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Transportation Safety

JOHN D. GRAHAM

Civilizing the Sport Utility Vehicle

We can reduce the health, safety, and environmental risks of light trucks without decreasing their advantages for consumers.

Now that the media craze about the Firestone-Ford tire and sport utility vehicle (SUV) controversy is winding down, it's time to take a broader and more patient look at the impact that the growing popularity of SUVs and other light trucks is having in the United States. The good news is that the U.S. consumer has found that light trucks, particularly the SUV, offer an unprecedented combination of size, comfort, and versatility. The same vehicle can be used to go to and from work, fulfill carpooling responsibilities, haul cargo or tow boats on recreational trips, and take older children to and from college. The bad news is that sales of light trucks, which also include passenger vans and pickup trucks, have increased so rapidly that regulators and vehicle manufacturers have not devoted adequate attention to the consequences for safety and environmental objectives. Before discussing solutions, two rather extreme positions on this issue must be dismissed.

One extreme view is that vehicle manufacturers should be permitted to sell whatever product consumers want to buy, without any consideration of the consequences for environmental protection or occupant safety. This position ignores the reality of health, safety, and environmental risks that are not controlled effectively in free markets. Agencies such as the Environmental Protection Agency and the National Highway Transportation Safety Administration (NHTSA) are in business precisely because the public demands greater protection against risk than is typically provided by market transactions.

Another extreme position is that the U.S. government should prohibit, restrict, or discourage light truck sales in an effort to revitalize consumer demand for small passenger cars. Citing the European consumer's continued interest in small passenger cars, advocates of this position argue that there is something perverse about the American consumer's interest in the SUV. But this position ignores the fact that European governments tax both vehicles and gasoline (up to $4 per gallon) for revenue-generating purposes, that geography and patterns of urban development in the United States are more suited to a transport system based on private vehicles that travel both short and long distances, that U.S. households are larger than European households, and that the typical American consumer can better afford expensive light trucks because of superior U.S. economic performance. Interestingly, a small but growing number of affluent European consumers are also buying SUVs, even though many urban European streets are typically much narrower than U.S. streets.

What is needed in the United States is a concerted multiyear effort by regulators and vehicle manufacturers to "civilize" light trucks. By civilize I mean that we need to reduce the adverse societal consequences of this class of vehicles without significantly reducing their utility to consumers. Some of this progress can be accomplished by voluntary cooperative efforts, some can be induced by creative use of incentive mechanisms, and some will require old-style command-and-control regulation. Success will require a mix of near-term and long-term policies, including a variety of targeted research programs. There are already models of success in this arena that can be built on in the years ahead.

Reducing rollover crashes

Light trucks improve safety in a variety of ways. Their extra size and mass offer greater protection to their occupants in single-vehicle crashes into fixed objects, in collisions with heavy trucks, and in collisions with other passenger vehicles. There are 20 percent fewer deaths when two SUVs collide than when two cars collide. There are, however, three important safety concerns about light trucks that have not been adequately addressed.

One concern, highlighted by the Firestone-Ford controversy, in which tire tread separation appears to have contributed to perhaps 100 fatal crashes, is the single-vehicle rollover crash. This type of crash deserves special consideration because it is more likely than other crash types to result in a fatality or serious injury to occupants. Rollovers account for 15 percent of the fatal crashes involving cars, 20 percent for vans, 25 percent for pickups, and 36 percent for SUVs. These percentages reflect both the extra safety provided by SUVs to occupants in nonrollover crashes as well as the greater tendency of SUVs to roll over. They also reflect the behaviors of the drivers of these different vehicle types.

Historically, there has been an inverse relationship between vehicle size and rollover probability. This pattern exists among passenger cars and among many light trucks, suggesting that consumers who purchase larger vehicles are lowering their risk of being involved in a rollover crash. Yet recent data suggest that some (though not all) SUVs and pickup trucks, including some of the larger ones, have an unexpectedly high rollover probability. A concerted research program is needed to determine the causes and solutions of the rollover problem in SUVs and pickup trucks. The Firestone controversy notwithstanding, tires do not appear to be the cause of most rollovers.

