Drivers’ speed behaviour in real and simulated urban roads – A validation study

Traffic accidents and injuries constitute a growing problem for Europe’s urban transportation system. Driving simulators can be active support tools in the design process of urban driving environments, provided that they are appropriately validated. The aim of this study was to establish the behavioural validity, in relative and absolute terms, of the motion-base driving simulator of the Road Safety and Accident Reconstruction Laboratory (LaSIS) of the University of Florence in order to use it to evaluate the effectiveness of the urban road safety treatment design process. The research was conducted by comparing the driving speed collected in field with those recorded in the 3D virtual reality experiments through conventional and integrative statistical methods. Speeds were recorded at twenty-one measurement sites located in homogeneous road sections characterized by a less or more demanding driving environment; thirty-four participants drove the virtual scenario which reproduced the real situation. The results of the comparative and conventional statistical analysis established the relative validity and also revealed that absolute validity was obtained in the measurement sites in which physical constraints are imposed by engineering treatments. The integrative regression analysis confirms these outcomes and showed that the simulation system is a reliable predictor of the real speed data also in absolute terms. It was also found that the driving experience levels significantly affect the speed adopted by the motorists in the virtual environment. These findings support the use of the driving simulator as a powerful approach to predict of the safety effectiveness of design solutions in urban areas, thus allowing important cost savings.