MISSISSAUGA, Ont. – Pity the poor Honda Civic.

That was the car Transport Canada researchers jammed under trailer underride guards to prove that existing U.S. designs can’t protect sub-compact cars. But through this summer’s crash tests, the researchers have also concluded that guards hanging closer to the ground aren’t the solution, either. It appears that it’s more important to have stronger designs that can hold back Canada’s ever-popular sub-compact cars in the event of an accident.

Nobody was more surprised than the researchers.

The crash tests were largely meant to prove a Transport Canada position that the U.S. designs had to be lowered if they had any hope of protecting smaller cars. The U.S. designs – required south of the border on trailers and semi-trailers built after January 1998 – hang 560 mm from the road.

(The U.S. guards are also required on 53-foot trailers and B-trains in Ontario and Quebec. While Canadian tankers loaded with dangerous goods have to have rear impact protection, it’s really meant to protect valves.)

Transport Canada obviously wants to require such guards across the nation, but it wants a better design before it lays down the law.

Federal regulators have for the past two years suggested that underride guards should hang 480 mm from the road. That had groups such as the Canadian Transportation Equipment Association complaining that the bars would catch on everything from steep loading ramps to uneven railway crossings.

However, Civics used in the crash tests were still able to slide under the lowered barriers because their bumpers sit just 400 mm off the ground and drop another 25 mm when the cars begin to brake.

Even Transport Canada officials admit that still-lower heights for the guards aren’t practical.

“Everybody should be driving Lincoln Navigators,” Transport Canada senior engineer Denis Boucher quipped during a presentation to the Canadian Transportation Equipment Association (CTEA), referring to the higher bumpers that come with the pricey sports utility vehicle. “But if you increase the stiffness of your guard, you get some good results … it is possible to have a guard with a ground clearance of 560 (mm) that will still protect a small car,” he said.

The CTEA has developed a generic design for underride guards to meet U.S. requirements, and it’s met wide acceptance since any repaired guards have to be certified to meet a pre-specified standard for strength. Only certain shops have been able to do the work, and U.S. trial lawyers would salivate at the thought of a below-standard guard that was involved in an accident.

The middle ground could be a uniquely Canadian guard that has to be stronger than its U.S. counterpart and maintains a 560-mm height after it’s hit with a pre-specified force. The U.S. requirements are linked to pre-impact heights.

The guard might have to be installed 500 or 510 mm from the road, just to account for its upper movement during a crash, suggested Daniel Davis, also of Transport Canada’s Road Safety and Motor Vehicle Regulation Directorate.

That’s not to suggest that the U.S. designs are useless. The Canadian research has found that they do keep larger vehicles such as Ford Windstar minivans from crushing through to trailer bogies.

The Chevy Cavalier, used as a benchmark mid-sized car, slid under the 560-mm guard built to the minimum U.S. standard for strength. That same car was held back by a lower guard during a low-speed crash, but still crushed through a 480-mm design when traveling at 65 km-h. When the 480-mm guard was strengthened, the passenger compartment was protected.

It’s important to improve the guards, to protect those riding in compact and sub-compact cars, since they account for about one in every three light-duty vehicles registered in Canada, the researchers suggest.

The occupants of sub-compact cars face an above-average risk of being injured in crashes that involve the rear ends of trailers. While they represent 11 per cent of the vehicles on the road, they account for 22 per cent of the fatalities in such accidents.

Of 3,000 on-road fatalities caused in 1995, 23 were linked to collisions with the rear ends of trailers, and 15 of those trailers had underride guards, Davis said. Ten of the fatalities involved crushed passenger compartments.

In all, about 300 injuries per year are caused by collisions with the rear ends of tractor-trailers.

“Hopefully we’ll have regulations on the streets pretty soon,” added Davis. In fact, internal pressure within the halls of Transport Canada is calling for a decision by December, he said.

The U.S. guard would cost about $150, while a unique-but-better Canadian guard would cost $180, Davis said, noting that the pricing wouldn’t be that expensive. “For only $30, this is the difference you’re going to get,” he said, referring to the remains of a car crunched under the underride.

Trailers, however, could be subjected to more damage if stronger underride guards are installed. “If it’s very stiff, your frame in the trailer will take a beating,” Boucher admitted.

Said researcher John Billing, who designed the stronger mounting for guards used in the tests, “a fair amount of rear end trailer damage will result when it hits a dock” if a guard is made stronger.

Even if Transport Canada requires a different design, the U.S. equipment is still expected to be allowed into Canada unless the provinces say otherwise, Boucher said. Al Tucker of the CTEA suggested “they wouldn’t go there”.

The data has left members of his association scrambling, since they have been involved in designing a generic bumper that is even gaining acceptance south of the border.

Regardless of which approach is taken, it’s likely that Canada will have rules of its own, Davis said.

“How can we say after we’ve done all this research that we want to harmonize?” n