In recent legislation spurred by the Firestone-Ford fiasco, Congress gave NHTSA two years to develop and implement a new experimental rollover test that could be applied to new vehicles and used as a scientific basis for consumer information programs. The test would be dynamic in the sense that moving vehicles would be experimentally monitored in specified tests to determine their propensity to roll over. In favoring this dynamic testing, Congress expressed a lack of confidence in an alternative "static" system that simply compares vehicles based on the ratio of a vehicle's width to the height of its center of gravity. It will take more than two years for NHTSA to develop this test and validate it with real-world crash data, providing a science-based rating system to inform consumers about rollover risk.

In the long run, it may be appropriate for NHTSA to go beyond consumer information and develop a mandatory motor vehicle safety standard to reduce rollovers. Although engineering of vehicles, tires, and roads is important in rollovers, Congress has not done enough to encourage NHTSA to initiate an aggressive informational campaign to highlight the dominant role of driver behavior (inebriation, excessive speed and/or acceleration, and inattentiveness) in the causation of rollover as well as other crashes.

Curbing "aggressivity"

A second, more complex safety concern involves the "aggressivity" of light trucks in two-vehicle crashes. This term refers to the vehicle's size, weight, shape, and construction characteristics. Analyses of the ratio of driver deaths in one vehicle to driver deaths in its collision partner are revealing: In head-on crashes involving full-sized vans and cars, six drivers die in cars for every driver who dies in the vans. When cars are struck in the side by light trucks, these "aggressivity" ratios are very bad for occupants of cars. Although light trucks as a whole account for only about one-third of the passenger vehicles on the road, they are involved in crashes that account for about 60 percent of the occupant fatalities arising from two-vehicle fatal crashes.

When a light truck and a car collide, the occupants of the car suffer a disproportionate share of the injuries for at least three reasons. First, the average light truck is about 900 pounds heavier than the average passenger car. Second, light trucks tend to be designed with more stiffness than passenger cars (for example, the frame-rail designs of many light trucks are not as flexible as the unibody design usually used for cars). Finally, the geometry of many SUVs, aimed in part at providing a higher ride for SUV drivers, creates a mismatch in the structural load paths in head-on crashes and causes an SUV to override car door sills in side impacts. The location of the bumpers is not always the most important feature, because bumpers are largely ornamental in the light truck fleet and do not always play a major role in occupant protection. Research is needed to define the most important load-bearing members in the structures of different vehicles and devise standards to make sure that when vehicles collide, these load-bearing members in different vehicles will engage each other.

Congress and state legislatures should pass tax credits or other incentives that encourage consumers to purchase vehicles with innovative engines and fuels.

Although there are no quick fixes to the aggressivity problem, several observations can be made. It appears that adding vehicle mass and structure to small cars would do more for fleet-wide safety than would making light trucks smaller or lighter. Beefing up small cars is favored by safety experts in the insurance industry, even though there will be fuel economy compromises. Side-impact airbags, particularly those that offer head as well as lower-body protection, can also make a useful contribution to crash compatibility. In addition, vehicle manufacturers are already making changes to the geometry and structure of light trucks to improve the compatibility of these vehicles in collisions with cars, without reducing the consumer utility of SUVs. Finally, there also needs to be an inquiry into why station wagons have become virtually extinct. Station wagons can meet many of the needs of large families without the safety risks of SUVs. The lack of market interest in station wagons may be rooted in a regulatory perversity: Fuel economy regulators classify wagons as cars, not as light trucks. If vehicle manufacturers were instead permitted to count wagons as light trucks, they could simultaneously improve their fleet-wide fuel economy ratings for cars and light trucks. Automakers would then have an incentive to promote wagons more aggressively.

There is no way to eliminate the adverse safety effects of mismatches of vehicle masses, a problem that arises from basic laws of physics. Potential consumers of small cars, who now represent a small and declining share of new vehicle purchasers, need to be informed about the adverse safety implications of their choices. Providing this information to consumers will require a major change in the current safety ratings of new vehicles published by NHTSA and consumer groups. Currently, a vehicle's mass plays no role in the safety rating systems for new vehicles. The experimental crash tests used to inform safety ratings are often conducted with vehicles striking a fixed barrier that is immovable and impenetrable. This kind of fixed-barrier test downplays the safety advantages of larger vehicles, since even roadside objects struck by cars (guardrails, bushes, and trees) are somewhat penetrable or moveable. In rating vehicles on the basis of frontal crash tests, NHTSA says that because the test reflects a crash between two identical vehicles, only vehicles from the same weight class can be compared when examining frontal crash protection ratings.

