A Simulation Framework for Assessing the Safety Effects of Soft and Hard Shoulders as Examples of Forgiving Roadside Treatments

This paper proposes a novel approach for analyzing the necessity and effectiveness of forgiving roadside design that aims to mitigate the consequences of run-off-road accidents (RORA). A framework is presented, which comprises the development of road, vehicle and driver models in order to simulate specific RORA scenarios. These scenarios are based on data taken from the Austrian road accident database that contains more than 650,000 personal injury accidents since 1994. Three-dimensional road models (including the roadside) created from laser measurements allow integrating accurate replications of existing accident high-risk sites in simulation. For each “virtual” high-risk site, the roadside is then modified with appropriate safety treatments, before run-off-road accidents are simulated. Indicators for the effectiveness of roadside treatments are the head injury criterion (HIC) and the abbreviated injury scale (AIS) Simulation results show that the risk of fatal injuries strongly declines with forgiving roadside design. For a specific accident high-risk site, safety treatments with hard and soft shoulders are investigated in the simulation. The results show that the implementation of hard shoulders mitigates the risk of severe injuries.