The Influence of General Purpose Lane Traffic on Managed Lane Speeds: An Operational Study in Houston, Texas

Freeway networks are a critical component of the transportation systems at large metropolitan areas. The use of managed lanes (MLs) is a very important tool in accommodating directional demand, often heavily asymmetrical at peak hours. Current literature establishes that operational performance of MLs may impact, and be impacted by, operations of adjacent general purpose lanes (GPs), despite some degree of physical separation. Such operational co-dependence may especially exist between the GP lane adjacent to the separation buffer and the ML lane. This paper examines how the operations of these lanes relate to each other. Operational data were collected from 2 freeway sites in Houston TX (U.S.A.) for analysis. Both sites feature a buffer separating a single ML from the GP lanes at each site. One of those sites features vertical pylons in its buffer while the other site does not. This dataset spans several months of year 2014, from January to December. Results highlight the influence of the left-most GP lane on the ML operational speed, as well as the apparent degree of mitigation to that influence that the presence of pylons provides.