Modeling speed differential parameters in day and night environments using driving simulator

The study presented in this paper is aimed at analyzing the drivers’ speed profiles for the evaluation of speed differentials parameters (85MSR, ΔV85 and Δ85V) during day and night driving. Speed differential parameters are commonly used for design consistency evaluation, according to an advanced approach of road engineering, based on the study of the roadway's conformance to driver expectancy that can improve road safety performance. The research was carried out using a driving simulator where a section of 10 km of an existing two-lane rural road composed by 39 tangent-curve configurations was implemented. The speed profiles of 40 drivers were recorded both in simulated daylight and nightlight driving conditions. The study proposes new relationships between speed differential parameters for different visibility condition and geometries of tangent-curve configurations and increases the actual knowledge of driver's speed choices and driving behaviour under nighttime conditions. Specifically, results demonstrate different relations between speed differential parameters among four different classes of tangent-curve geometries and under day and night driving conditions. Relations are also compared with the main literature models that correlated speed differential parameters.