Influence of Road Geometric Design Consistency on Familiar and Unfamiliar Drivers’ Performances: Crash-Based Analysis

Drivers’ road familiarity is a safety-related factor. Familiar drivers may be prone to inattention and more dangerous behavior, whereas unfamiliar drivers may be affected by demanding and unexpected road environments. Previous research adequately described the role of familiarity in driving behavior and road safety performances. However, the relationships between drivers’ unfamiliarity and safety issues of road design elements are still largely unexplored and there is a lack of dedicated experimental studies. In this work, a database including run-off-road single-vehicle accidents at Norwegian rural two-lane road curves was investigated. Information about familiarity was derived from the distance from the residence of drivers involved in crashes. Road geometric variables were collected on the segment before the accident site, to provide indicators of design consistency of the previous road section. Thereafter, logistic regression was used to find relationships between predictor variables related to the geometric road design consistency and familiarity (the dependent variable). As a result of the analysis, familiarity was confirmed as a factor associated to possible dangerous behavior such as speeding in demanding road environments. However, crashes involving unfamiliar drivers are associated to unexpected curve parameters (radius and length) and the combination of horizontal and vertical curvature. Thus, as well as familiarity, drivers’ unfamiliarity may be considered as an accident factor. Moreover, some possibly useful consequences for road design are suggested for practitioners. They specifically concern provisions about radii of subsequent curves and coordination between radii of horizontal and vertical curves.