Analytical Method for Estimating Delays to Vehicles Traversing Single-Lane Roundabouts as a Function of Vehicle and Pedestrian Volumes

Modern roundabouts that have unsignalized pedestrian crossings typically provide right-of-way to pedestrians, and therefore vehicles entering or exiting the roundabout must yield to pedestrians. The requirement that vehicles seek gaps in the pedestrian stream results in four distinct sources of delay to vehicles traversing the roundabout. Existing analytical methods for estimating delays to vehicles entering roundabouts typically consider only one of these four sources and ignore the other three. This paper presents an analytical model for estimating delays to vehicles traversing a single-lane roundabout. The model is based on gap acceptance and queuing models and explicitly estimates delays for each of the four sources for each origin–destination movement in the roundabout. The proposed model is evaluated for a typical single-lane roundabout by comparing the model estimates with estimates obtained from the VISSIM simulation model and the Highway Capacity Manual (HCM) method for a range of traffic and pedestrian volumes. The results of this evaluation demonstrate that the proposed model is superior to the HCM method and provides delay estimates that are comparable with those obtained from microsimulation modeling. Further research is recommended to validate the model results by using field data.