Effects of the number of lanes on highway capacity

This paper attempts to investigate the impact of the number of lanes on highway capacity. Methodologically, we provide a better understanding of the relationship between highway capacity and its number of lanes upon the statistical analysis of the survey. The empirical research is validated upon the extensive field survey of traffic flow in Beijing and Shanghai. The findings show that average capacity per lane decreases significantly as the number of lanes increases. Moreover, it indicated that the increase of lane-changing activity and its associated disturbance to traffic stream is the principal factor of the decrease of average capacity per lane on highways. The implication of the marginal decrease requires that the manuals of highway capacity should be revised for the better plan and design of road network. In addition, the factor of the decrease should be incorporated into the decision on adding lanes or constructing a new parallel road when travel demand exceeds road capacity.