vehicle compatibility problems may pose a major challenge to lightweight vehicle safety design. A
concern here was that current barrier tests might force even the heaviest vehicles to have stiff
front ends, making them quite dangerous. to all of the other, lighter vehicles on the road. Thus far,
however, NHTSA has found that application of the barrier tests to heavier vehicles--such as full-
size pickups and vans, as well as heavy luxury cars--has tended to force them to soften their front
ends, making them less aggressive to other vehicles.^96 Nevertheless, NHTSA might want to take
special care that its current frontal crash requirements will create maximum fleet safety, if another
round of vehicle weight reductions occur. Further, in adopting new side impact standards,
NHTSA should take care to examine the impact of such standards on the feasibility of moving to
new lightweight designs.
Another compatibility issue may be with roadside hardware such as collapsible light posts and
vehicle barriers. Lightweight vehicles may pose problems for this hardware, because it is designed
to give or collapse under impact forces that may be above the levels achieved by some of the
smaller vehicles.As discussed elsewhere (discussion on advanced materials), current vehicle structural modeling
depends on extensive experience with steel structures. Shifting to aluminum or composites will
provide a substantial challenge to vehicle safety designers, one that may take some time to
overcome. Before the requisite knowledge is obtained, automakers may be forced to “play it safe”
with designs that do not take full advantage of the properties of nonsteel materials.
Many safety advances in the past occurred because biomechanical research identified injury
mechanisms and provided the data that allowed engineers to design restraint systems, padding,
and collapsible vehicle structures (e.g., steering wheels) to appropriate human tolerances.^97 Such
research also has led to the design of improved crash dummies that have greatly improved the
value of crash testing. Further improvement in understanding of injury mechanisms would be
especially valuable, if substantial vehicle weight reduction occurs and adds increased risks to the
vehicle fleet. Unfortunately, biomechanical research is funded at a relatively low level in NHTSA
and is extremely limited elsewhere.^98 This conceivably may limit the industry’s ability to respond
fully to the challenges presented by lightweight advanced vehicles.
Finally, current safety standards focus on designing to protect unbelted occupants as well as
belted ones. Some analysts believe that requirements to protect unbelted occupants compromise
the ability of vehicle designers to provide maximum protection for belted occupants.^99 This issue
may become more intense with extensive reductions in vehicle weights, and the potential for
higher accident intensities that would occur- with such reductions. This is a complex issue that
OTA is not prepared to address at this time, but it is well worth a careful examination.
very high passenger decelerations in the barrier tests. 97
Transportation Research Board, Safety Research for a Changing Highway Environment; Special Report 229 (Washington, DC: National
Research Council, 1990).(^9899) Ibid.
U.S. Congress, Office of TechnologyAssessment Workshop on the Safety of Lightweight Vehicles, Sept. 12, 1994.