WASHINGTON — American motorists, paying record prices for gasoline, drove less for a seventh consecutive month in May, pointing toward the first annual drop in road travel since 1980.

“$4 per gallon may have been the trigger point we’ve been looking for,” the managing director for travel and tourism at the consulting firm Global Insight Inc. in Lexington, Massachusetts, Kenneth McGill, said. “It’s interesting to see Americans finally reacting to the price of gasoline by rationing consumption.”

Vehicle-miles traveled on all American roads fell 3.7% in May from a year earlier, the Federal Highway Administration said in a report yesterday. The seven-month slide is the longest streak since 1979, an agency spokesman, Doug Hecox, said.

Drivers cut back as the average American retail gasoline price reached a then-record of $3.98 a gallon on May 31. Rising fuel prices and a weak economy also marked the drop in driving in 1980, after the Soviet Union invaded Afghanistan and American Embassy personnel in Iran were taken hostage.

May’s travel decline pushed this year’s total down 2.4%, according to the Washington-based highway agency, which has been reporting the data since 1942.

Driving decreased in all five regions for which the agency tallies results, led by a 4.5% drop in north-central America, which includes Chicago. May’s 254.7 billion miles driven were the lowest for the month since 2003.

The report adds to evidence of a slowing American economy already beset by the worst housing market since the Great Depression. Gasoline at American pumps averaged as high as $4.11 this month before slipping to $3.96 on Sunday, according to motoring group AAA. Spending more on fuel leaves consumers with less for other goods and services.