Development of a new integrated surrogate safety measure for applying in intelligent vehicle systems

This paper aims to develop a new Surrogate Safety Measure (SSM) for applying in In-vehicle collision avoidance warning systems. To send safety alarms, the amount of collision risk is required, which of course can be measured with only one measure. To accurately determine the risk of an accident at any given time, 7 valid safety measures including Time to collision (TTC), Modified TTC (MTTC), General formulation for TTC (GTTC), Deceleration-based surrogate safety measure (DSSM), Difference of Space distance and Stopping distance (DSS), Deceleration rate to avoid collision (DRAC), and Proportion of Stopping Distance (PSD) were used together and with different thresholds to provide a more accurate estimate of the risk for each moment. A certain range of thresholds was assigned to each of the mentioned measures. As a result, Adequate number of thresholds (in this paper 800 thresholds) were created for the 7 measures. One of the advantages of this system is that it not only considers the present time to provide an alarm, but also the recent past of the vehicle (the last half-second). This means that the proposed integrated measure can determine the risky situations by considering the past and present of the vehicle. Finally, given the estimated collision risk and also based on the ascending or descending trend of the risk according to the vehicle's past situation, five alarm types were designed. The greater the risk of a collision in a moment, the stronger and more efficient the alarm type.