Vision clearance

A third concern often voiced by motorists is that large SUVs make it impossible for drivers in smaller vehicles to see the traffic ahead of them or to see the traffic flow when a driver is pulling out of a side street onto a major thruway. There is also concern that some large SUVs are excessively wide for some passenger lanes, increasing the probability of collisions with other vehicles, cyclists, and pedestrians. Although the rapid growth in light truck sales has not been associated with an overall increase in collisions or traffic deaths in the United States, there is need for a concerted national research program to determine whether particular types of crashes have become more frequent or injurious because of the presence of light trucks. Indeed, Congress needs to make a much larger overall investment in light truck safety research. The Health Effects Institute, an industry-government partnership for environmental-health research that involves university-based researchers, provides a useful model for progress in the science and engineering of light truck safety.

Another promising process for developing voluntary safety standards was recently used to address concerns about the safety of side-impact airbags. Led by the Insurance Institute for Highway Safety, engineers from competing manufacturers and suppliers, with NHTSA specialists participating, informally developed a workable uniform standard to ensure the safety of side-impact airbags. If this voluntary standard works, it may prove to be a more expeditious model for solving future safety problems than the adversarial command-and-control process and could be applied to dealing with SUV safety concerns. The "stick" of a mandatory standard, however, needs to be there to stimulate the process.

Greener SUVs

The rapid growth in light truck sales is disturbing to environmental scientists, who are increasingly confident that carbon dioxide emissions from vehicles and other sources are contributing to global climate change. The transportation sector accounts for about 25 percent of U.S. carbon dioxide emissions, and the passenger vehicle contribution is predicted to grow rapidly in the years ahead, without policy reforms.

Compliance with the Kyoto Treaty on climate change would require U.S. carbon emissions to be reduced below 1990 levels. Given the rapid rate of U.S. economic growth in the 1990s and its dependence on fossil fuels, this is not economically realistic. New energy technologies on the production and conservation sides have been proposed and would help meet the Kyoto reduction schedule, but these technologies are unproven, their cost is not currently competitive, and their adoption is uncertain. Compliance with the Kyoto accord is also politically unrealistic on a global scale, unless rapidly developing countries such as China and India become meaningful participants. Still, U.S. policymakers can and should take modest steps to slow the rate of growth of carbon dioxide emissions and contribute to worldwide efforts to slow the rate of global climate change.

The amount of carbon dioxide emitted by a vehicle is directly related to the amount of gasoline used, because emission control systems that are effective in reducing smog and soot do not reduce carbon dioxide emissions. Light trucks are typically less fuel efficient than passenger cars. In addition, NHTSA's current fuel economy standards are set at 27.5 miles per gallon (mpg) for passenger cars and 20.7 mpg for light trucks. Taking both cars and light trucks into account, the average fuel economy of the U.S. new passenger vehicle fleet has actually declined in recent years to 23.8 mpg, the lowest national value since 1980; a trend that reflects rising consumer incomes, declining real gasoline prices (until very recently), and growing consumer interest in light trucks.

Some energy conservation advocates favor tighter fuel economy standards for all passenger vehicles, especially for light trucks. They argue that vehicle manufacturers are simply refusing to implement known cost-saving technologies that will save fuel. Yet history suggests that tighter fuel economy standards, allowing manufacturers freedom to decide how to comply, lead to smaller and lighter vehicles, with adverse consequences for both personal and fleetwide safety. The key flaw in current fuel economy rules is that they give the same credit to all measures that save an equal amount of fuel, even those measures that reduce safety. They also discourage vehicle manufacturers from implementing new safety technologies (such as additional structural support and side-impact airbags) that increase vehicle weight and thereby reduce fuel efficiency.

Many economists recommend higher taxes on gasoline, though perhaps not as high as the taxes in Europe. The idea of using economics to induce consumer interest in fuel economy is a good one that has some support. But it runs into stiff objections on grounds of fairness from people living in regions where long-distance travel is a necessary part of life. Good economics is not necessarily fair or feasible in the eyes of citizens and their elected officials from western states. Increased taxes on gasoline could also have negative consequences for the tourism industry, which is vital in many parts of the country. Currently, there is greater popular support for a reduction in the gasoline tax than for an increase in the tax.

