When a car runs into the back of a tractor-trailer outfitted with a weak underride guard, the outcome is too often deadly for people in the smaller vehicle. Backed by crash tests and studies of real-world underride cases, the Institute has outlined ways to improve rear guards to make them less likely to buckle or break off during a rear crash. Prompted by this research and tougher regulations in Canada, some trailer manufacturers have adopted better designs. Now U.S. regulators are poised to address the issue.
Three years after the Institute first petitioned federal regulators for tougher requirements and suggested specific improvements (see "Crash tests demonstrate the need for new underride guard standards," March 1, 2011), the National Highway Traffic Safety Administration (NHTSA) has initiated rulemaking to consider new standards for rear underride guards on trailers, semitrailers and single-unit straight trucks.
Underride guards are steel bars that hang from the backs of trailers to prevent the front of a passenger vehicle from moving underneath the trailer during a crash. When a passenger vehicle ends up under a large truck, the top of the occupant compartment gets crushed because the structures designed to absorb the energy of a crash are bypassed. The airbags and safety belts can't do their jobs, and people inside can experience life-threatening head and neck injuries.
Many trailer manufacturers already use stronger guards to comply with new regulations in place in Canada since 2007. Both North American standards require a guard to withstand a certain amount of force at various points. Under the Canadian regulation, a guard must withstand about twice as much force as the U.S. rule requires at the point where the guard attaches to its vertical support. IIHS tests in 2013 demonstrated that underride guards built to the Canadian standard generally work well to prevent underride, except in crashes occurring at the outer edges of trailers. The dramatic tests helped the Institute zero in on one design that raises the bar when it comes to safer truck underride guards (see "Not good enough," March 14, 2013).
NHTSA in a July notice in the Federal Register indicated it plans to issue two separate notices — an advanced notice of proposed rulemaking for single-unit trucks and a notice of proposed rulemaking for trailers and semitrailers.
The agency says it is responding to a petition by the Truck Safety Coalition and Marianne Karth, a North Carolina mother whose daughters AnnaLeah, 17, and Mary, 13, died in an underride crash in 2013. The sisters were on their way to Texas with their mother and brother for a family celebration when on a Georgia interstate a large truck hit their Crown Victoria, spinning it around and pushing it backwards into the rear of another tractor-trailer. AnnaLeah and Mary were seated in the back seat and received horrific injuries.
Surviving family members traveled to Washington, D.C., to present the "AnnaLeah and Mary Stand Up for Truck Safety" petition with more than 11,000 signatures to the U.S. Department of Transportation on May 5, marking the one-year anniversary of the crash.
Karth says the Institute "played an important part in our efforts. First of all, your research and reports enlightened us and then that led to us being enraged and asking the question, ‘If something could be done to make underride guards stronger, then why wasn't it being done?' That, of course, led to us being empowered to educate and motivate others to join with us in asking for change."
In its submission to NHTSA, the group references the Institute's petition, as well as the National Transportation Safety Board's recommendations for improving rear impact protection.
NHTSA hasn't officially responded to the Institute but gave a nod to its research in a footnote to the July grant of petition for rulemaking.
"We note that the Insurance Institute for Highway Safety and the National Transportation Safety Board requested some of the same amendments to rear impact guards as the Petitioners," the agency says in its Federal Register notice.
"IIHS research and crash tests helped lay the groundwork for an upgraded U.S. standard, and we are pleased to see NHTSA take action on the serious problem of rear underride crashes," says David Zuby, IIHS executive vice president and chief research officer.
In 2011, the Institute asked NHTSA to require rear underride guards that are strong enough to remain in place during a crash. The petition came after IIHS crash tests and research found that guards meeting federal safety standards can fail in relatively low-speed crashes. Researchers concluded that the current minimum strength and dimensions required for underride guards are inadequate. At the time, the Institute also asked NHTSA to broaden rules to consider applying the standards to other types of large trucks, such as single-unit straight trucks, that aren't required to have rear underride guards.
The Institute followed up its analysis by putting trailers from the eight largest manufacturers through a series of progressively tougher crash tests. All of the trailers had underride guards that met both U.S. and Canadian standards.
In each test, a 2010 Chevrolet Malibu struck a parked truck at 35 mph. In the first scenario, the car was aimed at the center of the trailer. All eight guards successfully prevented underride. In the second test, in which only half the width of the car overlapped with the trailer, all but one trailer passed.
The third test was the most challenging, and every trailer except one from Canadian manufacturer Manac failed. In the test, the Malibu struck the rear of the trailer at its outermost corner, engaging 30 percent of the car's width.
Manac's design was best in the group. The Institute noted that the supports of the Manac trailer's rear underride guard were attached to a reinforced floor and located closer to the trailer's outer edges than on other models. The design limited the potential for injuries to the dummy in the Malibu and also reduced damage to the trailer itself.
The Institute plans additional crash tests of recent model trailers from manufacturers that have indicated they are using better rear underride guards.
NHTSA says it is considering whether Manac's design should be the model for an upgraded standard. The Truck Safety Coalition-Karth petition requests that "all trucks and trailers should be required to be equipped with energy absorbing rear impact guards mounted 16 inches from the ground with vertical supports mounted 18 inches from the side edges." The petition doesn't name Manac but notes, "We are well aware of a trailer manufacturer which has gone beyond these standards and ‘raised the safety bar.'"
The group also asked NHTSA to require impact guards to address the problem of side underride and front override crashes. The agency said it is evaluating the latter request.
The U.S. government doesn't require tractor-trailers to have front or side underride guards. In Europe, front underride guards have been required on large trucks since 1994 to protect passenger vehicle occupants in crashes with combined speeds of about 35 mph. Europe also requires side guards to protect pedestrians and bicyclists but not people in passenger vehicles. The Institute has found that front and side underride guards have the potential to reduce injury risk.
In a 2012 IIHS study of fatal crashes between large trucks and passenger vehicles, an estimated 63 percent involved the front of a truck, 22 percent involved the side and 15 percent the rear. Analyses of smaller samples of fatal crashes found that 88 percent involving the side of the large truck and 82 percent involving the rear produced underride.