Best Practices: Separation Devices between Toll Lanes and Free Lanes

Transportation agencies around the nation find themselves pushing the envelope of innovation to keep up with congestion caused by exploding demand for limited roadway space. Managed lanes provide a mechanism for harnessing the potential of the current infrastructure. Special-purpose lanes, including high-occupancy vehicle (HOV) and high-occupancy toll (HOT) lanes, allow engineers to manipulate roadway parameters to achieve varying levels of service. Managed lanes are controlled access facilities, and must somehow be separated from general-purpose lanes. One principle question that must be asked is what type of delineation technique should be used? What are the properties of different delineators that make some more favorable than others? How do roadway characteristics, such as available width and traffic volume, factor into the choice of delineation? Much has been written on the safety and cost aspects of different delineation techniques used for HOV lanes; are these analyses applicable to other managed lanes as well? What about the other characteristics of the techniques: what are they, and how important are they to the choice of delineation? This report addresses some of these questions and sheds some light on their ultimate answers. Three basic categories of delineation exist: concrete barriers, pylon posts, and painted buffers. This research project assembled an expert panel to gather a collective knowledge of factors involved in the choice of delineation most appropriate to given scenarios. The summary of this panel’s discussions, included in this report, will serve as a useful guideline for engineers looking to choose the best type of delineation for future, successful managed lane projects.