This synthesis will be of interest to transportation planners, highway engineers, environmental personnel, highway design engineers, transit planners, highway administrators, and others concerned with the planning, design, and operational features of preferential high- occupancy vehicle (HOV) lanes on highways. Information is provided on the current and proposed state of the practice in North America. This synthesis describes the state of the art with respect to preferential treatment for HOVs on highways. This report of the Transportation Research Board provides information on long-distance facilities, such as barrier-separated, concurrent-flow (separated and nonseparated), and contraflow facilities, as well as on short-distance facilities, such as queue by-pass lanes. Planning, design, and operational features of each treatment are described. The issues and operating results are described, and specific case studies are included.