Signalized Intersection Analysis and Design: Implications of Day-to-Day Variability in Peak-Hour Volumes on Delay

Abstract

Traffic signal timing plans are typically developed on the basis of turning movement traffic and pedestrian volume counts aggregated to 15-min intervals and obtained over a 4 or 8 h period on a single day. These data are used to identify the peak hour and to compute the peak-hour turning movement traffic volumes. They may also be used to compute the peak-hour factor. These values are then used as input to the analysis methods defined in the Highway capacity manual or within popular signal timing optimization software to estimate signal performance in terms of expected average vehicle delay. Delay estimation methods explicitly consider several sources of variability (e.g., an assumed distribution of individual vehicle headways in the arrival traffic stream). However, these methods do not consider the day-to-day variability that exists within key delay estimation parameters such as the PHF and peak-hour traffic volume. The lack of consideration of this variability may be because: (1) it is assumed that the ...