Section 1: Introduction
High-occupancy vehicle (HOV) lanes are reserved for vehicles with a driver and one or more passengers. In some cases, other vehicles are also exempted (permitted in the HOV lanes). Examples include motorcycles, transit and charter buses, emergency and law enforcement vehicles, low emission vehicles, hybrid or alternative fuel vehicles, and/or single-occupancy vehicles (SOVs) with a toll. These lanes, which usually run parallel to general-use highway lanes, have been implemented in over 30 US metro areas since they first appeared in the late 1960s and early 1970s. HOV lanes were originally conceived as a means to encourage carpooling and therefore increase person throughput in the transportation system, among other potential benefits like providing reliable transit trip times and increasing roadway capacity while benefiting air quality. The restrictions in these lanes limit traffic demand, which can provide travel time savings along a corridor when compared to adjacent general-use lanes. This travel time advantage is an incentive to drivers to form carpools in order to bypass congestion. Today, there are nearly 350 HOV facilities operating or planned across 20 states.
Unfortunately, HOV lanes do not always provide the expected advantages. Situations frequently arise in which the facility operates with too many (or too few) vehicles during lane operation periods, leading to a number of potential problems. Empty-lane syndrome, the popular term for a condition in which HOV lanes are underutilized, is one common concern. Peak-hour congestion in HOV lanes is another. Striking the proper utilization balance is a challenge for all HOV operators. Add to that the issues that stem from peak directional flows, and the efficient operation of HOV facilities becomes even more complicated. Agencies seeking to avoid or mitigate these lane performances problems will often consider and implement HOV lane policy change as a solution. .
Not all policy changes are motivated by operational difficulties, however. Other motivations for such change include maximizing system throughput, revenue generation (in the case of high occupancy toll (HOT) lanes), and legislative mandate. Opportunities for getting more vehicles through a particular corridor almost always exist, and changes to HOV policies can help to realize throughput gains. Implementation of tolling on HOV lanes can also provide revenue for lane maintenance or expansion, transit improvements, or other purposes in the region. Legislation can also drive policy change. HOV operators are currently required to consider policy changes if average speeds in the HOV lanes drop below 45 mph for 90 percent of the time over a consecutive 180-day period during the weekday peak periods (23 USC. 166 (d)(2)(B). And some operators have had to adjust their policies based on laws that allow hybrid vehicles to use the lanes without charges. Finally, Federal initiatives, such as the Value Pricing Pilot Program and the Urban Partnership Agreement, encourage pricing experimentation and have in some cases included policy changes to existing HOV lanes to serve as tests leading to wider implementation.
This study examined the performance of HOV lanes with regard to the goals and objectives under which existing HOV lane facilities were deployed. Also addressed are factors that can best contribute to the success of HOV lanes, through targeted and focused outreach to HOV operators. Identification and improved understanding of these factors can contribute to effective policy change decisions that improve performance of existing and future HOV facilities.
The study consisted of the following four tasks:
The remainder of this report is organized according to the following sections:
United States Department of Transportation - Federal Highway Administration