Calibrating and Comparing Autonomous Braking Systems in Motorized-to-Non-Motorized-Vehicle Conflict Scenarios

Assuring the safety of all road users, including non-motorized vehicles, is important in the autonomous driving environment. Autonomous emergency braking (AEB) systems have provided an effective way for automated vehicles to avoid collisions with the less easily detectable non-motorized vehicles. Automatic preventive braking (APB) is a new method proposed by Mobileye that promises to reduce crashes without reducing traffic throughput, but APB's effectiveness has not yet been evaluated. This study therefore calibrates and compares the performance of APB with that of one-stage and three-stage AEB braking systems in safety-critical events (SCEs) between motorized and non-motorized vehicles, using SCEs extracted from the Shanghai Naturalistic Driving Study and simulated in MATLAB's Simulink. The evaluation results, which consider both safety and conservativeness, show that 1) one-stage AEB with a deceleration of 5.5\,\text {m/s}^{2} and a time-to-collision threshold of 1.6 seconds can prevent all SCEs from becoming crashes; 2) APB has the best driving stability but its safety performance is inferior to that of the two AEB systems; 3) APB's deceleration process is easily affected by its pre-defined parameters and changing kinetic parameters, which may be one cause of its crashes; 4) AEB's time-triggered braking process is more consistent and reliable than APB's distance-triggered process.