Methodology for assessing high-occupancy toll-lane usage and network performance

A modeling framework for the evaluation of high-occupancy toll (HOT) facilities is discussed. It is based on a traffic simulation-assignment model interfaced with an unordered multinominal logit mode-choice model. The model allows for the prediction of high-occupancy, transit, and single-occupancy vehicle modal shares, based on prevailing traffic conditions and toils. Also presented is an illustrative investigation of the sensitivity to various elements of the modal-choice function using the methodology and of the effect of different HOT facility features on HOT lane usage and associated system performance. These features include HOT lane configurations, pricing levels, carpooling attractiveness, changing departure times, and sensitivity to generalized cost. A representation of the south-central part of I-35W and the supporting roadways in the Fort Worth, Texas, area was used in the study. The results of the simulations were analyzed under each of the operating and behavior characteristics to evaluate the potential success of an HOT facility. Improving the carpooling attractiveness decreases the number of vehicles on the roadway but may not necessarily improve the average travel time for the system as a whole. The larger the departure-time window, the easier it is for travellers to carpool; however, the relatively small number of people choosing the HOV mode may inhibit the average travel time for the system from reflecting the impacts of the reduced vehicle trips. Increasing the sensitivity to time, or generalized cost, raises the HOV mode share when there is an HOT facility available.