Modeling and Analysis of the Car-truck Heterogeneous Traffic Flow Based on Intelligent Driver Model

1 The traffic flow heterogeneity caused by the different car-following dynamics among the different types 2 of vehicles has drawn increasing attention recently. This paper explores the characteristics of the four 3 types of car-truck car-following combinations, car-following-car (CC), car-following-truck (CT), truck4 following-car (TC) and truck-following-truck (TT), and their impacts on traffic flow stability. A 5 heterogeneous traffic flow model based on Intelligent Driver Model (IDM) is proposed and calibrated 6 using the Next Generation Simulation (NGSIM) vehicle trajectory data. Based on the calibrated model, 7 the characteristics of the car-truck heterogeneous traffic flow are evaluated using the linear stability 8 analysis, fundamental diagrams, and shock wave characteristics. The linear stability analysis identifies 9 two critical factors that can influence the stability of the car-truck heterogeneous traffic flow: the 10 stability functions and the proportions of the four types of car-truck combination. Cars and trucks can 11 both stabilize and destabilize the traffic flow depending on the combination type and the equilibrium 12 velocity. Fundamental diagrams of car-truck heterogeneous flow are found to be determined by the 13 distance headways and proportions of the four types of combination. Moreover, the fundamental 14 diagrams of different car-truck combinations converge to several clusters with the same proportion 15 difference between the CC and TT combinations. The slowing-down effect of trucks on shock wave 16 speed in the car-truck heterogeneous traffic flow is also observed in the simulation. 17 18