LTVs: `safer' at what cost?

We have all heard the statistics. In a collision between a passenger car and a sport utility vehicle (SIN), the occupants of the car are more likely to suffer death or serious injuries than the occupants of the sport utility vehicle.

We have also heard different explanations for the statistics and different conclusions based on them. After all, don't simple principles of physics dictate that a bigger, heavier vehicle will fare better in a collision with a smaller, lighter car? Can we have collision-compatible vehicles without all driving the same small car? Do we have to give up our large vehicles?

For more than 30 years, courts have recognized that automobile manufacturers have a legal duty to design and build crash-worthy vehicles.(1) Automakers have a responsibility to take reasonable steps to minimize injuries to occupants in foreseeable crashes. It follows that manufacturers must design vehicles that protect their occupants without jeopardizing the occupants of other vehicles in collisions.

More and more pickup trucks, vans, and SUVs are on the roads. These vehicles--collectively referred to as light trucks and vans or LTVs--were about 20 percent of the U.S. vehicle population in 1980. In 1996, 34 percent of registered light vehicles--all vehicles except heavy ones like buses, trucks, and ambulances--were LTVs. This number is certain to increase due to the popularity of LTVs.

Although LTVs account for only one-third of registered vehicles, collisions between LTVs and passenger cars account for over half the fatalities in crashes between light vehicles.(2) Four of five people who suffer fatal injuries in these collisions are in the cars. As the National Highway Traffic Safety Administration (NHTSA) has recognized, "These statistics suggest that LTVs and passenger cars are incompatible in traffic crashes and that LTVs are the more aggressive of the two vehicle classes."(3)

The agency compared fatal injury statistics for drivers of passenger cars and drivers of LTVs involved in these crashes. It found that in frontal collisions between a car and a sport utility vehicle, 5.6 car drivers were killed for every SIN driver killed; 5.4 car drivers were killed for every van (full-size and minivan) driver killed; and 3 car drivers were killed for every pickup truck driver killed.(4)

These statistics are worse for car drivers in side-impact collisions. Thirty of them are killed for every SUV driver killed where an SIN strikes the driver side of a car. For every fatally injured driver of a striking van, 13 car drivers are killed. For every fatally injured driver of a striking pickup, 25 car drivers are killed.

These numbers drop for side-impact collisions involving only passenger cars. About 7 drivers of struck cars die for every driver of a striking vehicle. The driver-fatality ratio is about even where a car strikes the driver side of an LTV.(5)

These statistics reinforce our common-sense view that bigger is better and, more important, safer. But aren't all vehicles aggressive to anyone unfortunate enough to be struck by one? Do we really expect vehicles that weigh several thousand pounds to be compatible with smaller vehicles?

The auto industry has been studying LTV "aggressivity" for some time. In 1972, a Renault Group safety engineer said that considerations of aggressiveness had been recently introduced to the field of automotive safety engineering. He recognized the new perspective of "taking account of all the people involved in an accident; not just those in one of the vehicles."(6) A paper published by the Society of Automotive Engineers in 1971 examined the "small-versus-larger-vehicle collision-injury problem."(7)

Calspan Field Services, Inc., which works with NHTSA and other agencies on automotive safety research and accident investigation, published a study of light truck aggressivity in 1984. The study, funded by the Motor Vehicle Manufacturers Association, was primarily a statistical one based on fatality and injury rates and occupant compartment intrusion. While specific measurements of intrusion into the occupant compartment were not known, researchers considered how often emergency equipment had to be used to remove drivers from crushed vehicles.

They noted that "passenger car drivers were significantly more likely to have required extrication when involved in fatal head-on collisions with light trucks than when involved in fatal head-on collisions with passenger cars."(8) The researchers concluded that "light trucks are more aggressive, on average, than passenger cars."

Why the difference?

Most researchers discuss incompatibility as a function of three considerations: vehicle mass (or weight), geometric design, and vehicle stiffness.

Vehicle mass. On average, LTVs are 900 pounds heavier than passenger cars.(9) The reasons for this disparity are too numerous to discuss here.