A better idea is for Congress and state legislatures to pass tax credits or other incentives that encourage consumers to purchase vehicles with innovative engines and fuels. During the past decade, significant progress has been made in the engines/ fuels arena through a cooperative industry-government research program. In order to offset the initial cost of innovative engines/fuels, consumer incentive programs should be expanded to include hybrid vehicles that combine electric propulsion with a small gasoline or diesel engine, or advanced diesel engines coupled with use of ultralow-sulfur fuels. A consumer tax credit program in Arizona was designed to encourage purchases of vehicles that run on clean fuels. Although this program has many technical and fiscal problems, it does demonstrate that new car buyers can be influenced by tax credits.

Toyota and Honda have recently introduced hybrid cars for sale in the United States that can travel more than twice the distance on a gallon of fuel as the typical car. General Motors projects that it will be offering hybrids by 2003. The same technology can be used in light trucks. Ford has announced plans to introduce in 2003 an SUV using hybrid technology that can achieve 40 miles per gallon instead of the 23 miles per gallon achieved by the basic four-cylinder version of the Ford Escape SUV. Daimler-Chrylser also has a hybrid version of its Durango SUV under development. Toyota recently announced that it is planning to offer a full range of hybrid gasoline-electric vehicles, from tiny compacts to commercial trucks. For the truck market, Toyota is planning to introduce a diesel-electric hybrid.

Opposition to the diesel engine in the United States is spirited, often based on concerns that these engines contribute to smog and soot, pollutants that have been linked with cardiopulmonary problems and cancer. Yet the diesel engine can be much cleaner if used in conjunction with the low-sulfur fuels already in widespread use throughout Europe. Advanced diesel engine pollution control technology also promises sharp reductions in emissions of nitrogen oxides and particles, the precursors of smog and soot in the air. European environmental authorities are promoting the advanced diesel engine through tax and regulatory policies because the advanced diesel is 20 to 40 percent more fuel efficient than gasoline-powered engines, thus promising fuel cost savings as well as contributions to Europe's carbon-control commitments under the Kyoto Treaty. Audi is currently advertising one of its diesel-powered sedans in Europe with the claim that is environmentally superior. Policymakers in the United States, in California as well as in Washington, D.C., need to take a serious second look at the future of the advanced diesel engine in combination with low-sulfur fuel.

The virtue of these innovations in engines/fuels is that they can achieve large gains in fuel economy without reducing the size, mass, or safety of vehicles. Light trucks and cars with these new engines will cost more to build (at least in the short run because of low production volumes), but consumer tax credits can be used to minimize their cost disadvantage in the marketplace.

The concept of using consumer tax credits for motor vehicle policy already has significant national political support. For example, a clean fuels bill introduced by Sens. James Jeffords (R-Vt.) and Orrin Hatch (R-Utah) has attracted significant Democratic cosponsorship. The bill could readily be expanded to include credits for vehicles with hybrid engines or advanced diesels. Thus, there are grounds for believing that the incentive approach could generate bipartisan support.

Collaboration, not combat

The explosion of consumer interest in light trucks is not simply a passing fad engendered by clever advertising campaigns from Detroit and Japan. It reflects the U.S. consumer's desire for a large, comfortable passenger vehicle that can be used for a variety of purposes in daily life. Yet there are safety and environmental concerns about light trucks that have not been addressed adequately by regulators and vehicle manufacturers.

The federal government needs to set in motion a multiyear program of research, incentives, voluntary standards, and mandatory regulations aimed at managing the health, safety, and environmental risks of light trucks. The issues involved are technologically complex, involve tradeoffs between multiple social objectives, and will create complicated political problems for elected officials. Progress will not occur in a year or two, and policymakers and engineers will need to be persistent. Indeed, a successful program will require effective collaboration among federal agencies, state officials, nonprofit groups, and a variety of private-sector groups, as well as normally competing political interests. Such a program also needs to set clear ground rules to avoid uneven results because of competition among motor vehicle manufacturers, fuel companies, and related industries. Because several recent cooperative efforts have achieved important progress, there is reason for hope that our current slow-moving, adversarial process of regulation can be replaced by a fast-moving, incentive-based process that harnesses the scientific and competitive talents of the private sector.


John D. Graham (jgraham@hsph.harvard.edu) is director of the Harvard Center for Risk Analysis.