Relationships Between Road Horizontal Geometry, Driving Behavior and CO2 Emissions

Exhaust gas emission produced by motor vehicles are mainly caused by the elevation features of the road and by the vehicle type. In truth, there is another contribution, probably lower, that can correlate with the driving behavior. This, in turn, is a function of the road geometry that may thus assume a key role not only in terms of functionality and safety, but also in controlling environmental impacts. In this study, the relationships between the longitudinal acceleration, the CO2 emissions and the geometrical features of the road have been analyzed, to contribute to improving road design quality. The analysis of these potential relationships has been developed through an experimental study in a simulated environment. The results evidenced how the emissions depend on the homogeneity of driving, including variables related to visibility, alignment understanding by the drivers, similarity of adjacent elements. However, some conclusions are interesting because they raise questions regarding the correctness of existing models for operative speed forecasting, available in literature and used to verify the road design homogeneity and consistency. This research may have a positive impact in comparing the road design standards and guidelines of the various countries and, mainly, it may suggest alignment composition procedures based not only on safety and use, but also on environmental impacts.