Pedestrian Crossing Time in Determining Widths of Signalized Traffic Arterials

Widening of traffic arterials at signalized intersections is often done with the intention of increasing vehicular capacity of the intersection. An analysis of the impact of increased pedestrian crossing time resulting from the widening (particularly on undivided arterials) on capacity is presented. It is shown that when signal cycle length is fixed, pedestrian crossing time imposes an upper limit on vehicular capacity of the arterial, so that its widening yields diminishing increases in capacity. There is a width beyond which capacity decreases. Relatively simple formulas and diagrams for deriving maximum capacity taking the pedestrian factor into account are presented. Short of adjustments at other points of the street network, grade separations, etc., provision of a protected pedestrian island in the middle of the arterial is suggested as the only acceptable solution to this problem.