Higher Speed Limits Didn't Increase Statewide Crashes in California
10 March 2000
New Study Shows Higher Speed Limits Didn't Increase Statewide Crashes in California
LOS ANGELES--March 10, 2000--A new study on the safety of speed limits by the Automobile Club of Southern California shows that the higher speed limits set in California during the mid 1990s did not increase the rate of fatal and injury traffic crashes.This is the first study to offer an in-depth analysis of the effects of higher speed limits in California.
The study by Steven Bloch, Ph.D. of the Auto Club and Dave DeYoung of the California Department of Motor Vehicles evaluated how higher speed limits affected crash rates (per mile driven) in California after the maximum speeds were increased in December 1995 and in April 1996. These increases on approximately 6,000 miles of California roads followed the repeal of the national maximum speed limit.
Speed limits were increased from a statewide 55 miles per hour to 65 and 70 miles per hour depending on the type of roadway. The authors studied crashes on all roadways in the state, not just those affected by increased limits because drivers may choose a different route due to higher speed limits. This choice could affect crash rates.
Bloch and DeYoung found that immediately after the 1995 increase, there was no change in the rate of fatal or serious injury crashes. Less serious injury crashes, however, increased temporarily, but then declined. After the April 1996 speed limit increase, the rate of fatal crashes declined. The study also found evidence that the rate of injury crashes dropped.
"Considering all these findings, we concluded there is no evidence that the increased speed limits in California compromised the general level of traffic safety in the state," said Bloch.
One possible reason for the surprising effect is that actual travel speeds did not change much, only by one or two miles per hour, according to Bloch. Drivers apparently were already going faster than the old speed limits, and didn't exceed the new limits by the same margin.
Another possible reason is that the raised speed limits had an effect on the entire highway system, not just on the roads where limits changed. "It's possible that as speed limits rose, traffic flowed from more dangerous local roads to larger, divided highways, which are much safer," explained Bloch.
"Police may also have re-allocated their enforcement resources toward catching the most dangerous drivers rather than focusing their limited resources on monitoring and catching drivers exceeding 55."
Bloch stressed that the study does not show that driving faster is safer than driving at a moderate speed. "Faster-moving vehicles are more likely to crash because the driver has less time to brake and a smaller margin of error in an emergency. Faster-speed crashes are also more likely to result in injury or death because fast-moving objects hit with greater force than slow-moving ones."
This study, according to Bloch, does support the idea that the policy of raising speed limits on interstates and other roads where higher limits are appropriate is not necessarily harmful to overall traffic safety in a state. "Any revised speed limit must be carefully considered before speed limits are raised," he said.
"The type of road, design characteristics and general speed patterns need to be taken into consideration to preserve the safety of the road."
Several multi-state and state-specific studies conducted after the partial repeal of the national maximum speed limit (NMSL) in 1987 also found that increased speed limits do not lead to increased crashes when all roads in a state, not just the ones with increased limits, are taken into account.
This is the first state-specific study to conclude that higher speed limits did not increase crashes on all roadways in a state since the NMSL was fully repealed in 1995.
Free copies of the study "Traffic Safety Impact of 1995-1996 Increases In California's Speed Limits" are available by calling the Auto Club's Public Affairs office at 714/885-2300 or by sending an e-mail to corpcommunicate@aaa-calif.com.
The Automobile Club of Southern California, the largest affiliate of the AAA, has been serving members since 1900.
Today, the Auto Club's members benefit by the organization's roadside assistance, financial products, travel agency and trip planning services, highway and transportation safety programs, insurance products and services, automotive pricing, buying and financing programs, automotive testing and analysis and legislative advocacy.
Information about these products and services is available on the Auto Club's Web site at www.aaa-calif.com.
