Analysis of Operational Interactions between Freeway Managed Lanes and Parallel,General Purpose Lanes

Roadway agencies face growing challenges to expand freeway capacity. Under the constraints of rising construction costs, right-of-way limitations, and environmental regulations, transportation agencies are seeking solutions for efficiently managing the demand on existing freeway facilities and for providing options for travelers. The concept of managed lanes (MLs) is an increasingly popular countermeasure that aims to make the most efficient use of freeway facilities by restricting access to one or more lanes to certain vehicle classes on a facility that is parallel to existing general purpose (GP) lanes. With different strategies for separating ML and GP lanes, this study examines the interaction between GP lanes and ML operations. It scrutinizes this interaction as a function of different separation types, the number of MLs, and operational ML strategies, including high-occupancy toll (HOT) and high-occupancy vehicle (HOV) lanes. Four freeway sites were selected to explore the effect of this interaction. The research shows that, for HOT facilities, separation type has the most significant impact on explaining the intensity of the frictional effect, as paint-separated ML facilities are readily affected by congestion in adjacent GP lanes. For HOV facilities, the frictional effect was observed by adopting a stochastic approach to capacity estimation to estimate the capacity distribution function for both GP and HOV lanes. It was determined that GP lanes had a stochastic dominance over HOV lanes under any breakdown probability. The results make the case that ML operations should not be evaluated independently of adjacent GP lanes, and these results have implications for both proposed analytical approaches and simulation-based analyses.