Increasing the Capacity of Signalized Intersections

1 Separate turn phases are often used on the approach legs to intersections with heavy left turns. This 2 wastes capacity on the approach because some of its lanes cannot discharge during its green phases. The 3 paper shows that the problem can be eliminated by reorganizing traffic on all the lanes upstream of an 4 intersection using a mid-block pre-signal. If drivers behave deterministically, the capacity that can be 5 achieved is the same as if there were no left turns. However, the reorganization is so drastic that it may be 6 counterintuitive to drivers. This can be remedied by reorganizing traffic on fewer lanes. It is shown that 7 such partial reorganization still increases capacity significantly, even if drivers behave randomly and only 8 one lane is reorganized. The paper shows how to optimize the design of a pre-signal system for a generic 9 intersection. It also identifies both, the potential benefits of the proposed system for a broad class of 10 intersections, and the domain of application where the benefits are most significant. 11 TRB 2011 Annual Meeting Original paper submittal not revised by author. Xuan, Daganzo, Cassidy 3