NHTSA Finally Tackles Rear Underride

One Ms. Marianne Karth of the Truck Safety Coalition and 11,000 signatories have succeeded where the Insurance Institute for Highway Safety – with all its fancy-pants testing – and the Canadians – with their much tougher standard – had failed, persuading the National Highway Traffic Safety Administration to initiate a rulemaking to upgrade the rear underride standard.

Earlier this month, the agency published a notice in the Federal Register announcing that it would issue two separate notices – an Advance Notice of Proposed Rulemaking on rear impact

guards and other safety strategies for single-unit trucks, and an NPRM on rear impact guards on trailers and semitrailers. Apparently, it was a May 5 meeting between the Coalition and Secretary of Transportation Anthony Foxx that turned the tide. The advocacy group presented their signatures and made the case that amendments to FMVSS No. 223, Rear Impact Guards, and FMVSS No. 224, Rear Impact Protection were long overdue.

IIHS got the typical cold shoulder NHTSA presents to outside suggestions. The announcement made no mention of the 2011 petition the IIHS submitted to “require stronger underride guards that will remain in place during a crash and to mandate guards for more large trucks and trailers.”  Spokesman Russ Rader says that the agency neither denied it, nor issued any official response.

“They told us they were working on it,” he says. “We’re glad that NHTSA is working to move forward in taking this first step.”

Three years ago, the IIHS didn’t gather signatures, but it did present lots of data to the data-driven agency. The Institute examined crash patterns leading to rear underride of heavy trucks and semi-trailers with and without guards, using the Large Truck Crash Causation Study, a federal database of roughly 1,000 real-world crashes in 2001-03.  It found that underride was a common outcome of the 115 crashes involving a passenger vehicle striking the back of a heavy truck or semi-trailer. Only 22 percent of the crashes didn’t involve underride or had only negligible underride, which they indicated was consistent with prior studies.  The study noted that “In 23 of the 28 cases in which someone in the passenger vehicle died, there was severe or catastrophic underride damage, meaning the entire front end or more of the vehicle slid beneath the truck.”

IIHS also performed a series of crash tests to assess the efficacy of various underride guards under different crash speeds and configurations (head-on and off-set) to determine what types of failures occurred.  The IIHS used the Chevy Malibu, a sedan with a high crash-test rating, as the bullet vehicle and trailers that were certified to Canadian and U.S. requirements as the targets.  Canadian requirements, required since 2007, are more stringent than the U.S. for strength and energy absorption.  In general the testing found significant performance differences between U.S. and Canadian guards – the Canadian guards performed significantly better.  The testing also revealed fundamental weaknesses in the attachments which don’t have to be tested as a whole system. 

In addition, IIHS pointed out that there were significant regulatory gaps allowing some heavy trucks to forgo guards altogether and if they are on trucks exempt from the regulations, the guards don’t have to meet 1996 rules for strength or energy absorption.

That petition followed a NHTSA November 2010 study showing that the guards were not very effective in preventing fatalities or serious injuries from rear impacts to tractor trailers. The study, conducted as part of the agency’s evaluation of Federal Motor Vehicle Safety Standards 223 and 224, used state crash data from Florida and North Carolina, showing a slight – not statistically significant – decrease in fatalities and serious injuries to occupants in a rear-impact crash with a tractor trailer. The agency noted, however, that the sample size might have been too small.

Rear guard protection has been a federal requirement since 1952, when the Bureau of Motor Carriers of the Interstate Commerce Commission required heavy trucks, trailers, and semitrailers to be equipped with a rear-end protection device designed to help prevent underride. The regulation contained no specifics as to the device’s efficacy, but merely required the guard to be “substantially constructed and firmly attached.”  In 1967, the Federal Highway Administration, attempted to begin a rulemaking to require a rear underride guard for trucks, buses and trailers, but industry fought off any substantive upgrade to the regulations for 44 years. In 1996, NHTSA published a final rule establishing two Federal Motor Vehicle Safety Standards (FMVSS) – 223, Rear Impact Guards, and 224, Rear Impact Protection. FMVSS 223, the equipment standard, specified strength requirements and compliance procedures for rear impact guards on semitrailers. FMVSS 224, the vehicle standard, specified mounting instructions and location specifications for those guards.

The agency has done little to improve the rule since.

The IIHS, which has been advocating for a better rear underride standard for decades, has launched a series of research projects that have ranged from determining the scope of the problem to developing a new underride guard. Last March, the Institute published the results of its latest round of testing

The IIHS has continued its research into effective underride prevention. In 2013, the Institute published the results of further testing it performed –also using a 2010 Malibu as the bullet vehicle, striking a parked truck at 35 mph in three overlap modes: 100 percent, 50 percent and 30 percent.

All eight guards successfully prevented underride, including one from Hyundai Translead, whose earlier model failed a full-width test by IIHS. In the second test, in which only half the width of the car overlapped with the trailer, all but one trailer passed. However, when the overlap was reduced to 30 percent, every trailer except one from the Canadian manufacturer Manac failed. Manac sells dry van trailers in the U.S. under the name Trailmobile. The Institute uses a 30 percent overlap for the most challenging underride test because it is the minimum overlap under which a passenger vehicle occupant's head is likely to strike a trailer if an underride guard fails.


“We’ve been told that five of the major trailer manufacturers have upgrades in the works that they are doing voluntarily, and we are hoping to test those upgrades as soon as they are available late this year or early next year,” Rader says. “Manufacturers have indicated the changes they made were not expensive and did not add a substantial amount of weight. It’s not a difficult task to make guards tougher.”