Case Study Application of TNCC: A Simulation Tool to Identify Plaza Bottlenecks on a Toll Network of Highways

Toll Network Capacity Calculator, TNCC, determines the optimum number of vehicles and/or passenger car equivalents that can pass through all available lanes at a toll collection facility in one hour. The capacity depends on the number of lanes available at the plaza and the processing rates for each of the customer-groups served in the lanes. The capacity also depends on the distribution of the arrival volumes among the customer-groups. In other words, the percentage of arrival volumes belonging to each of the customer-groups is an important factor in the determination of the maximum throughput. TNCC was applied to 58 toll plazas on the toll network in Orange County, Florida, maintained by the Orlando Orange County Expressway Authority, OOCEA. Four categories of vehicles or customer-groups were identified in this study. Videotapes of the throughputs at the plazas provided the processing rates for the customer-groups. The distribution of the arrival volumes among the customer-groups was extracted from transaction data. Once capacities were calculated throughout the toll network, potential bottlenecks were identified, generally centered around urban highway segments. At plaza bottlenecks, lane configurations were altered by TNCC and new capacities were determined. Through the software, it was possible to find the optimal lane configuration for maximum throughput at each of the 58 toll plazas.