To better understand the characteristics of traffic flow mixed by the cars and trucks on a slope, a cellular automata-based traffic flow model is proposed for single lane traffic. The model takes into account the impact of the slope on the vehicle driving, including the maximum speed, emergency deceleration, general acceleration and deceleration. It also considers the physical differences between cars and trucks, and discriminates the differences among the four car-truck following combinations, car-following-car, car-following-truck, truck-following-car and truck-following-truck. The model parameters are chosen according to the field traffic data, NGSIM data. Based on the proposed model, simulations are conducted to investigate the characteristic of the car-truck heterogeneous traffic flow on a slope. The simulations reveal some new findings. First, the impact of car-truck following combinations on the slope traffic flow is limited in certain thresholds, that is the slope gradient is less than 5% and slope length is less than 60 meters. Second, when slope longitudinal gradient is more than 5%, the traffic capacity of the road is maintained at the same constant value in a certain area of density, and with the increase of slope longitudinal gradient, the unstable region of capacity is gradually widened.

CICTP