Frontal Impact When a vehicle runs into a fixed object or another vehicle in a frontal
collision, there is a sequence of events that takes place within a fraction of a second. At
very low speeds, the bumper and its mounting will absorb the energy of impact. The
NHTSA Bumper Standard establishes that a passenger vehicle bumper should absorb the
energy from a 2.5mi/hr impact of the vehicle. For a time, the standard was a 5mi/hr impact,
which some manufacturers still meet. At higher speeds, the structure of the vehicle will
absorb the energy of impact by crushing. Today’s vehicles are designed to absorb a great
deal of energy; older vehicles were not. Because of the absorption of energy by the struc-
ture, the rate of deceleration falls quickly with distance from the point of impact. Figure
14-1 illustrates this concept by plotting G load (the ratio of impact deceleration to the pull
of gravity). At some distance from the point of impact, there is little deformation of the
vehicle structure, and from that point on, the deceleration rate is fairly constant over the
rest of the vehicle length.
Frontal Impact When a vehicle runs into a fixed object or another vehicle in a frontal collision, there is a sequence of events that takes place within a fraction of a second. At very low speeds, the bumper and its mounting will absorb the energy of impact. The NHTSA Bumper Standard establishes that a passenger vehicle bumper should absorb the energy from a 2.5mi/hr impact of the vehicle. For a time, the standard was a 5mi/hr impact, which some manufacturers still meet. At higher speeds, the structure of the vehicle will absorb the energy of impact by crushing. Today’s vehicles are designed to absorb a great deal of energy; older vehicles were not. Because of the absorption of energy by the struc-ture, the rate of deceleration falls quickly with distance from the point of impact. Figure 14-1 illustrates this concept by plotting G load (the ratio of impact deceleration to the pull of gravity). At some distance from the point of impact, there is little deformation of the vehicle structure, and from that point on, the deceleration rate is fairly constant over the rest of the vehicle length.
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