Abstract
During a car frontal collision, some part of the occupant's kinetic energy is
transferred to the car through the restraint system such as a seat belt. The high ratio of the
transferred energy in the early stage of collision has the advantage of protecting the occupant.
This phenomenon is called "ridedown effect." It is known from experience that if the
deceleration of the car body is large in the early stages of a collision, the ridedown effect
increases. If the car´s body structure and a restraint system is designed in consideration with
the ridedown effect, good performance can be expected. The relationship between the
ridedown effect and injury criteria should be studied prior to designing a car body.
Knowledge obtained from this study would provide useful information for the initial design
stage. There have been a few studies that analyze the theoretical mechanism of the ridedown
effect in detail.
In this paper, we formulate the ridedown effect, focusing on the work done by restraint
systems using a small-degree-of-freedom model for a car and an occupant. The relationship
between the index of the ridedown effect and the occupant´s deceleration caused by crashing
the car body was analyzed theoretically. As a result, we obtained a new insight, and it was
possible to develop optimum design guidelines for the initial design stage.
Keywords - Safety, Frontal Collision, Ridedown, Occupant Behavior, Car Stiffness