An engineering degree is not required to understand that weight matters in a collision and affects how the vehicles are damaged. Less weight, however, does not have to mean less protection. The 1998-99 Volkswagen New Beetle, for example, was named a "best pick" by the Insurance Institute for Highway Safety, a rating no other small car earned, showing that "small" does not mean "unsafe."(10)

That "small" does not have to mean "uncrashworthy" is especially true in collisions that occur at less than highway speeds. Conclusions from a 1971 study by the Institute of Transportation and Traffic Engineering at the University of California, Los Angeles, include the following:

   Properly restrained small car operators appear to have no serious impact
   deceleration handicap for head-on collisions with larger passenger vehicles
   through 30 mph and probably approaching 40 mph. In the range of 40 mph and
   above, the collapse distance ahead of the front seat location is not
   sufficient to prevent direct encroachment of the passenger compartment by
   the larger car; for equally matched vehicles this condition did not occur
   until speeds of 50 mph each [were] reached.(11)

General Motors Corp. (GM) researchers have observed that mass is not always the dominating aspect in this situation, illustrating "the confounding engineering difficulty of this issue."(12) They performed a study on the effect of side impacts by various vehicles on a 1997 Honda Accord. Despite the fact that a Ford Taurus was loaded 15 percent heavier than a Chevrolet S-10 pickup, the impact by the S-10 resulted in "comparatively higher" injury scores.(13) An internal study at Ford Motor Co. in 1998 found that collisions between cars and light trucks kill 1,000 more car occupants each year than can be explained by weight differences alone.(14)

Some assert that vehicle compatibility will occur only if drivers are forced to drive identical cars. They contend that everyone should be free to drive larger vehicles and that safety advocates want everyone to drive small cars and be equally vulnerable. This would be unacceptable to the American public, and the car companies know it.

However, mass is only one factor. If vehicle geometry and stiffness were made more compatible, the effects of any weight disparity could be reduced.

Geometric design. Federal regulations mandate that manufacturers take into account the likelihood of a vehicle being involved in front, rear, side, and rollover collisions when they design vehicles. That a vehicle will be involved in collisions of each type is foreseeable. In fact, manufacturers have used sophisticated statistical measures to predict the likelihood of those occurrences since the days of the Ford Pinto.

Whether they base auto designs on foreseeability, government regulations, or the likelihood that products liability suits will be filed against them (or some of each), manufacturers build crumple zones into vehicles. For instance, the front of a vehicle is designed to yield and crush in a controlled manner in a frontal collision to lengthen the duration of the crash and allow occupants to "ride down" the crash. If the vehicle did not crush, it would stop immediately upon impact, and the occupants, who continue to move forward, would absorb all the collision forces. The goal of crumple zones is to allow crushing vehicle components to absorb some of the collision energy, lessening the effects on occupants and keeping the occupant compartment intact.

The crumple zone cannot perform properly, however, when a car strikes or is struck by a much taller vehicle. If the taller vehicle's bumper and other energy-absorbing components are several inches above the passenger car's bumper, the car's components designed to crush will go under the taller vehicle.

In these underride collisions, the heavy structural components of the taller vehicle will strike the weaker pieces of the passenger car, such as the hood and windshield--components that were not designed to absorb energy or protect vehicle occupants. In side-impact collisions, overrides occur when the taller vehicle hits the car high on the door rather than on the lower sill, an area more likely to resist crush.

A 1970 Society of Automotive Engineers article examined override-underride collisions between pickup trucks and smaller cars. The article found that "trucks may easily override the structure of a lower profile vehicle with resultant massive deformation. If the front structure of the truck were lowered, the mass destruction associated with override could be mitigated."(15)

Another study from the early 1970s said that "the structure-overriding tendencies of larger vehicles in a particular collision were found to greatly influence the severity of exposure to injury for occupants of the smaller vehicle."(16)

The researchers concluded that "crush-resistant qualities of the passenger compartment can be improved by such procedure[s] as standardization of bumper heights and by providing vertically oriented frame crash guards at front and rear ends (within the body sheet metal) and by providing intrusion-resisting structures and designs to the passenger compartment doors and side panels."(17)

The recommendation almost 30 years ago that bumper heights be standardized is of particular interest. Federal regulations require that the height of bumpers on all passenger cars be within a specified range.(18) The benefits of uniformity are obvious, considering the need for the structural components of vehicles to "match" in a collision. Pickups, SUVs, and vans are not defined as passenger cars, however, and are not subject to the same regulation.

