Opinion: Make Mandating Speed Limiters a Top Priority

By Rob Abbott

Vice President of Safety Policy

American Trucking Associations

This Opinion piece appears in the April 9 print edition of Transport Topics. Click here to subscribe today.

Each year, the Department of Transportation undertakes a number of new initiatives to further reduce or eliminate highway crashes. One measure DOT has announced it will undertake this year will have a marked effect on highway safety: mandating that speed limiters on large trucks be set at a reasonable top speed.

A quick review of available safety data confirms that the single greatest contributor to highway crashes is vehicle speed. According to the Federal Motor Carrier Safety Administration’s Large Truck and Bus Crash Facts 2009, for instance, driving too fast for conditions or in excess of posted speed limits by the truck driver were factors in 13.9% of single-vehicle crashes and 5.9% of multiple-vehicle crashes that resulted in a fatality — more than any other factor.

Also, according to the University of Michigan’s Trucks Involved in Fatal Accidents data, speeding on the part of the truck driver was the most prevalent driver-related factor cited in fatal accidents involving a large truck.

In addition, the FMCSA Large Truck Crash Causation Study found that “traveling too fast for conditions” was cited as the critical pre-crash event in 18% (weighted estimate) of crashes where the truck was assigned the critical reason for the crash. This was the single most frequently cited factor in crashes where trucks were assigned a critical reason for the event.

Naturally, speed limiters won’t prevent all of these crashes — especially those involving drivers exceeding lower speed limits (e.g., 45 mph) or those involving drivers operating below the posted limit, but too fast for current conditions.

However, there is no question that the limiters will help to eliminate a great many crashes that occur at higher speeds. Preventing these crashes should be a priority because high-speed crashes tend to be more severe.

The fact that speed plays such a prominent role in highway crashes simply makes sense. Faster speeds lengthen stopping distances and limit a driver’s time to react to unforeseen circumstances and take evasive maneuvers to avoid a crash.

When a crash does occur, speed increases the severity of the event dramatically. For instance, a 30% increase in speed results in a 69% increase in the kinetic energy of the vehicle. That’s because kinetic energy is determined by the square of the vehicle’s speed, rather than by speed alone. In other words, as speed increases, energy increases at a much faster rate. For these reasons, new research on speed limiters recently released by FMCSA found that, “Multiple analyses indicated a profound safety benefit for trucks equipped with an active speed limiter.”

Lower speeds make economic and environmental sense as well. Fleets that voluntarily limit their speeds have seen cost savings not only from crash reductions, but from reduced vehicle maintenance, fuel use and other operating costs. If all fleets were to limit their speed, society would realize these benefits as well as reduced emissions and other positive environmental effects.

For these reasons, both American Trucking Associations and Roadsafe America petitioned the National Highway Traffic Safety Administration and FMCSA in 2006 to require that speed limiters be set on all commercial motor vehicles weighing more than 26,000 pounds. Fortunately, NHTSA granted the petitions in late 2010 and agreed to conduct a rulemaking, which is due to begin later this year.

The costs to impose such a mandate would be small. All heavy trucks manufactured since 1992 have speed limiter capabilities within their electronic control modules (ECM). A mandate would require simply that the devices be set — and new ones made tamper-resistant.

Those opposed to mandated speed limiters struggle to argue with the certain benefits they provide. For instance, opponents claim a mandate is inappropriate because there is no guarantee that drivers and motor carriers will not tamper with or otherwise disable them. But this argument follows the “let perfect be the enemy of good” approach. Had DOT used that logic in the past, we would not have benefited from the many safety systems in place today (e.g., seat belts) that have saved hundreds of thousands of lives.

It is indisputable that the vast majority of drivers and carriers would be compliant with a speed-limiter requirement and that it would generate substantial benefits, even if a small percentage of drivers and carriers did not comply.

Opponents also claim that speed limiters promote unsafe speed differentials between cars and trucks, and that requiring them will offset any safety benefits. However, the aforementioned FMCSA research refuted this assertion soundly by noting that domain research on the potential downside of speed deviations among vehicles that could occur because of the interaction of vehicles equipped with speed limiters and those without them seemed far outweighed by the significant safety benefits associated with the reduction in absolute speed afforded by speed limiters.

Given the certain benefits of speed limiters and the minimal cost of setting them, DOT should make this initiative a top priority. Speeding is a more significant factor in truck crashes than any other. As such, it deserves a corresponding degree of attention and certainly more than other DOT initiatives with benefits that are less certain or substantial.

American Trucking Associations, the largest national trade federation for the trucking industry, has headquarters in Arlington, Va., and affiliated associations in every state. ATA owns Transport Topics Publishing Group.