The Arab oil embargo in mid-October 1973 curtailed availability of gasoline. Fuel conservation measures resulted in reduced travel and decreased traffic speeds. On March 1, 1974, posted speed was set at 55 mph (88 km/h) on rural highways in Kentucky. Traffic volumes, speeds, and accidents for the rural highway during the period known as the "energy crisis" and its after effects were compared to the corresponding period a year earlier.

Traffic volumes began to decline in December 1973 and continued through September 1974. Total travel in the 12 months through November 1974 decreased by 2.3 percent; traffic increased by five percent in 1973. Accident rates during this period decreased by 13.5 percent; and the largest decreases were associated with the highways experiencing the greatest reductions in travel speed. The relationship between traffic speed and accident rate showed a great decrease in accident rate as traffic speeds decreased. Differences between wet-surface and dry-surface accident rates were especially significant and were more so for interstate than for two-lane highways. Improved wet-pavement skid resistance at the lower speeds obviously contributed to a reduction in accident rates. Continuation of the 55-mph (88 km/h) speed limit on all rural highways would seem advisable.

Report Date


Report Number

No. 430

Digital Object Identifier



Offered for publication to the Transportation Research Board.