Safety Analysis for Automated Transportation Systems

This paper outlines an approach to analyzing the safety characteristics of vehicular ground transportation systems operated under computer surveillance and control. A quantitative index of safety is formulated, and a procedure is developed for analyzing the dependence of system safety on the significant design parameters and performance attributes. Lower bounds on the permissible minimum headway are established on the assumption of instantaneous and perfect control, so that the effects of various sensing, communication, control and actuation subsystems can be assessed independently. Time delays in emergency control—resulting from discrete sensor spacing, finite sampling time, and loss of telemetered data—are analyzed and expressions for the attendant increase in the minimum headway are developed. The general approach and the specific techniques are illustrated with numerical examples.