Impact attenuation devices are employed to minimise the adverse effects of a run-off-the-road accident. In particular, crash cushions should trap or redirect the errant vehicle without subjecting its occupants to unacceptably high dynamic forces. This paper describes the development of the connecticut attenuator design system (CADS), which implements a design strategy for a generalised version of the connecticut impact attenuation system (CIAS) when supplied with basic information concerning the dimensions of the site and the design speed of the roadway. The program incorporates the crash testing guidelines and performance requirements of NCHRP report 230, along with an accurate mathematical model of the vehicular and occupant impact responses. Turbo pascal is employed as the implementation language using an object-oriented programming approach. The knowledge used to design the impact attenuator as well as the knowledge representation are described. The validity of the techniques is demonstrated by comparing the mathematical simulation to actual full-scale crash test results. An example problem involving 60-mph impacts with 1,800- and 4,500-lb vehicles is presented in which the crash cushion configuration and individual energy dissipating components are designed in such a way that the occupant risk parameters are minimised.
Abstract