Higher Speed Limits Cost Lives, Researchers Find

The research is published in the September issue of the American Journal of Public Health. It is the first long-term study to evaluate the impact of repealing the National Maximum Speed Law on road fatalities and injuries in fatal crashes between 1995 and 2005.

The law, which restricted the maximum speed limit to 55 mph on all interstate roads in the United States, was initiated in 1974 in response to the oil embargo and had an immediate impact.

"During the first year there was a drop of almost 17 percent in fatalities after the speed laws were reduced to 55 miles per hour," said Lee Friedman, assistant research professor of environmental and occupational health sciences at UIC and lead author of the study.

The law was modified in 1987 and allowed states to raise the legal speed limits to 65 mph on some interstates. In 1995, the federally mandated 55 mph speed law was revoked, allowing states to set their own speed laws.

"The primary finding of our study was that over the 10-year period following the repeal of National Maximum Speed Law, there were approximately 12,500 deaths due to the increased speed limits across the U.S.," said Friedman.

The researchers used a mixed-regression model to take into account when the speed limits changed in each state and the different characteristics within and between each state, such as car volume density, population density, variations in fleet sizes, the types of vehicles on the road, vehicle quality (newer vehicles versus older vehicles), as well as driver characteristics.

The primary flaw of previous studies has been that they have only focused on selected states or regions, said Friedman, or they have used a simple analysis to look at before versus after implementation of the law during a very short period of time.

The researchers suggest that policy makers reevaluate national policy on speed and road safety and consider reduced speed limits and improved enforcement with speed camera networks to save lives.

Speed camera programs have been implemented in England, France and Australia and have shown immediate reductions in motor vehicle crash fatalities, said Friedman.

"This is a failed policy because it was, in essence, an experiment over 10 years. People assumed that increasing the speed limit would not have an impact," said Friedman. "We've shown that something has happened and it's quite dramatic."

Friedman uses the example of the 3,000 people who died in the September 11th terrorist attacks.

"That tragic event has led to a whole foreign policy," he said. "We estimate that approximately 12,500 people died as a result of a policy to deregulate speed enforcement -- four times what happened on September 11th -- and yet changing the policy to reduce speed limits may be very difficult."

Friedman's co-authors are Donald Hedeker, UIC School of Public Health, and Elihu Richter, Hebrew University, Jerusalem.