A survey of state highway safety agencies found that traffic deaths were down in 40 states. The Governors Highway Safety Association said the average decline was 10.7 percent.

In South Dakota, the decline was 17 percent. Preliminary figures from the state's Department of Public Safety show 121 traffic deaths last year, down from 146 in 2007.

Barbara Harsha, executive director of the Governors Highway Safety Association, said high gas prices that curtailed travel early in the year and a poor economy in the second half of 2008 were factors.

"However, states are reporting that other factors such as better laws, record high safety belt use and reduced speeds played a role," she said.

In South Dakota, the decline in deaths probably was a result of several factors, including proactive law enforcement and new educational programs aimed at saving lives, said J.C. Carpenter, director of the state's Office of Highway Safety.

Alaska, Hawaii, Massachusetts, Virginia, Wisconsin and the District of Columbia all saw declines of 20 percent or more. The only states reporting increases were Delaware, New Hampshire, Vermont and Wyoming. Data have not been compiled yet for California, New York, Pennsylvania and Texas.

The Federal Highway Administration has reported steep declines in the number of miles Americans are driving each month beginning in late 2007 and continuing through the first three quarters of 2008.