IIHS Asks NHTSA for Stronger Underride Rule

This month, the Insurance Institute on Highway Safety reignited efforts to address the underride problem and petitioned the federal government to “require stronger underride guards that will remain in place during a crash and to mandate guards for more large trucks and trailers.”

The Institute based its latest effort on a study using the Large Truck Crash Causation Study, a federal database of roughly 1,000 real-world crashes in 2001-03.  The organization examined crash patterns leading to rear underride of heavy trucks and semi-trailers with and without guards and 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 determine which underride guards perform better than others and under various crash speeds and configurations (head-on and off-sett) to determine what types of failures occurred.  Testing was done using a highly crash-rated sedan, the Chevy Malibu, into trailers that were certified to Canadian and U.S. requirements.  Canadian requirements 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.

IIHS went on to note that a regulatory gaps exists that allow 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.  “Underride standards haven’t kept pace with improvements in passenger vehicle crashworthiness,” president of IIHS Adrian Lund said “Absent regulation, there’s little incentive for manufacturers to improve underride countermeasures, so we hope NHTSA will move quickly on our petition.”

The petition comes just as the agency was closing the comment period concerning an underride study it published in November, 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. The researchers also conceded that it was not possible to establish a nationwide downward trend in passenger vehicle fatalities in such crashes because the Fatality Analysis Reporting System does not list the model year of the trailer.

The request for comments drew little interest, with the majority of the responses coming from safety advocates – and the trucking industry associations remaining silent. The IIHS criticized the results of the NHTSA study as hampered by too many factors outside the researchers’ control to render the data reliable. (Where have we heard that before?)

“IIHS believes rear underride of large trucks remains a substantial problem. We are continuing our research in this area and encourage NHTSA to do the same. The agency’s technical report does not provide a valid comparison of guards built according to FMVSS 223 and 224 with those built to previous regulations. Furthermore, it is more important to evaluate the standards against a reasonable expectation of real-world performance than the 1953 rule with its nominal dimensional requirements,” Matthew Brumbelow, an IIHS senior research engineer wrote in a December letter to the agency.

Rear guard protection has been a federal requirement since 1952, when the Bureau of Motor Carriers of the Interstate Commerce Commission (ICC) established regulation 393.86 which 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, the precursor to NHTSA, 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, has long been active in advocating for a rear underride standard, researched various aspects of the issue, from determining the scope of the problem to developing a new underride guard. In 1977, it launched a program to develop a lightweight and effective guard that might serve as a prototype. Researchers designed and tested two guards and concluded that it was feasible toachieve substantial improvements in underride protection without significant increases in the weight of underride protection devices.

In 1998, a former NHTSA safety standards engineer underscored the inadequacy of the U.S. rules in a series of crash tests involving rear underride guards built to reflect the then-newly minted rear impact protection standard. The work by John E. Tomassoni showed that underride guard that minimally complied with the new rule were effective at impact speeds of 30 mph. But in some of the tests, the underride magnitude was such that passenger compartment intrusion (PCI) occurred – in some instances, the dummy head contacted the deformed occupant compartment. Tomassoni found many other weaknesses in the standard. For one, he used a vehicle frame height of 48 inches – “had the frame height been set at the lower typical trailer heights the PCI at a 30 mph impact speed would have been much greater.”

Tomassoni noted that the underride guard designed to meet the minimum static load requirements “will not provide adequate protection in offset impacts.” Finally, he noted the absence in the standard of allowable underride and recommended “that allowable underride be established to be not less than 12 inches to a laterally oriented vertical plane which passes through the center of the steering wheel whether PCI occurs or not.”

Canadian researchers have also tackled the underride issue. In 2002, Transport Canada conducted a series of tests using a 1998 Ford Windstar, a 1998 Chevrolet Cavalier, and a 1998 Honda Civic,  to verify the performance of rear impact guards built under FMVSS 223/224.  It found that “none of the minimally compliant guards were effective for all three vehicle types tested.” A 480mm (approximately 19-inch) guard with a displacement-limiting stopper provided good protection to the Cavalier and the Civic at several speeds. A 560mm (22 inches) stronger slanted guard provided good protection to the Civic at 48km/h. The authors recommend adding additional testing requirements to FMVSS 223 and adding additional guard requirements.

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