Sudden impact

Jan. 1, 2004
A CANADIAN REGULATION scheduled for publication early in 2004 is expected to affect U S and Canadian trailer manufacturers. The forthcoming rule, which

A CANADIAN REGULATION scheduled for publication early in 2004 is expected to affect U S and Canadian trailer manufacturers.

The forthcoming rule, which will address underride guards for truck trailers, will be more demanding than the current regulations that have been in effect on U S trailers since 1998, John Billing said at the Canadian Transportation Equipment Association's 40th Manufacturers Conference in Surrey, British Columbia. Billing is a senior research officer with National Research Council Canada.

One impact already being felt: Research conducted by Transport Canada that was used as a basis for its underride rulemaking. In researching its regulation, Transport Canada crashed a series of cars into rigid rear impact guards and into guards that minimally complied with FMVSS 223. The conclusion: that guards designed simply to meet FMVSS 223 are not strong enough.

The United States' National Highway Traffic Safety Administration is now planning its own research to evaluate the safety implications of current U S underride regulation. NHTSA is scheduled this year to begin collecting police reports of accidents involving car-truck rear end collisions. The report is due to be completed late in 2006.

“Transport Canada concluded that a much stronger guard was needed,” Billing said. “The NHTSA study likely will find many cases where there was significant intrusion into the car's passenger compartment, confirming Transport Canada's crash test findings that FMVSS 223 guards are not strong enough.”

The dual U S standards for rear underride (FMVSS 223/224) apply to Canadian trailers operating in the United States.

Transport Canada published a proposed version of its underride regulation (CMVSS 223) in October 2002. Publication of the final rule, Billing said during the November meeting, “is expected soon.”

The proposed version of CMVSS 223 would replace the P3 test found in FMVSS 223 with one in which a force of 350 kN (78,652 pounds) is applied uniformly across the bumper for a displacement of 125 mm (five inches). The guard must absorb at least 20 kJ (176,991 inch-pounds) of energy when the force is applied and released. The force, derived from Transport Canada's crash tests, is very close to the 334 kN (75,000 pounds) proposed in NHTSA's original rulemaking of 1969 (, Billing said.

The proposed CMVSS 223 would prohibit the guard from being more than 560 mm (22 inches above the ground after the force is released), whereas FMVSS 223 only requires this before the force is applied.

“The Transport Canada staff are finalizing the regulatory text,” Billing said. “They have dealt with most of the comments they have received since the proposal was announced.”

Among the expected provisions:

  • If the guard proves sufficiently strong, it can be exempt from the energy-absorption requirement.

  • Asphalt trailers will be exempt.

  • If the rear-impact guard is a symmetrical design, only half the guard need be tested.

The regulation would take effect one year after publication of the final rule. For two years after the effective date of the regulation, applicable Canadian trailers (any trailer manufactured for sale in Canada, whether by a Canadian or U S manufacturer) could comply with either the U S or Canadian standard. After two years, trailers must comply with the Canadian standard.

“A guard complying with the proposed Canadian standard will almost certainly comply with the U S standard,” Billing said.

The new testing of underride guards promises to have a ripple effect in the courtroom.

“Some U S manufacturers may find they need to redesign their guards in light of the Transport Canada findings,” Billing said. “That's because you can only protect yourself against product liability if your design is current state of the art.”

Added Al Tucker, executive director of CTEA, “So far, the enforcement of underride regulations has been soft. But that won't help you in court.”

The National Research Council previously designed a generic underride guard that meets FMVSS 223 that the CTEA's trailer manufacturer members can use.

“New designs will be needed after CMVSS 223 is published and before it becomes effective,” Billing said.

Preliminary analysis has indicated that multiple designs of underride guard based on the CTEA generic design will be able to meet the more rigorous standards Transport Canada has proposed. One of the more interesting guards has its upright members mounted well ahead of the rear sill and slanting rearward. A brace, mounted near the rear sill, slants forward to form a “Y.” This design allows the bottom of the guard to be mounted the full 22 inches above the ground and remain within the 22-inch limit after the impact. That is because this design actually causes the horizontal member to move slightly downward during the crash.

“The three preliminary assessments that we tested should all work,” Billing said. “But they will need to be finalized by finite element analysis, qualified by tests, and documented for use. Each will automatically meet FMVSS 223.”

Designs so far have involved only steel guards.

“We will survey manufacturers to see if there is enough interest in a generic aluminum bumper,” Tucker said.

Participating in the program

Manufacturers can sign on for the CTEA generic underride program for $1,500. “If you build according to the specifications, you have a certifiable underride guard,” Tucker said.

Many of the organization's members are small manufacturers who could not afford the engineering expense involved in designing and testing required to comply with the U S regulation. The program, open to U S and Canadian manufacturers, currently has 30 participants.