This paper attempts to investigate the impact of the number of lanes on freeway traffic characteristics. Methodologically, we provide a better understanding of the relationship between freeway traffic characteristics and its number of lanes upon the empirical analysis. The empirical research is validated upon the extensive field survey of traffic flow in Beijing and Shanghai. More significant improvements are observed on two-lane (in one direction) freeways, then on three-lane freeways as compared to those on four-lane freeways. In congested traffic conditions, at the same densities, both flow rate per lane and average speed decrease with increasing number of lanes on uninterrupted freeway segments. Based on the difference among the speed-density relationships, two different arguments on whether building a wide road or building a number of narrow roads are interpreted. Further it indicates that, the change of lane-changing activity and its associated disturbance to traffic stream causes significant differences in traffic operational characteristics on different-lane freeways. The results of the researches are the background support that tends to revise the highway capacity manuals, optimize planning and design of road network, and improve supervision and control of traffic network.
Abstract