State report: "Rumble strips" on state highways cut accidents by nearly 60 percent

An analysis of state highways has found that centerline rumble strips, the grooves cut into pavement on 2,000 miles of the state's two-lane highways, has reduced serious injury and fatal crossover collisions by 57 percent.

The reported is included in the latest Gray Notebook, a quarterly update provided by the state Department of Transportation.

It found that the rumble strips, which have been in place since 1995, is most effective when the driver is tired or distracted and his car drifts over the center line.

Today the state has strips on 38 percent Washington's 5,250 miles of two-lane highways, said Jason Nye, with the DOT. They aren't on any freeways.

The state is installing another 650 miles of them.

According to the state study, the rumble strips show a 24 percent reduction in serious and fatal injury collisions on curves and a 52 percent reduction of accidents on straight roadways.

The state analyzed more than 6,800 police collision reports from 2002 through 2008 where rumble strips have been installed. It showed a 58 percent reduction in accidents where the driver was tired, a 59 percent reduction where the driver was distracted, a 45 percent reduction where the driver was speeding and a 43 percent reduction where the driver was intoxicated.

In other findings:

• The number of median collisions grew between 1995 and 2008, but serious injuries dropped by 59 percent and fatal collisions by 25 percent.

• The 522 traffic fatalities last year were the fewest since 1955, when there were 461.

For 2008, the miles traveled on state highways decreased about 3.8 percent from 2007, which may have contributed to the lower fatality rate, said the DOT. . Over the past 18 years, the fatality rate on all Washington roads — state, city and county — has decreased 49 percent.

Washington is third highest in the nation in seat belt use.

The state's fatality rate is nine fatalities per 100,000 people, far below the national average of 14.

• During the first half of 2009, travel times during peak periods improved on 13 of 18 commuter routs in the Seattle area. The DOT attributes this to unemployment due to the economic recession.

Susan Gilmore: 206-464-2054 or sgilmore@seattletimes.com