The National Highway Traffic Safety Administration has issued a notice of proposed rulemaking (NPRM) that would require “more robust” rear impact guards on trailers and semitrailers. The stronger guards would remain effective at up to 35 mph compared to 30 mph for current guards (also known as underride guards and “ICC bumpers.”)

The higher speed would coincide with crash protection standards for passenger vehicles, which must protect occupants in frontal impacts at speeds up to 35 mph, NHTSA’s announcement said.

Most trailers and semitrailers are already required to have rear impact guards mounted on their rear ends to prevent smaller vehicles from plunging into and under them.

The change would affect Federal Motor Vehicle Safety Standards 223 and 224 that govern rear impact guards and rear impact protection, respectively, the agency said. NHTSA believes many new trailers sold in the United States already demonstrate compliance with the more stringent performance requirements under consideration.

NHTSA estimates that the annual incremental material and fuel cost would average $13 million to ensure that all applicable future trailers and semitrailers in the U.S. are built to the more rigorous standards.

“The proposed rulemaking continues the agency’s initiative to upgrade the standards for truck and trailer rear impact crash protection,” the announcement said. Earlier this year, NHTSA published an advance notice of proposed rulemaking on more stringent rear underride crash protection.

“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, NHTSA said. 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. 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.

Comments on today’s NPRM on trailer and semitrailer rear underride protection can be submitted to the docket up to 60 days after publication in the Federal Register. Click here to view the NPRM.