The role of geometric road design parameters in driving speed negotiation and safety perception: objective and subjective measures in simulation study

The critical point in rural road safety and road design is evaluation of perceptual properties of road curves. This study presents research project which deals with geometrical aspects of spatial road design that enhance road safety. Research focuses on road curves design rules elaboration which support safety, according to Self Explaining Roads (SER) concept. The main aim was to test the driver’s behavior and speed effects of driving through rural roads with different geometric parameters (width and number of driving lanes, curvatures, transition curves, etc.) and roadside visible characteristics. The laboratory experiment, pilot studies and the main experimental works were conducted at driving simulation laboratory of Italian Interuniversity Research Centre of Road Safety, CRISS. Analysis presented in the paper are focusing on relations between experimental variables and driver’s behavior related to driving speed and other advanced behavioral indicators connected to driving trajectory, speed choice, risk perception and curve geometry. The additional analysis of the subjective safety and perceptual qualities of the simulated road is shown, to disclose the relations between subjective and objective measures of road safety. The questionnaire results coupled with simulation experiment showed relations between driver’s behavior to gender and driving experience of subjects. The study results demonstrate the effectiveness of clothoids as transition curves in road paths in terms of road safety and the effects of road visibility on driver’s behavior under different geometrical conditions and road scenario. The general results show that the advanced techniques of visualization and simulation of road space can better than qualitative measures disclose the relationships between design road parameters and behavioral aspects important to create safer road infrastructure.