WINDSOR, Ontario - Defenders of the sport-utility owe a small debt to trucker Kenneth Murphy.
On the eve of an auto safety conference here last week, Murphy gridlocked a Detroit-area freeway nearby after crashing the 14-ton diesel excavator he was hauling into an overpass. The shovel toppled from its trailer and into the path of a Lincoln Navigator, a poster vehicle for critics of sport-utilities.
The Navigator's occupants, a mother and two children she was ferrying to their soccer game, survived the impact without life-threatening injuries.
Murphy's crash underscores the challenge facing automakers and safety regulators: How to make light trucks less menacing to other vehicles without compromising their own crashworthiness and without sacrificing the rugged image and function that have ignited their sales.
'To tamper with the kind of protection that (the Navigator owner) bought that vehicle for is something we don't want to do,' says Ernie Grush, a Ford Motor Co. safety analyst attending last week's conference.
The forum, the 16th Interna-tional Technical Conference on the Enhanced Safety of Vehicles, exposed the automakers' dilemma.
In simultaneously fighting a public relations problem and a technology problem, contradictions happen. The week saw earnest discussion of how to make trucks less harmful to cars. Yet, in the end, there were no promises -and heartfelt defenses of the status quo.
Nevertheless, engineers debate how to make cars and trucks coexist more harmoniously.
They focus on the three big factors in a collision: mass, chassis stiffness and chassis configuration.
Physical law dictates that vehicle mass wields the biggest bat of the three. In frontal impacts, a vehicle's mass alone determines 50 percent of the damage severity, while in side impacts, mass accounts for 65 to 90 percent, says Priya Prasad, a safety researcher with Ford.
'The lower-mass vehicle will always have the higher change in velocity in a crash,' says Prasad. Velocity change is what causes occupants to be thrown around in a vehicle in a frontal collision. (In contrast, victims in side-impact crashes are typically injured by the penetration of the striking vehicle).
'For a 2-1 weight ratio, the lighter car undergoes twice the velocity change,' Prasad says.
In NHTSA's tests, four 1997 Honda Accords weighing an average of 3,348 pounds were T-boned - one by a 3,641-pound Chevrolet S10 pickup, one by a 3,975-pound Chevy Lumina, one by a 4,562-pound Dodge Grand Caravan and one by a 4,670-pound Ford Explorer. The highest recorded injury values were in the Explorer's crash. (See story, Page 28.)
Weight reduction is an ongoing crusade in the auto industry, now complicated by America's taste for larger vehicles with more features.
Cheap fuel and the lower corporate average fuel economy standards for light trucks - 20.7 mpg, instead of 27.5 mpg for passenger cars - give automakers little incentive to divert from traditional mass-intensive body-on-frame configurations.
'CAN'T DISPUTE NEWTON'
Nial Wykes is one delegate who does not see mass reduction as a silver bullet. He is the manager of vehicle compatibility research for the Transport Research Laboratory in the United Kingdom, a former government agency that was privatized two years ago.
'You can't dispute Newton; mass will always play a role. But there's too much attention given to it,' says Wykes. He encourages automakers to take a closer look at stiffness and chassis configuration.
Truck frames are inherently rigid because they bear the entire load of the powertrain and suspension, allowing the body to be a relatively limp shell. The frame's height allows the longer suspension travel and clearance needed for off-road use.
But when there is a crash, the frame also acts as a battering ram, particularly as the typically elevated height causes it to plow into passenger cars above their chassis rails and side sills.
Wykes says lowering and redesigning the frame would better 'link' the energy-absorbing components in the two colliding vehicles. 'The fact that one vehicle overrides another in a crash means that it is not giving the smaller car an opportunity to use its energy-absorbing capabilities.'
According to Wykes and others at the conference, automakers could make truck frames more crash-friendly by:
Redesigning the front rails with flutes - rounded grooves - or other structural tweaks that collapse them in a predictable, controllable way.
Relocating the engine rearward to create room for a forward crush zone in the frame rails.
Adding a reinforced cross brace that extends several inches below the frame. As it penetrates a car body, it would meet up with the car's energy-absorbing rails.
Using the same cross brace to 'tie up' the truck's frame rails so that both sides of the frame collapse in an offset collision. Two frame rails would then take the force instead of one.
Reducing front and rear overhang so that the vehicle's ability to go off-road could be maintained with a lower frame.
Mounting the suspension to elevated subframes. The primary frame then could be lowered without sacrificing suspension travel.
Automakers have adopted some of these fixes already. David Degeneffe, a safety engineering manager for the GM Truck Group, notes, for example, that the front 6 inches of the frame rails in the new Silverado and Sierra pickups are made to telescope in a crash. So, overall, the truck retains its stiffness, but the very front of the front end is more crushable, he says.
TAKING THE NEXT STEP
But automakers largely have been reluctant to go further, citing a lack of hard data on compatibility and the need to improve passenger-car side-impact protection.
That 'offers a benefit whether you're getting hit by a truck, whether you're getting hit by another small car or whether you've ventured off-road and run sideways into a tree,' says Terrence Connolly, director of General Motors' safety center in Warren, Mich.
Ford's Grush insists the automakers' hands also are tied by federal regulations, including the government's own New Car Assessment Program. The NCAP crashes, which smash a vehicle into a rigid barrier at 35 mph and run a sled into the side of the vehicle at 38.5 mph, mean Ford must keep the truck frame very stiff, he says.
Passing the test is not required under Federal Motor Vehicle Safety Standard 208, which sets the injury threshold for an unbelted male at 30 mph. But the NCAP's five-star rating system is 'almost a de facto regulation' because of its influence on customer preference, Grush says.
Others disagree that NCAP precludes softer frames. 'That's nonsense,' says Brian O'Neill, president of the Insurance Institute for Highway Safety in Arlington, Va. The agency conducts its own barrier tests on vehicles - at 40 mph. O'Neill says vehicles with stiffer front ends tend to score worse in the tests.
'Mass is important in a crash, but there's a growing consensus that (chassis configuration) is very important, and stiffness is the least important of the three,' he says.
O'Neill says he believes the industry should study solutions that are even more unconventional, such as airbags that deploy outside the car.
Says O'Neill: 'To make a huge difference, we're going to need some radical new ideas.'