Without government regulation of LTV bumper heights, manufacturers produce vehicles with varying ride heights that are not compatible with the passenger cars they build. NHTSA researchers found that SUVs have the highest ride height, with an average rocker panel height--the area directly behind the front tires--of 390 millimeters (about 16 inches).(19) This is almost 200 millimeters (8 inches) higher than midsize cars, "a geometric incompatibility that would readily permit the SIN to override any side structure in a car and directly strike the car occupant."(20)

A 1986 NHTSA study found that light truck aggressivity in side impacts was dependent on the height of the truck's hood. The researchers studied 12 collisions and found that a lower hood profile on the trucks would haw, reduced the probability of serious injury to the occupant of the struck car from 97 percent to 11 percent.(21)

There are ways to make high-riding SINs more compatible with lower passenger cars. The Mercedes M-Class SUV features a bumper height equivalent to the height of Mercedes's passenger car bumpers. Still, the SUV has the same ground clearance as other sport utility vehicles.(22) The new Ford Excursion, the largest SIN on the market, has a "blocker beam" located behind and below the front bumper to prevent passenger cars from riding under it in frontal collisions.

Steps being taken by automakers to make SUVs safer suggest that there is no reason for geometric incompatibility. In May 1998, the New York Times quoted several car company executives on vehicle modifications. An unnamed Ford Motor Co. manager said that the manufacturer was redesigning the suspensions of its SUVs so they will ride several inches lower and be less likely to override car bumpers and other safety features. GM was reported to have been testing a prototype Suburban that also rides lower.

The Ford source said, "The more we can get the alignment with the bumpers and where the crash energies are absorbed, the more it helps the problem with large vehicles and small vehicles."(23)

The apparent ease with which these changes are being made shows that SUVs' excessively high ride height is unnecessary. It also shows that ride height was determined without considering the risks to occupants of smaller vehicles.

Vehicle stiffness. Stiffness has to do with the amount of force required to deform a vehicle. LTVs, with the exception of minivans, are stiffer than passenger cars. Light trucks and SUVs typically have a stiff frame-rail design as opposed to the softer unibody design of cars and most minivans.(24)

A good example of stiffness incompatibility is that of a Ford Taurus passenger car compared to a Ford Ranger light truck. A Ranger must be hit with three times as much force as a Taurus to cause 200 millimeters of deformation.(25) In a collision between the two, the Taurus and its occupants will absorb a disproportionate amount of the crash energy even though the vehicles have equivalent mass and ride heights. A study found that the aggressivity effects of light trucks are present even when vehicle weights are equivalent, "suggesting the influence of frontal structure stiffness in the light trucks."(26)

Some within the automobile manufacturing community say frontal stiffness is a product of government test requirements. If federal regulations measure vehicle safety in large part by how well a vehicle performs when it crashes into a concrete barrier, adding stiffness to the front end may improve that measure. As stated in an article by three GM engineers,

   The rigid barrier test, utilized in NHTSA's MVSS [Motor Vehicle Safety
   Standard] 208 and NCAP [New Car Assessment Program] protocols, creates a
   significant incentive for manufacturers to make vehicle front-end initial
   stiffness (the front 250 mm) as steep as possible. Initially stiff front
   ends improve occupant performance numbers in the U.S. consumer metric
   (NCAP) testing.(27)

Have the front ends of vehicles been made stiffer to improve these test numbers? A NHTSA study concluded--

   [T]his study examined 175 LTVs to answer two questions--(1) have LTVs
   become stiffer over the 14 years that NCAP has been testing these vehicles
   and (2) do stiffer LTVs do better in NCAP? From these data and the
   assumptions of these analyses, it is concluded that, on average, LTVs have
   become less stiff and, therefore, potentially less aggressive in
   vehicle-to-vehicle crashes, and the less stiff LTVs have [a] higher NCAP
   rating.(28)

Indeed, less stiff vehicles can provide occupant protection superior to that found in SUVs built on rigid-frame rails. The 1999 Mercedes M-Class SUV uses a unibody design and crumple zones designed to absorb crush energy. It has received an Insurance Institute for Highway Safety "best pick" rating for performance in 40-mph offset frontal-crash testing, scoring considerably better than the Dodge Durango, the Jeep Cherokee, and the Mitsubishi Montero.(29)

Stiffness incompatibility can be improved, even according to those in the industry. Neil Ressler, Ford's vice president for advanced vehicle technology, said, "There's a whole series of ways to make these vehicles softer. It's pointless to be defensive about the issue. It affects all of us."(30)

Proving a case

To our knowledge, no compatibility/ aggressivity cases have been tried to date, as this legal theory is in the early stages of development. When it is eventually brought, a products liability claim of vehicle aggressiveness will be a crashworthiness or enhanced injury claim. A plaintiff will have to prove that the vehicles involved in the collision were defective or unreasonably dangerous and that this defective condition made his or her injuries worse than if the defective condition had not been present. Crashworthiness claims can also be stated in terms of negligence.

