New consistency model based on inertial operating speed profiles for road safety evaluation

Abstract

[EN] Road crashes are mainly caused by three concurrent factors: infrastructure, vehicle and human factor. The interaction between infrastructure and human factor leads to the concept of geometric design consistency, which can be defined as how driver¿s expectations and road behavior fit. This paper presents a new global consistency model based on the difference between the inertial operating speed profile (Vi) and the operating speed profile (V85). The first one is calculated as the weighted average speed of the previous road section and represents drivers¿ expectations, whereas the second one represents road behavior. A set of 71 homogeneous two-lane rural road segments located in Italy were used in the calibration of the model. As a result, a Safety Performance Function based on this new consistency model was proposed in order to estimate the number of crashes in an entire road segment. Finally, the new model was compared with previous global consistency models, concluding that the new consistency parameter better explains the phenomenon than the previous ones. Therefore, the new consistency model is a useful tool for the engineers which allows estimating the number of crashes and incorporate road safety to the geometric design of both new two-lane rural roads and improvements of existing highways.