An Analysis of Express Lanes in Utah

This paper reports on an analysis conducted to identify ways to improve average speeds in the Express Lanes (ELs) in Utah. The research began with an investigation of the current usage of both the ELs and the General Purpose (GP) lanes by user type (e.g., single-occupant vehicle, high-occupancy vehicle (HOV) 2, HOV 3+, “C” decal, Express Pass user, motorcycle, bus, freight vehicle, and emergency vehicle) to better understand the breakdown of vehicles in the lanes and to calculate average vehicle occupancy. Violation data were examined to determine ways to reduce violator rates, while ways to control Express Pass traffic and to evaluate changes to toll rates and to estimate the impacts on speed of specific toll increases along the corridor were explored. The data collected were examined to better understand the speed-flow relationship on the ELs and to estimate the impact of volume changes on speeds in the lanes. This allowed the research team to estimate the impact on EL and GP lane volumes and speeds under a combination of EL education campaigns, increased EL enforcement, and increased EL peak period toll rates. Depending on the scenario analyzed, it was determined that the speeds in the ELs could be expected to increase as a result of the recommendations. The increase was found to be dependent upon the scenario chosen and the response of the traffic to the increases with an average maximum change in EL speed of 7.8 mph for a combination of education, enforcement, and increased tolls.