2.0 High-Occupancy Vehicle Facilities

Restriction of certain roads or lanes to, or construction of such roads or lanes for use by, passenger buses or high-occupancy vehicles.
Section 108 (ii), CAAA

Introduction

According to EPA, high-occupancy vehicle (HOV) lanes are one of the most frequently implemented mobile source emission reduction measures. HOV lanes are designated exclusively for use by vehicles with multiple occupants such as carpools, vanpools, and transit vehicles. Implementing HOV facilities can involve adding entirely new capacity or reallocating existing capacity. Along with a range of physical options, HOV facilities have operative options such as full-time HOV-only use, peak time use, and reversing the travel direction of facilities during peak times. HOV lanes can increase transit use and car occupancy for work-related trips in congested urban travel corridors.

Main Components

The most effective HOV lane improvements generally involve regional networks of linked lanes, with a system of supporting facilities and services. Historically, the most successful HOV applications have been along “radial” corridors into major central cities where HOV users can save at least 10 minutes of travel time compared to using mixed-traffic lanes. EPA studies show that HOV lanes are generally more effective if implemented along with transit improvements, park-and-ride facilities, employer-based transportation programs, and commuter parking subsidies.

Because of substantial physical and financial requirements, state departments of transportation (DOTs) usually are the agencies to implement HOV lanes. Historically, the EPA has found the typical time frame for implementing HOV lanes is three to eight years for planning, design, and construction. Private or nonprofit authorities may construct and operate HOV facilities along toll roads (high-occupancy toll [HOT] lanes). Operators can use discriminatory pricing strategies such as granting toll discounts to HOVs to promote utilization.

Potential land acquisition often determines feasibility and the time required to implement the project. Also, HOV project planning and design is a political process involving various parties, including political leaders, business groups, and citizen groups. Discussions and negotiation among them, while very important, may add time to the project.

HOV projects can be very expensive, depending on such factors as right-of-way acquisition or cost of land, bridge and overpass modifications, and interchange and ramp modifications to provide access. Total costs of some HOV projects have exceeded several hundred million dollars.

HOV impacts on air quality are fairly complex, but Los Angeles, San Francisco, Washington, D.C., and Portland have documented emissions impacts from their HOV projects. Assessments of the effectiveness of HOV lane facilities in reducing system-wide emissions have generally found reductions amounting to less than 1 percent.

HOV lanes reduce air pollution emissions by reducing running and trip-end emissions. Reductions in running emissions are derived by increasing average speeds from low speeds in congested traffic to 50 mph in HOV lanes, and increasing the use of buses, vanpools, and carpools results in less VMT. If riders do not take additional trips, HOV lanes will also reduce trip-end emissions. However, if users of HOV lanes meet their pool or bus through a park-and-ride arrangement, these trip-end emissions may offset the reduced air emissions benefits. When calculating the effectiveness of HOV lanes in reducing emissions, trip-end emissions resulting from using linkages must be considered.

Other Considerations

Two important factors in implementing a successful HOV program have been identified. Enforcement is critical. EPA studies show that early and substantial enforcement of HOV rules on a new facility is the best determinant of long-term public compliance. Also, education and marketing programs that promote the benefits and use of the HOV facilities, both during and after construction, increase the potential for users of the facility.