Behavior-based analysis of the relationship between expressway capacity and number of lanes

The impact of the number of lanes on expressway capacity is investigated. Methodologically, a better understanding of the relationship between expressway capacity and the number of lanes is provided through empirical study and behavioral analysis. The empirical study is validated by using the extensive field survey of the traffic flows in Beijing and Shanghai. It is found out that the average capacity per lane decreases marginally with increasing number of lanes on uninterrupted expressway segments, which implies that the manuals of expressway capacity should be revised for better planning and design of road networks. An analysis of driving behavior indicates that the increase of lane-changing activity and its disturbance to traffic is the principal factor for the decrease of average lane capacity on expressways, which should be incorporated into the decision on whether adding lanes or constructing a new parallel road when travel demand exceeds road capacity.