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Status Report, Vol. 36, No. 7 | July 28, 2001 Subscribe

More conspicuous trucks are less likely to be hit in side or rear

3M
Researchers analyzed the crash involvement of truck rigs with and without reflective treatments in various light conditions (dark-not-lighted, dark-lighted, dawn, dusk, and daylight), finding that retroreflective tape is most effective in dark conditions with no lighting.

Red and white retroreflective tape has significantly reduced impacts into the sides and rears of truck trailers. A new study from the National Highway Traffic Safety Administration (NHTSA) indicates these treatments are most effective on roadways that are dark and unlighted.

For the study, the Florida Highway Patrol and Pennsylvania State Police collected 1997-99 data on crashes involving tractor-trailers, noting whether or not retroreflective tape had been applied to enhance conspicuity. Crashes were grouped according to whether they might have been prevented by improved conspicuity or whether they couldn't possibly have been affected by the conspicuity treatment. The first group of collisions included, for example, those involving cars striking the sides of truck trailers. The second group of crashes included tractor-trailers that ran off the road or other vehicles crashing into the fronts of truck rigs.

Conspicuity-relevant crashes were compared among trailers with and without retroreflective tape. The researchers analyzed crash results for various conditions including dark-not-lighted, dark-lighted, dawn, dusk, and daylight. The tape is most effective in dark, unlighted conditions.

In Florida, the tape reduced crashes into the rears and sides of trailers by 37 percent in dark-not-lighted conditions, compared with trailers that hadn't been treated with retroreflective tape. In Pennsylvania, the reduction in crashes amounted to 44 percent.

While the original rule applied only to trailers manufactured after December 1, 1993, the conspicuity requirement was extended in 1999 to the entire on-road trailer fleet, effective June 1, 2001. Tractors made after July 1, 1997 also must be treated.

But an important gap remains. NHTSA doesn't require treatment for single-unit trucks (as opposed to tractor-trailers), pointing out that the single units are less frequently operated at night and they're involved in fewer fatal crashes — about 25 percent of fatal large truck crashes.

"Still, single-unit trucks are involved in about 45 percent of injury-producing large truck crashes," notes Institute senior researcher Elisa Braver. "The NHTSA study results should prompt the agency to examine whether to extend conspicuity requirements to single-unit trucks. There are nearly 5.8 million of them on the road, and a substantial number operate during hours of darkness."

Braver adds that improved rear underride guards also would help prevent injuries. "Retroreflective tape can prevent some crashes into the rears of single-unit trucks. But in the absence of adequate rear underride guards, there's still a major hazard to people riding in passenger vehicles that strike the rears of these trucks, many of which sit high off the ground." Improved underride guards were required on trailers in 1998, but they aren't yet required on single-unit trucks.

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