Road safety: methods to predict the safety level of a freeway

Aim of this paper is to find the relationship between road design and accident risk, taking into account the driver’s behaviour. Even if it respects all the standards and regulations in force, a road can be very dangerous when drivers cannot understand its evolution, therefore facing a curve with unsuitable speed or following trajectories different from the designed one. This happens when the driver has not all the information he needs to decide the manoeuvre he is going to do, or when he has not the skills to manage that information. This lack of knowledge and experience leads to a status of insecurity and uneasiness which increases the probability of car accidents. In our study, three indexes are introduced, able to identify the level of risk of a freeway. They do not consider only road geometry, but all the relationships existing between man, vehicle and road environment. To verify their accuracy, some trials have been conducted with an instrumented vehicle along a selected path, showing that each index can detect a dangerous road segment, giving information to road designers to improve the safety level of that freeway.