An accident-severity analysis for a uniform-spacing headway policy

Future automatic highway systems should operate at high capacities (≥3600 vehicles/lane/h) over a range of highway speeds (13-26.8 m/s). Under such conditions it would be impossible to eliminate accidents. Here, a methodology to ascertain the severity of one especially critical accident, multivehicle collisions resulting from the emergency braking of a platoon of automatically controlled, closely spaced vehicles, is presented. This includes the specification of a collision model, which was based on reported crash-testing results, the selection of an accident-severity measure, a consideration of a corresponding cost function, and a sensitivity analysis to determine those parameters which most heavily impinge on accident severity and/or cost. The utility of the methodology was demonstrated by applying it to three platoon-accident scenarios which would be especially relevant to automated highway operations, and a quantitiative measure of the effects of key parameters on accident severity is specified. Such results would be of considerable use to a system designer.