Modeling Adjustment Factors for Pedestrians and Bicycles on Turning Vehicle Movements at Signalized Intersections

Abstract

At signalized intersections, the capacity of turning vehicle streams can be affected by conflicting pedestrians and bicycles who share the same signal phase. To analyze this effect, measurements at 12 pedestrian and bicycle crossings at signalized intersections in Germany covering more than 4,300 signal cycles were conducted. The reduction in capacity can be accounted for by estimating the blockage time of possible turning vehicle departures. In addition to the pedestrian or bicycle volume, the empirical analyses revealed several other parameters influencing the blockage time such as the duration of the green time and the cycle time of signal control as well as the width of the pedestrian crossing. The influencing parameters were further analyzed by microscopic simulation. Since the current quality-of-service assessment procedures in the U.S. Highway Capacity Manual (HCM) and the German Highway Capacity Manual (HBS) do not consider all of these parameters sufficiently, a new model based on the gap-acceptance theory has been derived. The new model uses the relevant influencing parameters directly as input variables so that a precise calculation of the blockage time is achieved. The new model has been derived in such a way that it can be incorporated into the existing quality-of-service assessment procedures to determine the adjustment factors of the saturation flow rate or the capacity for turning movements. For practical applications, a simplification of the exact model is also presented with a good fit of the data.