Columbus, Ohio — Rising prices at the gas pump appear to be having at least one positive effect: Traffic deaths nationwide are plummeting, just as they did during the Arab oil embargo three decades ago.

Researchers with the National Safety Council report a 9 percent drop in motor vehicle deaths overall through May compared with the first five months of 2007, including a drop of 18 percent in March and 14 percent in April.

Preliminary figures show some states have reported declines of 20 percent or more. Thirty-one states have seen declines of at least 10 percent, and eight states have reported an increase, according to the council.

No one can say definitively why road fatalities are falling, but it is happening as Americans cut back sharply on driving because of record-high gas prices.

Fewer people on the road means fewer fatalities, said Gus Williams, 52, of Albany, Ga. "That shows a good thing coming out of this crisis." He has also noticed that many motorists are going slower.

The federal government reported in April that miles traveled fell 1.8 percent in April compared with a year earlier, continuing a trend that began in November.

Experts say a slumping economy and fuel prices have brought down the number of road fatalities.

"When the economy is in the tank and fuel prices are high, you typically see a decline in miles driven and traffic deaths," said John Ulczycki, the council's executive director for transportation safety.

Indiana fatalities are down 26 percent and on pace to surpass the lowest level since the state first began keeping records 18 years ago: 792 fatalities in 2002.

Ohio's rate is off 20 percent, and the state recorded just six deaths during the Memorial Day weekend, the fewest in 38 years. Illinois' total also is off 20 percent.

Preliminary figures show death rates are down 20 percent in Tennessee, 22 percent in New Jersey, 13 percent in Washington state, 11 percent in Florida and 21 percent in New Mexico, where the state effort to cut alcohol-involved fatalities has resulted in a 35 percent decline in such deaths so far this year, from 83 to 54.

The last time road deaths fell this fast and this sharply was during the Arab oil embargo in 1973-1974, when fatalities tumbled 17 percent, from about 55,100 to 46,000; and as states raised the drinking age to 21 in 1982-83, when fatalities fell 11 percent, from roughly 49,300 to 44,000.

Fatality rates have remained relatively flat during the last 15 years or so, totaling 42,642 in 2006, the last year for which complete figures from the National Highway Traffic Safety Administration are available.