智慧型运输系统概论7.pdf

Classic Car-Following Models Dr. Gang-len Chang, Professor Traffic Safety and Operations Lab University of Maryland, College Park 2012.10.02 Outline • Introduction • Model Development • Stability Analysis • Steady-State Flow • Experiments and Observations Introduction • Car following is one of the sub-tasks involved in “driving task”, which needs to be understood. • Car following is defined as one vehicle following another on a single lane of roadway. • Importance of car following: ▫ 1) common practice in driving behavior ▫ 2) contributes significantly to an understanding of traffic flow ▫ 3) forms a bridge between the individual behavior and the macroscopic world Introduction (Cont.) • In car following, one aspect of interest is the average spacing S, that one vehicle would follow another at a given speed V, which could be used to estimate the capacity. • Speed-spacing relation (for steady-state traffic stream): S α=+βV +γV 2 (1) α  : the effective vehicle length, L  : the reaction time, T β γ  : the reciprocal of twice the maximum average deceleration of a following vehicle Introduction (Cont.) • Speed-spacing relation for steady-state traffic stream assumes: ▫ 1) vehicles maintain the same or nearly the same constant speed ▫ 2) vehicles try to maintain the same spacing • with the above assumptions, car following models which can represent the dynamic behavior of a stream of vehicles when acceleration or deceleration is needed. Model Development • Assumptions: ▫ 1) A correlation between vehicles within inter- vehicle range (0-125 m) exists. ▫ 2) The driver