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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research confirmed that travel speeds are higher on roads in states that raised limits after Congress in late 1995 repealed the national maximum speed limit.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
StateDate of changeRural InterstatesUrban interstates/freeways
Old limit
(mph)
New limit
(mph)
Old limit
(mph)
New limit
(mph)
ArizonaDec. 8, 1995657555no change
CaliforniaJan. 7, 199665705565
KansasMar. 7, 199665705570
MississippiFeb. 29, 199665705570
MissouriMar. 13, 199665705560
MontanaDec. 8, 199565none55none
NevadaDec. 8, 199565755565
OklahomaDec. 15, 199565705560
 Aug. 29, 1996 75 70
South DakotaApr. 1, 199665755565
TexasDec. 8, 199565705570
WashingtonMar. 15, 199665705560
WyomingDec. 8, 199565755560

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