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Status Report, Vol. 45, No. 8 | August 21, 2010 Subscribe

Speed limiters in trucks would serve 2 purposes

President Obama's push to improve the fuel efficiency of large trucks could give new life to a safety initiative that has been stuck in the federal bureaucracy for nearly 4 years. In 2006, the American Trucking Associations and Road Safe America separately petitioned federal regulators to require speed limiters in trucks with gross weights exceeding 26,000 pounds. The petitions call for the devices, also known as speed governors, to be set at a maximum of 68 mph.

"This was a good idea 4 years ago, and it's arguably an even better idea today amid heightened concern about fuel efficiency," says Anne McCartt, Institute senior vice president for research. "With the technology widely available, this is an easy way to achieve safer truck speeds and reduce fuel consumption."

In May, Obama directed his administration to create a national policy to both improve the fuel efficiency of medium- and heavy-duty trucks and reduce their greenhouse gas emissions. This put the idea of speed limiters in a new light because every 1 mph reduction in large truck speed is estimated to yield fuel savings approaching 1 percent.

The National Highway Traffic Safety Administration (NHTSA) and Federal Motor Carrier Safety Administration solicited comments on the speed limiter petitions in January 2007. The Institute was one of many organizations voicing support (see "Institute supports speed limiters as big rigs’ interstate speeds rise," June 15, 2007), believing limiters set to 68 mph would improve safety though a greater benefit could be reaped with an even lower setting.

Why they're needed

More than 4,000 people died in large truck crashes in 2008. Only about 15 percent of them were truck occupants, and the rest were occupants of passenger vehicles, motorcyclists, or pedestrians.

High travel speeds increase truck stopping distances, which already are much longer than those of cars. For example, a large truck going 75 mph takes approximately one-third longer to stop compared with one going 65. Speed also exacerbates the size and weight differences between large trucks and passenger vehicles, leading to more severe crashes.

The European Union, Australia, and Japan, among other countries, already require speed governors in large trucks. So do the Canadian provinces of Ontario and Quebec. Despite the strong safety argument for requiring governors in trucks on U.S. roads, too, the government so far has failed to act. NHTSA says it's still analyzing this issue after drawing more than 3,800 public comments.

Among U.S. drivers, the concept has broad support. A 2007 Institute survey found 64 percent in favor of a truck speed governor requirement. Three of 4 in favor said they want the devices set at a maximum speed that's slower than 70 mph. But not all of the trucking industry embraces limiters. The Owner-Operator Independent Drivers Association, for example, has been among the most vocal opponents.

Some companies already use speed limiters

Most trucks have the basic technology. Since the mid-1990s, electronic control modules that, among other functions, can be programmed to limit speed have been standard equipment in trucks. Typically, the top speed is programmed in the factory according to buyer specifications, and many trucking companies already are programming to 68 mph or slower. ABF Freight System Inc. is one. It estimates that at a maximum speed of 62 mph, each truck emits 33.5 fewer tons of carbon dioxide annually, compared with an identical truck going 68 mph. The company also credits slower speeds with strengthening safety performance, though the exact benefit is impossible to calculate.

If speed limiters were mandatory, some steps would be needed to prevent truck owners from making unauthorized modifications to the control modules. To calculate speeds, the modules rely on fixed information such as tire size and transmission and rear axle gear ratios. Currently, owners can enter changes if they modify these parts of the truck, according to the Truck Manufacturers Association. This group has provided NHTSA with information on possible ways to resolve the issue.

Easy way to conserve fuel

When it comes to improving fuel efficiency, requiring speed limiters is "low-hanging fruit," Tom Hodgson, executive director of Road Safe America, recently told NHTSA. The agency has been tasked with developing efficiency and emissions standards for trucks beginning with the 2014 model year.

"The original rationale behind the petition was safety, but if fuel economy and pollution abatement are deemed as more important and can get this petition approved, so be it," Hodgson said in a comment filed with NHTSA on June 23.

This wouldn't be the first time fuel economy considerations led to slower travel speeds and associated safety benefits. The 55 mph national maximum speed limit, enacted in 1974, was a response to oil shortages. A decade later, the National Research Council found that this law, which required states to adopt 55 as a condition for receiving federal highway funds, was saving 2,000 to 4,000 lives per year (see "Council recommends Congress retain 55 mph limit," December 22, 1984). But after concerns about oil prices faded, Congress in 1987 allowed states to increase posted limits on rural interstates to 65 mph. Complete control over speed limits was returned to the states in 1995.

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