Abstract
The time headway and space headway of mixed traffic flow composed of small cars and heavy vehicles are studied in this paper based on the theory of car-following and probabilistic method, so as to respectively obtain the average time headway and average space headway. Therefore, the theoretical models of the average time headway and average space headway were obtained from the classic ones. From the theoretical models, we know that different proportions of different vehicle models have a certain impact on the theoretical capacity of the trunk road section. As the proportion of heavy vehicles increases, the theoretical capacity of the trunk road section will decrease. The impact and modification of three factors like number of lanes, lane width and plane intersections on the theoretical capacity are further discussed in this paper, so as to obtain the capacity model of the actual trunk road section. Finally, the correctness and consistency of the capacity model are proved through the calculation of the living example, and the changing trend of the traffic capacity of mixed traffic flow under different vehicle proportions is analyzed, so as to conclude that the proportion of vehicles has a certain influence on the capacity of the road segment.