COLUMBUS, Ohio — Rising prices at the gas pump appear to be having at least one positive effect: Traffic deaths around the country 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 obtained by the Associated Press show that 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., who frequently drives to northern Ohio. “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.

The last time road deaths fell this fast and this sharply was during the Arab oil embargo in 1973-74, 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.

Chuck Hurley, a former official with the National Safety Council and the Insurance Institute for Highway Safety, said half of the decline in road deaths during the 1970s was attributed to high gas prices. The remainder was linked to the lowering of freeway speed limits to 55 mph.

Republican Sen. John Warner of Virginia has said Congress might want to consider reimposing a national speed limit.

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.

After the energy crisis of the 1970s, traffic fatalities gradually crept up in the 1980s as gas prices dropped and speed limits began to rise again.

But the number of fatalities may continue falling if oil futures contracts are any indication. Most energy traders do not foresee a long-term decline in prices, despite a big decrease last week and another one Tuesday.

“People aren’t driving as much. We’re definitely seeing a difference” in crashes, said Pam Fischer, director of the New Jersey Division of Highway Safety.