoman Tamara Greenwell said, so a true comparative analysis will require another three or four years of data. The study period needs to be long enough to account for unique weather conditions such as big snow storms, she said, as well as general fluctuations in accident rates from year to year.
Traffic lights
Data from the two years since the removal of the Highway 500 traffic lights shows a 68 percent reduction in crashes through the corridor, Greenwell said, compared with the five years that were used as the baseline beforehand. It’s almost an exact match for what WSDOT engineers hoped to see.
“When we looked at this project, the data supported that we’d see about a 70 percent reduction in crashes,” Greenwell said.
Highway 500 used to be notorious for rear-end crashes, which WSDOT attributed to drivers being caught off guard by the two traffic signals in the middle of a corridor that is otherwise built like a freeway. Those crashes have all but vanished in the past two years, Greenwell said, and other types of crashes, such as sideswipes, are down too.
The Stapleton Road intersection saw 193 crashes from 2012 to 2016, Greenwell said. From November 2018 to October 2020, there have been four. The Falk Road intersection also saw four crashes in the past two years, down from 109 during the earlier five-year period.
The decline in multi-vehicle crashes has been slightly offset by an increase in fixed-object crashes, meaning when a driver hits a stationary object like a road sign or a plastic delineator pole. There were 14 such accidents at the Stapleton Road intersection during the original five-year monitoring period, Greenwell said, and 19 in the past two years.
WSDOT generally tends to see slightly higher numbers of fixed-object crashes in the first year after new traffic configurations are implemented, she said, which is another reason why it’s important to wait the full five years before drawing official conclusions.
“Oftentimes people drive on autopilot, and more and more we’re seeing distracted driving,” she said.
Roundabouts
The initial data from the Highway 14 roundabouts shows a marked decrease in the severity of accidents, although not a major decrease in the number of accidents overall. However, Greenwell stressed that a true comparison will need five years of data, and it’s barely been a year since the traffic circles debuted.
There were five crashes in corridor in the past 11 months, compared with 28 during the five-year study period. But the earlier crashes included 25 rear-end collisions at the Washougal River Road intersection, Greenwell said — and in the past year, there’s been just one. Fixed-object crashes have risen slightly, from zero before to two in the past year.
The removal of the traffic signal at Washougal River Road makes a big difference, Greenwell said, because it eliminates the risk of drivers trying to run the light or mistakenly thinking they have more time before it changes — two of the most common causes of accidents before the roundabout project.
It also gets rid of a potentially unexpected stop; the Washougal River Road intersection was the only traffic signal on Highway 14 in all of Clark County.
The traffic circle design naturally results in less-severe accidents because the Highway 14 lanes go through chicane curves as they approach the intersection, she said, prompting drivers to slow down.
The $7.5 million roundabout project was a more extensive update than the roughly $860,000 traffic signal removal on Highway 500, but both methods were chosen in part because they could be implemented relatively quickly and cheaply.
A full freeway interchange on either highway would have been far more expensive, Greenwell said, because of the need to build a bridge to grade separate the roads. For comparison, the 2017 upgrade to the Interstate 5 interchange near ilani cost $32 million, and the Interstate 205 interchange at Northeast 18th Street cost of $40.6 million.
Morning Briefing Newsletter
Get a rundown of the latest local and regional news every Mon-Fri morning.
