Home » News
IIHS News | January 14, 1999Subscribe

Motor vehicle deaths 15 percent higher on roads in 24 states that raised speed limits

ARLINGTON, Va. — The higher speed limits introduced in 24 states during late 1995 and 1996 resulted in increased motor vehicle deaths during 1996-97. Insurance Institute for Highway Safety researchers compared the numbers of motor vehicle occupant deaths in these 24 states from the time speed limits were raised through 1997 with corresponding fatality counts for the same months in the six years before the speed limits were changed. As a control, researchers also analyzed deaths in seven states where speed limits weren't changed during the study period. To account for increases in miles traveled, analyses then were conducted using fatality rates per vehicle mile instead of fatality counts.

Based on these studies, the Institute estimates an increase in deaths on interstates and freeways of approximately 15 percent. Meanwhile, deaths didn't increase at all on interstates and freeways in states where speed limits weren't raised. These findings expand earlier Institute research conducted in 12 states that raised speed limits beginning in December 1995. The earlier study found a 12 percent increase in deaths on roads where speed limits were raised.

Motor Vehicle Deaths on Interstates and Freeways, 1990-97

Graph image

 24 states where speed limits were changed7 states without speed limit changes
19902,932458
19912,787408
19922,730382
19932,768416
19942,973445
19953,100440
19963,604446
19973,504437
Note: Fatality counts shown in BOLD reflect speed limit increases during late 1995 and 1996.

Other Institute research indicates that travel speeds went up on roads in states that raised limits after Congress repealed the national maximum speed limit in late 1995. The 24 states the Institute studied raised speed limits to 70 mph or higher on rural interstates and to 60, 65, or 70 mph on urban interstates and freeways. Some states, such as Texas, raised speed limits even on two-lane highways. Montana doesn't post a numeric speed limit at all for cars during the day.

"It's clear from this study that the current round of speed limit increases on rural interstates in the 1980s is costing hundreds of lives per year," Institute president Brian O'Neill says. "This cost could go up in the future because research shows actual speeds continue to rise in the years following a speed limit change."

Speeding reduces the time drivers have to avoid crashes. It increases the likelihood of crashing and the severity of the crashes that occur. "We know that when speed limits are raised," O'Neill says, "drivers who exceeded the old speed limits will exceed the higher limits, too, because people take note of the limits and then travel faster, at speeds at which they believe they won't get a ticket."

©1996-2014, Insurance Institute for Highway Safety, Highway Loss Data Institute | www.iihs.org