K.S. Machumu, T. Sando, E. Mtoi
Congestion Pricing is increasingly becoming a common strategy for congestion management, often requiring microscopic simulation during planning and operational stages. One of the microscopic simulation issues that has not yet been addressed is the required minimum routing decision distance upstream the ingress point. Decision distance is an optimal upstream distance prior to the ingress at which drivers decide to use express lanes and change lanes to orient on a side of express lanes ingress. To answer this question, this study used a VISSIM model for I-295 proposed express lanes in Jacksonville, Florida, varying the routing decision point at regular intervals from 500 feet to 7000 feet for different levels of service input. Three measures of effectiveness (MOEs); speed, the number of vehicles changing lanes, and following distance, were used for the analysis. These MOEs were measured in the 500 feet zone prior to the ingress. The results indicate that as the level of service (LOS) deteriorates, speed decreases, the number of vehicles changing lanes increases, and the following distance decreases. When the LOS is constant, the increase in the routing distance from the ingress point was associated with the increase in the speed at the 500 feet zone prior to the ingress, less number of lane changes, and the increase in following vehicle gap. However, the MOEs started to be constant after reaching a certain routing decision distance. LOS D was used to determine the minimum routing decision distance to the ingress of the express lanes. The determined minimum distances were 4000 and 3000 feet for six and three lane segments prior to the ingress point, respectively.
Keywords: decision distance; express lanes; VISSIM