The U.S. Department of Transportation's National Highway Traffic Safety Administration has issued a notice of proposed rulemaking (NPRM) that focuses on upgrading the Federal motor vehicle safety standards (FMVSSs) that address underride protection in light-vehicle crashes into the rear of trailers and semitrailers. The proposed rulemaking continues the agency’s initiative to upgrade the standards for truck and trailer rear impact crash protection. Earlier this year, NHTSA published an advance notice of proposed rulemaking on rear underride crash protection and visibility conspicuity of single unit trucks.

“A key component of DOT’s safety mission is ensuring that trucking, an essential element in our transportation system, operates not just efficiently, but safely,” U.S. Transportation Secretary Anthony Foxx said. “Today’s proposal is another important step in that effort.”

Most trailers and semitrailers are already required to have bars, known as rear impact guards, hanging down from the back of the trailer to prevent underride. To enhance underride protection, NHTSA proposes to require more robust rear impact guards on trailers and semitrailers. These more robust guards will improve underride protection in higher speed crashes compared to current rear impact guards.

FMVSS No. 223 (Rear impact guards) and FMVSS No. 224 (Rear impact protection) together address rear underride protection in crashes into trailers and semitrailers. NHTSA estimates that many new trailers sold in the United States subject to FMVSS Nos. 223 and 224 demonstrate compliance with the more stringent performance requirements under consideration. NHTSA estimates, on average, that the annual incremental material and fuel cost would be $13 million to ensure that all applicable future trailers and semitrailers in the U.S. fleet will be built to the more rigorous standards.

“Robust trailer rear impact guards can significantly reduce the risk of death or injury to vehicle occupants in the event of a crash into the rear of a trailer or semitrailer,” said NHTSA Administrator Mark Rosekind. “We’re always looking at ways to safeguard the motoring public, and today’s announcement moves us forward in our mission.”

Rear underride crashes are those in which the front end of a vehicle impacts the rear of a generally larger vehicle, and slides under the rear-impacted vehicle. For example, underride may occur in collisions in which a small passenger vehicle crashes into the rear end of a large trailer and the bed and chassis of the impacted vehicle is higher than the hood of the impacting passenger vehicle.

In excessive underride crashes, there is passenger compartment intrusion (PCI) as the passenger vehicle underrides so far that the rear end of the struck vehicle enters the passenger compartment of the striking passenger vehicle. PCI can result in severe injuries and fatalities to occupants contacting the rear end of the struck vehicle. A rear impact guard prevents PCI when it engages the smaller striking vehicle and stops the vehicle from sliding too far under the struck vehicle’s bed and chassis.

The occupant crash protection features built into today’s passenger vehicles are able to provide high levels of occupant protection in 35 mph frontal crashes. This NPRM would require trailer and semitrailer guards to remain in place and prevent PCI in crashes of severities of up to 35 mph versus the current requirement of up to 30 mph.