Managing speed: interagency collaboration could curb speeding and save lives

Public Roads, Jan-Feb, 2003 by Elizabeth Alicandri, Davey L. Warren

The twin challenges of the transportation system are to move traffic safely and efficiently. Although highways and motor vehicles are designed to operate safely at speeds traveled by most motorists, almost one in every three traffic fatalities in the United States is related to speeding, either involving exceeding the posted speed limit or driving too fast for conditions.

In 2000, more than 12,000 lives were lost in speeding-related crashes, and more than 700,000 people were injured. The National Highway Transportation Safety Administration (NHTSA) estimates that speeding-related crashes cost society $28 billion annually. That's $53,243 per minute, or almost $900 per second.

Because speeding is a complex problem involving many factors--personal behavior, vehicle performance, roadway characteristics, and enforcement strategies--the U.S. Department of Transportation (USDOT) organized a multidisciplinary, multiagency team to tackle the problem. The USDOT Speed Management Team includes personnel from the Federal Highway Administration (FHWA), the Federal Motor Carrier Safety Administration (FMCSA), and NHTSA, representing backgrounds ranging from traffic engineering and enforcement to psychology and marketing.

According to Earl Hardy, a highway safety specialist and the speed management team coleader for NHTSA, approaching the problem of speeding in a coordinated fashion enables the team to develop the best solutions to combat speeding more effectively.

He says, "Through collaboration, we can approach the speeding issue holistically gathering and analyzing data, setting appropriate speed limits, improving engineering and enforcement technologies, developing innovative strategies for speed enforcement, and educating practitioners, policymakers, and the public about effective solutions."

Public Policy and Outreach

From a public policy standpoint, an effective speed management policy needs to overcome a variety, of obstacles in public perception. One of: the most common speeding issues brought to the attention of policymakers is that, citizens are concerned about other drivers speeding through their neighborhoods, yet most citizens have no idea what goes into setting appropriate speed limits.

Traffic engineers and law enforcement officials need to educate citizens on what speed limits can (and cannot) do in terms of improving safety on roadways. Posting a lower speed limit sign, for example, may help neighborhood residents feel safer, but it will not necessarily slow traffic. In fact, according to research conducted by FHWA in 1997, raising and lowering speed limits as much as 32 kilometers per hour, km/h (20 miles per hour, mph) has little or no effect on prevailing speeds.

Political pressures also factor into speed management policy. Elected officials ,must answer to constituents who are reluctant to see more speeding tickets issued in, their communities or concerned about the use of unconventional police vehicles. In addition, citizens raise the privacy issue with regard to the use of photo radar to enforce speeding, calling for less government intrusion into people's lives. For photo radar enforcement to be acceptable to communities, officials need to focus attention on safety, rather than revenue enhancement.

Engineering

Appropriately engineered speed limits are an essential element in highway safety. For speed limits to be effective, however, they must appear reasonable to most drivers and correctly reflect the maximum safe speed for prevailing conditions. Otherwise the legal system misallocates resources dealing with motorists who are technically violating the law but not engaged in any high-risk behavior. Thus, a prerequisite to an effective speed management program is the establishment of realistic speed limits that are consistent with the road environment.

FHWA's Manual on Uniform Traffic Control Devices recommends that speed limits be set at the 85th percentile speed, or the speed at or below which 85 percent of all the vehicles travel when passing a given point on the road. Only 15 percent of vehicles are traveling above the 85th percentile speed--or speeding.

Setting speed limits based solely on the 85th percentile speed, however, does not account for other factors like roadside development, pedestrian activity, or accident experience. FHWA is developing a software program--USLIMITS--that will help safety engineers systematically and consistently account for these other factors in determining appropriate speed limits. Practitioners are beta testing USLIMITS to evaluate the reasonableness of the recommended speeds, and FHWA expects to release the software in early 2003.

Research indicates that the risk of crash involvement is lowest for motorists traveling near the average speed of traffic and is significantly higher for the fastest 2 to 5 percent. Setting speed limits at the 85th percentile speed of traffic, allowing for a tolerance of no more than 8 km/h (5 mph), would focus enforcement and adjudication on the occasional violators and high-risk drivers.