Much of the evidence to show the dangerous propensities of LTVs is statistical. Various studies, including those discussed above, show that occupants of a passenger car are more at risk for death and serious injury when their vehicle is struck by an LTV rather than a passenger car. When explained by a qualified automotive engineer, the statistics can show a jury that LTVs are defective and that the short-sighted designs resulted in the defects.

Proof of a defect, though, is only part of the burden in a crashworthiness case. Counsel representing injured plaintiffs or the survivors of a crash victim must prove the injuries were caused by defective or negligently designed equipment. This burden is likely to vary from state to state, but generally, plaintiffs must show that "but for" the defect, they would not have sustained serious or fatal injuries. Whether required by a particular state law or not, in practice, plaintiffs must also show that a reasonable alternative design would have prevented the injuries.

Consider a head-on collision between an SUV and a small passenger car. Assume that differences in ride height cause the SUV to override the bumper and structural load path of the passenger car. This mismatch allows the front of the sport utility vehicle to intrude into the occupant space. Also assume that the man in the car's front passenger seat sustains a severe head injury. Does he have a case against the SUV's manufacturer?

What was the cause of the head injury? Did he strike the dashboard or the front of the SUV as it crashed through the windshield? Plaintiff lawyers have the burden of proving that "but for" the defect, the client would not have sustained this injury. An initial step in meeting that burden is learning precisely how the injury occurred.

Assuming counsel can show the man struck or was struck by the SIN, counsel must prove the specific injury would not have resulted but for the defects in the striking vehicle. The attorney must look at the overall collision and the occupant kinematics to see what injuries are expected.

For instance, if the delta V--the change in velocity of the struck vehicle--is 75 mph, the car passengers would likely suffer serious injuries or death regardless of the car's safety equipment. On the other hand, death and serious injury are less frequent in 20- to 30-mph delta V collisions, and a properly restrained passenger can emerge from these collisions without permanent injuries.

Injured passengers may have a case if their injuries were caused by contact with the SIN, if the overall collision energy was low enough that the injuries were not a probable outcome, and if the override and vehicle intrusion were caused by the SUV's unreasonably high ride height.

Given the difficulty of proving any crashworthiness case--especially an aggressivity case--it is important that the attorney preserve both vehicles involved in the collision. The case will hinge on whether the LTV's mass, geometry, or stiffness or a combination of these features defeated the safety features of the passenger car and enhanced the passengers' injuries.

To make this analysis, a qualified accident reconstructionist and mechanical engineer will need to evaluate the accident, including the vehicles' speeds, the direction of the forces in the accident, and the points of contact and intrusion. This analysis will require detailed inspection of both vehicles.

Once the facts can be determined and it is clear that the LTV compromised the survival space of the passenger car, a biomechanical expert will have to determine whether the intrusion of the LTV caused enhanced injury. This expert will have to decide whether the injury could have been prevented or significantly reduced if the intrusion had not occurred.

If this expert determines that the man would not have sustained the same or similar injuries had there been no significant intrusion, a mechanical engineer needs to determine whether reasonable alternative designs were available that could have prevented the LTV's intruding into the car's safety zone.

For example, would a blocker beam similar to that found on the Ford Excursion have prevented the injury? Would lowering the LTV's bumper have had that same effect? Would decreasing the stiffness of the LTV's front end have reduced the danger to those in the passenger car?

Defendants will argue that the collision was so violent that no matter what the reasonable alternative design, the car passengers would have suffered the same or similar injuries. This, of course, means that the accident reconstruction and the analysis by the mechanical and biomechanical engineers will be critical and must be completed at the earliest possible stage of the litigation.

Other factors, such as alcohol and seat belt use, are also important. We doubt that an aggressivity case is viable if the potential plaintiff was driving while intoxicated or if he or she did not wear a seat belt. There may be exceptions to these situations, but these are good guidelines.

Litigation in aggressivity cases is new, and it is important that the plaintiff's attorney be confident about the case. Preservation of the vehicles and early consultation with experts may bring justice for an injured client.

