Automotive Fuel Economy How Far Can We Go? (1992) / Chapter Skim
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3 SAFETY IMPLICATIONS OF FUEL ECONOMY MEASURES
3 SAFETY IMPLICATIONS OF FUEL ECONOMY MEASURES
Pages 47-68
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From page 47... ...
Many factors have contributed to this trend of reduced fatality rates in the past and are likely to affect future rates. They include support for stricter law enforcement and penalties for driving while intoxicated, increased use of safety belts and increased availability of passive protection, greater urbanization, a lower proportion of very young drivers, reduced motorcycle usage, and continued improvement in the highway environment.
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From page 48... ...
* Against the background of improving safety there is the question of the impact of changes in the weight and external size of passenger cars and light trucks and in the vehicle fleet mix.
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From page 49... ...
The ratio of these two factors provides an approximate index of rollover stability, although the dynamic characteristics of the suspension and handling also have a major influence. Light trucks and vans are less stable than passenger cars because, for a given track width, their center of gravity is higher.
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From page 50... ...
However, as will be discussed subsequently, from an overall societal viewpoint, changes in the weight TABLE 3-] Occupant Fatalities in Passenger Vehicles by Vehicle Type, 1990 Fatal Accident Reporting System Single Vehicle Vehicle TypeVehicle/Vehicle Non-Rollover Rollover Total Passenger cars Vansb Pickup trucks Utility vehiclesb Total 13,406a 587 2,333 382 16,708 (51.2%)
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From page 51... ...
Among other changes, the average weight and external size of the U.S. fleet moved toward that in other motorized countries.5 A variety of studies have concluded that the occupants 3The pickup truck's high rigid bumpers, often exacerbated by after-market modifications, are particularly hostile to occupants of passenger cars.
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From page 52... ...
Nonetheless, analyses of historical crash data provide some guidance on the point. Past Studies Most past analyses have focused on passenger cars.
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From page 53... ...
in a car population increases if any car in the population is replaced by a lighter one or if one population of identical cars is replaced by another population of lighter identical cars. Other studies have analyzed overall occupant fatality rates in relation to number of registered vehicles (Ford Motor Company, 1991; ITHS, 1987, 199ib)
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From page 54... ...
Evans and Frick used the relative risk of driver fatality ~ two-car collisions, while Ford and IIHS considered the occupant fatality rates per 10,000 registered vehicles. Evans and Frick used very broad ranges for vehicle model years and included much older vehicles; Ford and IIHS considered only more recent models and used much narrower vehicle age ranges.
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From page 55... ...
The use of the PARS data limits analyses to the extreme end of the injury distribution -- motor vehicle crashes that result in the death of at least one participant. It is well established that fatal crashes are not representative of the entire spectrum of crashes and do not necessarily provide a valid basis for broad generalizations about crash characteristics.9 9For example, alcohol consumption is much more likely to be a factor in fatal crashes, somewhat less so in injury crashes, and much less so in crashes resulting in property damage only.
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From page 56... ...
are based on the assumption that, for purposes of estimating vehicle exposure to accidents, one can use the distribution of vehicle weights for those vehicles involved in pedestrian fatalities. Yet this measure of exposure requires the assumption that vehicles involved in pedestrian fatalities are representative of the distribution of the exposure of the entire vehicle fleet.
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From page 57... ...
These analyses do not consider other types of crashes -- single vehicle into roadside obstacles, passenger car-truck collisions, and collisions of cars and light trucks with pedestrians and cyclists.33 Moreover, additional analyses are needed, based on more recent mode! years and actual data, to reflect improved vehicle design and increased use of occupant restraint systems.
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From page 58... ...
Because they have become such a significant portion of the passenger-vehicle fleet, more aggressive efforts to improve the safety and fuel economy of light trucks should be taken. Otherwise, any gains made through improvements in passenger cars may be offset by the increased use of light trucks.
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From page 59... ...
These anticipated weight increases apply to safety improvements only; they do not take into consideration any weight increases associated with technology required for improved emissions control (Bischoff, 1991~. The National Highway Traffic Safety Administration has issued a notice of proposed rulemaking to address the rollover stability of passenger cars and light trucks (Federal Register, 1992~.
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From page 60... ...
Indeed, because discretionary driving often presents the greatest risk, reduction in VMT may offer disproportionate safety benefits (Transportation Research Board, 1984~. However, it should be noted that in the United States, efforts to reduce VMT have been singularly unsuccessful -- VMT has increased more rapidly than the population of licensed drivers (Highway Statistics, 1987-1990~.
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From page 61... ...
Traditionally it has been assumed that "safety does not sell," but recent trends in consumer preference for passenger cars with airbags and for vehicles with good safety records suggest a major shift in the public's concern for safety. Yet the fact remains that the highway transportation system was developed primarily for purposes of mobility, not safety.
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From page 62... ...
· Numerous studies conducted over the past 30 years show there is a relationship between reduced vehicle size/weight and increased occupant fatality risk, but the difference in safety between large and small cars for recent model years has diminished. Significant improvements have been made in small and large cars, although proportionately greater improvement has been made in small cars, a result that might be anticipated seven that small cars had considerahiv more mom for improvement.
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From page 63... ...
interpretation of existing and projected data, a comprehensive study of the effects of vehicle weight and size on safety should be conducted and should examine the full range of crash severity and crash types. While such a study will not provide definitive answers regarding the future safety performance of the vehicle fleet, it should be valuable in clarifying the dimensions of the safety aspects of measures to improve fuel economy in automobiles and light trucks.
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From page 64... ...
Washington, D.C.: National Highway Traffic Safety Administration. Chelimsky, E
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From page 65... ...
1989. Analysis of Frontal Crash Safety Performance of Passenger Cars, Light Trucks and Vans and An Outline of Future Research Requirements.
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From page 66... ...
Occupant fatalities by passenger cars, vans, light trucks, and utility vehicles, by crash Wpe -- single and multi-vehicle, rollover and non-rollover. Washington, D.C.
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From page 67... ...
89-2B-0-005. Washington, D.C.: National Highway Traffic Safety Administration.
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From page 68... ...
68 Zador, P., J Bosomy Id ~ arts.
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