In a previous experimental study, a comparison was made between
a 1978 Pontiac LeMans car front with a standard bumper and the same
front with a more compliant bumper developed by the National
Highway Traffic Safety Administration (NHTSA). The tests were made
with the two car front and bumper systems mounted at the normal
bumper level 45 cm and with a lower front configuration with the
bumper level 32.5 cm above the ground. The experimental biological
model system developed at Chalmers University of Technology for
detailed kinetic analysis of car front to leg impact sequences was
used for this comparison. The tests were carried out at 30 to 32
km/h impact speed. A significant difference was found only between
the standard bumper in the higher position and the compliant bumper
in the lower position.
A still more compliant bumper than that used in the previous
test series was produced by NHTSA and tested with the front and
bumper system in the normal position 45 cm above the ground. Ten
impacts to the biological model were made at 32 km/h with loaded
and unloaded specimens, and five impacts were made at 20 km/h with
unloaded specimens.
Damage to the knee was seen, including fractures of the knee
condyles, in two tests with the loaded specimens. Knee ligament
tears were observed in all the tests, indicating the importance of
the inertia of the lower leg and foot when the impacts occur at
knee level. The modified, more compliant bumper in this test series
caused equally serious damage to the knee as did the slightly
stiffer bumper in the previous series.