Probabilistic risk assessment for pedestrian-vehicle collision considering uncertainties of pedestrian mobility

<b>Objectives</b>: The uncertainties of pedestrian mobility are important factors affecting the accuracy and robustness of an active pedestrian protection system. This study is to provide the means for probabilistic risk evaluation of pedestrian-vehicle collision by counting the uncertainties in pedestrian motion. <b>Method</b>: The pedestrian is modeled by the first-order Markov model to characterize the stochastic properties in mobility according to the field experiments of pedestrians crossing uncontrolled road. Based on the assumption of Gaussian distribution, Unscented Transformation (UT) is employed to predict the collision risk probability with the symmetric σ-set constructed on the basis of discrete trajectory simulation. Simulation experiments were carried out with 10000 Monte Carlo (MC) simulations as the reference. <b>Results</b>: The probability density distributions of Time-To-collision, minimal distance and collision probability estimated by UT coincide with the reference ones under various vehicle-pedestrian conflict scenarios, and the maximal deviation of collision probability from the reference is 5.33%. The UT method is about 600 times faster than MC method (10000 runs), which means the proposed method is with the potential for online application. <b>Conclusions</b>: This paper presents an effective and efficient algorithm to estimate the collision probability by using UT method to solve the nonlinear transformation of uncertainties in pedestrian motion. Simulation results show that UT-based method achieves accurate collision probability estimation and higher computation efficiency than MC, and provides more valuable information concerning collision avoidance than the deterministic methods in the design of a pedestrian collision avoidance system.