Notes

(1.) Larsen v. General Motors Corp., 391 E2d 495 (8th Cir. 1968); Frield v. General Motors Corp., 165 S.E.2d 734 (Ga. Ct. App. 1968).

(2.) Hampton C. Gabler & William T. Hollowell, NHTSA's Vehicle Aggressivity and Compatibility Research Program, Proceedings of the Sixteenth International Conference on Enhanced Safety of Vehicles, National Highway Traffic Safety Admin. Paper No. 98-S3-O-01, at 1 (June 1998).

(3.) Id.

(4.) HAMPTON C. GABLER & WILLIAM T. HOLLOWELL, THE AGGRESSIVITY OF LIGHT TRUCKS AND VANS IN TRAFFIC CRASHES (Soc'y of Automotive Engineers Paper No. 980908, 1998), available at http://www-nrd.nhtsa.dot.gov/nrd10/aggressivity/ documents/980908/980908.htm (visited Nov. 15, 1999).

(5.) Id.

(6.) Phillippe Ventre, Homogeneous Safety Amid Heterogeneous Car Population? Third International Technical Conference on Experimental Safety Vehicles 2-39 (1972).

(7.) DERWYN M. SEVERY ET AL., SMALLER VEHICLE VERSUS LARGER VEHICLE COLLISIONS 2929 (Soc'y of Automotive Engineers Paper No. 710861, 1971).

(8.) CALSPAN FIELD SERVS., STUDY OF LIGHT TRUCK AGGRESSIVITY 16 (No. PB85-125730, 1984).

(9.) Gabler & Hollowell, supra note 2, at 7.

(10.) Insurance Institute for Highway Safety, Crashworthiness Evaluations: Small Cars, http:// www.hwysafety.org/vehicle_ratings/ce/small_cars/ crashsmall.htm (visited Oct. 20, 1999).

(11.) SEVERY ET AL., supra note 7, at 2956.

(12.) DON VANDER LUGT ET AL., VEHICLE COMPATIBILITY --ANALYSIS OF THE FACTORS INFLUENCING SIDE IMPACT OCCUPANT INJURY 7 (Soc'y of Automotive Engineers Paper No. 1999-01-0067, 1999).

(13.) Id. at 7.

(14.) Keith Bradsher, Auto Makers Seek to Make Light Trucks Safer in Crashes, N.Y. TIMES, May 22, 1998, at D1.

(15.) MICHAEL R. APPLEBY ET AL., INJURIES IN UNDERRIDE-OVERRIDE COLLISIONS--A CLINICAL STUDY 8 (Soc'y of Automotive Engineers Paper No. 700483, 1970).

(16.) SEVERY ET AL., supra note 7, at 2929.

(17.) Id. at 2957.

(18.) 49 C.F.R. [sections] 581 (1999).

(19.) GABLER & HOLLOWELL, supra note 4. NHTSA has examined ride height at the rocker panel. The rocker panel is a substantial structural member, and measurement in this area sets the lower boundary for the frame structure.

(20.) Id. at 7.

(21.) M.W. MONK ET AL., STRIKING VEHICLE AGGRESSIVENESS FACTORS FOR SIDE IMPACTS 9 (National Highway Traffic Safety Admin. Paper No. NAD-52, 1986).

(22.) Bradsher, supra note 14.

(23.) Id.

(24.) See Gabler & Hollowell, supra note 2, at 7.

(25.) Id. at 8.

(26.) CALSPAN FIELD SERVS., supra note 8, at 46.

(27.) VANDER LUGT ET AL., supra note 12, at 9.

(28.) BRIAN T. PARK ET AL., THE NEW CAR ASSESSMENT PROGRAM: HAS IT LED TO STIFFER LIGHT TRUCKS AND VANS OVER THE YEARS? (Soc'y of Automotive Engineers Paper No. 1999-01-0064, 1999), available at http://www.nhtsa.dot.gov (visited Dec. 1, 1999).

(29.) Insurance Institute for Highway Safety, Crashworthiness Evaluations: Midsize Utility Vehicles, http://www.hwysafety.org/vehicle_ratings/ce/ mid_suvs/mid_suv.htm (visited Sept. 7, 1999).

(30.) Greg Gardner & Drew Winter, Fine-Tuning the Laws of Physics: Issues of Heavier Vehicles Hitting Lighter Ones Has Engineers in a Quandry, WARD'S AUTO WORLD, Apr. 1998, at 36.

Robert M.N. Palmer and William Petrus practice law in Springfield, Missouri.