Speed limits definitely matter to insurance companies, law enforcement agencies, state transportation departments, and national safety organizations, but do they matter in terms of preventing accidents?

There is no absolute proof that they do, but there’s plenty of speculation.

According to the Insurance Institute of Highway Safety (IIHS), more than 10,000 deaths occurred in speed-related accidents in 2012, and the enforcement of speed limits helps keep speeds down. Crash rates are actually the lowest for drivers traveling near the mean speed, and increase with deviations above and below the average. Low-speed drivers are more likely to be involved in accidents than relatively high-speed drivers.

Only one industrialized country, Germany, does not limit speeds on its public highways, and significant portions of the Autobahn do not have speed limits, according to motorists.org. Although some vehicles have been clocked traveling faster than 150 mph on the Autobahn, the average speed is actually around 80 mph, and the fatality rate is lower than the fatality rate on some rural U.S. interstates.

Simple Physics?

IIHS spokesman Russ Rader, quoted recently in the Los Angeles Times, said it’s just a case of simple physics:

The research is clear and consistent on the safety consequences of raising speed limits. Higher speed limits get people to their destinations faster, but there’s always a cost: Ultimately, there will be more severe crashes and more deaths on those roads.

Speed limits are rising across the U.S., particularly in western states like Wyoming, Idaho, and South Dakota. Utah officials have said that since 2008, when they raised the speed limit to 80 mph on rural Interstate 15, car accidents have dropped annually and drivers complied better with the new limit than the previous 75 mph.

Although the Utah Highway Patrol has spoken out against higher speed limits, in December 2014, the state raised the speed limit from 65 to 70 on urban interstates around Salt Lake City. After studying speed patterns on Wasatch Front urban interstates, UDOT officials concluded that most traffic was already traveling much faster than 70 mph on those freeways and the higher speed allowance will promote consistency and reflect the speeds motorists are already driving.

The Value of Speed Limits

Speed limits have value, especially if they’re established for the right reasons, which include:

  • Informing motorists about what a safe and efficient speed is for a given highway during normal driving conditions
  • Establishing a smooth traffic flow that most vehicles should try to emulate
  • Encouraging good lane discipline through comparably uniform vehicle speeds

Colorado law calls for reasonable and prudent speeds, meaning motorists shouldn’t go faster than what is safe for the road conditions. The maximum speed limit on rural freeways and interstates in Colorado is 75 mph, or 65 mph on urban freeways and interstates. In most cases, the speed limit will return to the rural freeway speed limit of 75 mph once the road passes through densely populated areas.

Image by Nelson Pavlosky

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