Nationwide figures show that traffic deaths are dropping as gas prices climb.

The National Safety Council reports a 9-percent drop in motor vehicle deaths through May, compared with the same time period last year. Researchers say that includes an 18-percent drop in March and 14 percent in April.

Preliminary figures obtained by The Associated Press show some states reporting 20-percent declines in traffic deaths — or more.

No one is saying for certain why road fatalities are decreasing, but the drop comes as Americans cut back sharply on driving because of record-high gas prices.

The last time road deaths fell this quickly and this sharply was more than 30 years ago: during the Arab oil embargo of 1973-1974. After states raised the drinking age to 21 from 1982-1983, traffic fatalities fell 11 percent.