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The Results are in…Fewer Collisions on Northeast 125th!

In May 2011 the Seattle Department of Transportation (SDOT) reconfigured the lanes on NE 125th Street between Roosevelt Way NE and 30th Avenue NE to make the street safer for everyone, better support transit and keep vehicles moving. Prior to the rechannelization there were two travel lanes in each direction. SDOT altered the road’s striping to provide one lane in each direction, a new two-way left turn lane and bicycle lanes.

SDOT agreed to monitor the project’s impact on safety and traffic after the rechannelization was completed to make sure the street functioned well. Data shows it is and we want to share the key results.

Prior to the project, the 85th percentile speed (the speed most drivers are comfortable driving) was 41 m.p.h. eastbound and 39 m.p.h. westbound. Eighty-seven percent of drivers were traveling over the speed limit and 16 percent of drivers were speeding at 40 m.p.h. or more – more than 10 m.p.h. over the speed limit! Since the project was completed, the 85th percentile is now 38 m.p.h. eastbound and 36 m.p.h. westbound with an 11 percent decrease in the percentage of people exceeding the speed limit.

And there has been an even more dramatic decrease in drivers speeding more than 10 miles over the speed limit!

The most dangerous drivers are now going slower.

While some worried about traffic diverting from the street, the opposite has occurred. Data indicates that traffic volume overall has increased roughly 10 percent on NE 125th. One possible factor in explaining this increase may be traffic is actually diverting to the road following the tolling of the SR520 floating bridge.

In one of the most satisfying outcomes, the rate of collisions and the rate of injury collisions have both declined. Despite the increase in traffic volume, the rate of collisions has decreased by 10 percent and injury collisions have decreased by 17 percent. This means that all of us – people who walk, ride a bicycle and drive – are safer when we use NE 125th. Modifying roads to discourage speeding is one of the recommended actions in Seattle’s Road Safety Action Plan, which has a goal of zero traffic fatalities and serious injuries by 2030.

All of this leads to fewer collisions.

These findings are similar to a recent Federal Highway Administration study – “Evaluation of Lane Reduction ‘Road Diet’ Measures on Crashes” – which analyzed 30 street reconfigurations in Washington and California. The federal agency determined there was a 19 percent reduction in the collision rate after converting from four-lanes to two lanes with a two-way left turn lane.

Once again Seattle has another successful rechannelization project, adding to the string of positive road reconfigurations the city has completed since 1972. To read the full report and see its data, click on this link: NE 125th Street Rechannelization Report.