From traffic conflict simulation to traffic crash simulation: introducing traffic safety indicators based on the explicit simulation of potential driver errors

This paper introduces a general simulation framework that can allow the\nsimulation of crashes and the evaluation of consequences on existing\nmicrosimulation packages. A specific family of simple and reproducible conflict\nindicators is proposed and applied to many case studies. In this approach\ndriver failures are simulated by assuming that a driver stops reacting to an\nexternal stimulus and keeps driving at the current speed for a given time. The\ntrajectory of the distracted driver vehicle is thus evaluated and projected,\nfor the given time steps, for the established distraction time, over the actual\ntrajectories of other vehicles. Every occurring crash is then evaluated in\nterms of energy involved in the crash, or with any other severity index (which\ncan be easily calculated since the accident dynamics can be accurately\nsimulated). The simulation of a driver error allows not only the typology of\ncrashes to be included, normally accounted for with surrogate safety measures,\nbut also many other type of typical crashes that it is impossible to simulate\nwith microsimulation and traditional methodologies being caused by vehicles who\nare driving on non-conflicting trajectories such as drivers speeding at a red\nlight, drivers taking the wrong lane or side of the street or just driving off\nthe road in isolated accidents against external obstacles or traffic barriers.\nThe total crash energy of all crashes is proposed as an indicator of risk and\nadopted in the case studies. Moreover, the concepts introduced in this paper\nallow scientists to define other relevant variables that can be used as\nsurrogate safety indicators that consider driving errors. Preliminary results\non different case studies have shown a great accordance of safety evaluations\nwith statistical data and empirical expectations and also with other\ntraditional safety indicators that are commonly used in microsimulation.\n