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Status Report, Vol. 44, No. 8 | September 17, 2009 Subscribe

Tractor-trailers get better brakes under new rule

Stopping distances for new tractor-trailers will be 30 percent shorter than current requirements under an amended brake rule the federal government issued in July. The move should help reduce the frequency and severity of crashes between large trucks and smaller vehicles since the stopping distance of a fully loaded tractor-trailer may be up to 3 times longer than today's cars.

The National Highway Traffic Safety Administration estimates that about 227 deaths and 300 serious injuries will be prevented each year once all rigs get outfitted. Thanks to advances in brake technology, the improved drum brakes and air disc brakes needed to reduce minimum stopping distances already are on the market.

Most new tractor-trailers will have to stop in no more than 250 feet from 60 mph when carrying a full load, compared with the current 355 feet, or about the length of a football field. In comparison, cars must stop within 216 feet when braking from 60 mph. Many cars stop within 120-130 feet.

Current stopping distance rules for big rigs have been in effect since 1995. The new rules take effect in August 2011 for 3-axle rigs with gross weight ratings of 59,600 pounds or less. These trucks make up about 80 percent of all tractor-trailers. Two-axle trucks and those with weight ratings above 59,600 pounds must meet the rule by August 2013. The standard won't apply to single-unit trucks, which still must stop within 310 feet when loaded and 335 feet when empty.

"This is a big win, especially for passenger vehicle occupants," says Anne McCartt, Institute senior vice president for research. "Once the new rules are in place we urge regulators to look at better brakes for other truck types, including straight trucks."

Deaths in crashes involving large trucks have been declining, but these vehicles still account for more than their share of highway deaths, based on the number of trucks on the road and the miles they travel. About 4,000 people died in crashes involving large trucks during 2008. Sixty-nine percent of these deaths were occupants of cars and other passenger vehicles, 15 percent were truck occupants, and 14 percent were pedestrians, bicyclists, or motorcyclists.

When large trucks and passenger vehicles collide, 98 percent of the deaths are people riding in the passenger vehicles. Large trucks were involved in 23 percent of the deaths of passenger vehicle occupants in crashes of 2 or more vehicles during 2008.

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