A study by two College Park researchers found a significant increase in fatal accidents after 1986 in small states that increased the speed limit to 65 mph on rural interstates. But the study also found that the number of those accidents began to fall back after about a year, perhaps as motorists became more adept at faster driving.
The study by professors Everett C. Carter and Gang-Len Chang, both of the University of Maryland's Transportation Studies Center, also found that larger states that have discarded the 55 mph limit -- such as California, Texas and Florida -- saw no significant long-term change in highway mishaps between 1987 and 1989.
And, they found, the accident rates in Maryland and New York, which kept the 55 mph limit, also remained "quite stable" over the same period.
But the study, underwritten by the American Automobile Association Foundation for Traffic Safety, isn't likely to end the debate over the wisdom of raising the 55 mph speed limit in about 10 states, including Maryland, that have not done so.
That's because the researchers warned that there is still not enough data "for a proper assessment of any safety policy impact."
Earlier this year, the Maryland General Assembly passed a bill that would have established a speed limit of 65 mph on about 120 miles of interstate highway in rural areas. But Gov. William Donald Schaefer vetoed the bill in May, saying it would lead to more traffic fatalities and serious injuries and would mean the use of more gasoline at a time when fuel should be conserved.
A number of conflicting traffic safety studies have been published on the 65 mph limit since 1987, when Congress permitted states to adopt it.
The authors of the University of Maryland study wrote that their findings should "be regarded as preliminary" because they were not able to screen out the effects of the "random fluctuation" in the number and type of accidents, which depend on such unpredictable factors such as driving behavior and weather.
And, they added, two years was not long enough to yield "definitive" data on accident rates.
Congress imposed the national 55 mph speed limit in 1974 as a gasoline conservation measure. In 1987, lawmakers backtracked and permitted states to return to the 65 mph limit on rural stretches of interstates.