The number of traffic fatalities in 2008 was the lowest in Washington state since 1955, according to new data from the state Department of Transportation and the Washington Traffic Safety Commission.

To date, 522 deaths have been reported for 2008, according to a news release from the State Patrol. That's the lowest total since 1955, when 461 people died on Washington state roads. The 2008 count will not be final until Dec. 31, and delayed reports of fatalities could still come in.

The reduction has been attributed to the increased use of seat belts. The number of deaths involving motorists not wearing seat belts has dropped by more than a third since 2000.

"We have been strictly enforcing the state's seat belt law, and that appears to be paying dividends," said State Patrol Chief John R. Batiste said in the news release. "There's no simpler way to protect yourself from the other driver's mistake than to buckle your seat belt."

Washington's seat belt usage rate of 96.5 percent is the third-highest in the nation, behind only Michigan and Hawaii.

Initially, the drop in fatalities was believed to be due to a reduction in driving because of high gasoline prices and the recession. However, the number of fatalities was measured against total miles driven to determine the "fatality rate" -- the number traffic deaths per 100 million vehicle miles traveled (VMT.)

Washington's traffic fatality rate in 2008 was .94 deaths per 100 million VMT. That's down slightly from 1.00 in 2007, and about half the 1990 rate of 1.85 deaths.

The number of collisions is also dropping. In 1990 there were nearly 2,500 fatal or serious injury collisions. By 2008, that number had dropped to just over 1,000, according to the State Patrol.