How to define the accident risk level of car drivers by combining objective and subjective measures of driving style

- Understanding accident risk perception is necessary in order to increase road safety levels.
- Accident risk perception is often subjectively evaluated, being risk perception as highly individual.
- Both subjective and objective measures of driving style are necessary for identifying accident risk.
- The concurrent use of speed and longitudinal and lateral acceleration more reliably defines driving style.

Perceived risk can be defined as the expectation of being involved in a traffic accident. Traffic risk perception is often subjectively evaluated being risk perception as highly individual, and depending on experiences with accidents. For this reason, a subjective measure of risk level can be useful. On the other hand, accident risk level can be measured also through objective measures, consisting in kinematic parameters defining the driving style. At this aim, it is very important to analyse instantaneous and geo-referenced travelling kinematic parameters of the vehicle recorded by real tests on the road.The aim of this paper is to identify the accident risk level of each driver based on a methodology combining both subjective and objective parameters. Specifically, by using the proposed methodology the risk can be measured immediately by using only the kinematic parameters adopted when driving; we defined three levels of risk of being involved in a road accident (low, medium, and high risk). We retain that our research can give a contribution in terms of improvement of road safety, because the distorted perception of risk level is one of the main causes of road accidents. Very often, drivers are not aware of the risk taking; therefore, it is necessary to raise the awareness of drivers to have safer driving. The proposed method can be useful for informing the driver on the level of risk he/she assumes, so that he/she can take the necessary precautions next time that will cover that stretch of road.