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IIHS News | October 10, 1997Subscribe

Motor vehicle fatalities in 1996 were 12 percent higher on interstates, freeways in 12 states that raised speed limits

ARLINGTON, Va. — Five hundred more people died in motor vehicle crashes in the last 9 months of 1996 than would otherwise have been expected in the 12 states that raised speed limits on interstates and freeways between December 8, 1995 and April 1, 1996, a new Insurance Institute for Highway Safety study estimates.

Researchers compared the numbers of motor vehicle occupant deaths between April and December 1996 in 12 states with corresponding fatality counts for the same 9-month periods in 1990-95, as well as fatality counts from 18 states that didn't change maximum speed limits during 1996 or that raised speed limits on fewer than 10 percent of urban interstate roadways.

The Institute estimates a 12 percent increase in fatalities on interstates and freeways and a 6 percent increase on all roads in these 12 states.

"The actual increase in highway fatalities for the entire nation was probably greater than the study sample indicates," says Adrian Lund, Institute senior vice president. "This is because the 500 additional deaths on all roads represents a 9-month period only and doesn't include deaths in another 12 states that raised limits later in the year."

Repeal of maximum speed limit brought higher speeds

Earlier Institute research confirmed that travel speeds are higher on roads in states that raised limits after Congress in late 1995 repealed the national maximum speed limit. The 12 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 daytime.

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

Speeding is one of the most prevalent reported factors associated with crashes. It reduces the time drivers have to avoid crashes and increases the likelihood of crashing and the severity of crashes that do occur. "We know that when speed limits are raised," Lund 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."

Speed limit changes: late 1995/early 1996 in 12 states
State Date of change Rural Interstates Urban interstates/freeways
Old limit
(mph)
New limit
(mph)
Old limit
(mph)
New limit
(mph)
Arizona Dec. 8, 1995 65 75 55 no change
California Jan. 7, 1996 65 70 55 65
Kansas Mar. 7, 1996 65 70 55 70
Mississippi Feb. 29, 1996 65 70 55 70
Missouri Mar. 13, 1996 65 70 55 60
Montana Dec. 8, 1995 65 none 55 none
Nevada Dec. 8, 1995 65 75 55 65
Oklahoma Dec. 15, 1995 65 70 55 60
  Aug. 29, 1996   75   70
South Dakota Apr. 1, 1996 65 75 55 65
Texas Dec. 8, 1995 65 70 55 70
Washington Mar. 15, 1996 65 70 55 60
Wyoming Dec. 8, 1995 65 75 55 60

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