State by state data tables:

• Comparable Regions for 2001 (pdf 278 kb)

There are over 2,000 lane miles of high occupancy vehicle (HOV) facilities now in operation in the United States. Nearly all of these were built within the last 30 years. This analysis focuses on freeway HOV systems in large metropolitan areas comparable to the Puget Sound region.

The Puget Sound freeway HOV system consists of approximately 200 miles of HOV lanes, freeway-to-freeway HOV connections and access ramps. Few regions of the country have such extensive systems. The regions that have HOV systems that are roughly comparable to the Puget Sound system include:

• Los Angeles
• Atlanta
• San Francisco Bay area
• Phoenix
• Dallas

As diverse as these areas appear, they have common urban mobility problems. Each of these areas has a metropolitan area population in excess of 2.5 million, all have experienced rapid population growth over the last twenty years, and each has significant traffic congestion problems.

What trends did this operating policy review reveal?

• A range of HOV operating policies have been developed by regions around the country in response to local traffic conditions, transit system needs, and political considerations.
• Large metropolitan areas with extensive interconnected HOV systems tend to have uniform HOV operating policies.
• There have been few system-wide changes in HOV operating policies among the larger HOV systems.
• Both peak hour and all-day HOV operating polices are used. There appears to be a preference for 24-hour 7 day per week operating policy in the larger HOV systems.

Uniform operating policies
The metropolitan areas with extensive HOV lane systems tend to have a uniform operating policy for all, or nearly all, HOV lanes within the region. Los Angeles, Atlanta, Dallas and the Puget Sound area all have 24 hour/seven day per week operating policies with a few limited exceptions. The San Francisco Bay area and Phoenix have adopted peak hour HOV lane operating policies with a fairly high degree of uniformity among connecting facilities. Ease of enforcement, driver expectancy, and system continuity were all cited as advantages of having a uniform regional operating policy, regardless of whether the policy was for peak hours or all day.

All day or peak hour HOV lanes
The metropolitan areas with extensive interconnected HOV systems are more likely to have 24 hour per day HOV eligibility requirements. There are, however, examples of metropolitan areas that have adopted peak period HOV lane operating policies. Both the San Francisco Bay area and the Phoenix area have peak period HOV operating policies for their HOV systems.

Changes in HOV operating policy
HOV lane operating policies have tended to remain unchanged in the regions with comparable HOV systems. The most frequent change has been adjustment in the hours of operation for peak period facilities. A number of other facilities have reduced the occupancy requirement from 3+ to 2+, or from bus-only to HOV. But there have been no system wide changes from peak period to all day, or from all day to peak period. It should be noted that, like the Puget Sound region, HOV systems in other areas are still growing. As travel demand grows and HOV facilities are extended, it is reasonable to expect operating policy issues to be revisited.

Even though there have been few changes in operating policy, hours of operation and occupancy requirements have been discussed frequently. California is presently conducting a demonstration of peak period HOV policy on SR 14, a 15-mile long freeway in L.A. County. This is one of the few freeway HOV facilities in the Los Angeles area that is not restricted to HOV use 24 hours per day seven days per week. SR 14 does not connect to HOV lanes on other freeways, though plans call for connecting HOV facilities to be built in the future. Results of the demonstration project should be available later this year.

The changes in operating policy that have been made have nearly always been toward more permissive policies. There are very few examples of HOV facilities where more restrictive eligibility requirements have been adopted after a facility has been opened, though there have been instances where HOV operating hours have been extended to encompass expanding peak travel periods. Authorities responsible for HOV policy have observed that the public far more readily accepts adjusting hours of operation, even if it involves extending HOV hours, than increasing occupancy requirements.

There have been several examples of HOV lanes that have either been converted to general-purpose (New Jersey), or where conversion to general-purpose use was considered but rejected (Minnesota). These were unique cases that have little in common with the HOV system in the Puget Sound region. In both instances the HOV lanes were isolated facilities that operated far below capacity even in peak travel hours. In the New Jersey case, transit service was minimal and HOV usage trends did not suggest the facility would be efficiently utilized in the foreseeable future.

Weekend use of HOV lanes
Systems that operate peak hour HOV lanes allow weekend use by general-purpose traffic. Systems with all day HOV lane-operating policies extend that requirement to weekend operation. There are no exceptions to these practices. It is not obvious why no exceptions were found as there are no physical obstacles to applying peak hour restrictions on weekends, or to opening all day HOV lanes to general purpose traffic on weekends.

Nighttime use of HOV lanes
For systems that operate peak period HOV systems, the most common time for opening HOV lanes to general-purpose traffic is 7:00 PM. In the morning the most common start times for HOV operation are 5:00 AM and 6:00 AM. There are scattered examples of peak period facilities that do not restrict general-purpose use of HOV lanes until as late as 7:00 AM. In the Puget Sound area 7:00 AM is well into the morning peak period and HOV lane use is substantial.

The majority of peak period systems open HOV lanes to general-purpose traffic at 9:00 AM. There is greater variation in the afternoons, with peak period HOV restrictions usually going into effect at either 3:00 PM or 4:00 PM. Decisions on HOV lane hours of operation can become complex if the system covers a large area and the facilities are controlled by a number of governmental entities. The San Francisco Bay area has HOV facilities on State Highways, County Expressways and Interstate freeways. The vast majority of these are open to general-purpose traffic from 9:00 AM to 3:00 PM, but there are exceptions. In the east Bay area, hours of operation are different on each of the three Interstate freeway HOV lane segments. This was not a random decision by Caltrans. The HOV hours of operation were established to reflect the peak travel hours for each facility. Since the HOV lanes on those segments of Interstate Highway are not connected to one another, system continuity problems are largely avoided.

HOV lane use in the off-peak direction
Examples of opening HOV lanes to general-purpose traffic in the off-peak direction are rare, though the arterial HOV lanes on Airport Road in Snohomish County fall into this category.

Incident policy
In most regions that have HOV facilities the response to traffic incidents is largely determined on a case-by-case basis by law enforcement officers on the scene. If an incident blocks general-purpose lanes state patrolmen can, and sometimes do, direct traffic into HOV lanes.

There are, however, several regions where specific policies have been adopted regarding use of HOV lanes in the event of accidents that block traffic in the general-purpose lanes. It should be noted that most of the HOV facilities covered by incident use policies are barrier separated or reversible, in some cases both. The operational characteristics of such facilities require carefully controlling access. The formal policies that have been adopted are needed because opening these facilities to general-purpose traffic requires coordination and monitoring at numerous locations over an entire segment, often involving several agencies. This goes far beyond simply directing a line of cars past an accident, as is common practice with HOV lanes that are only separated from other traffic by a paint stripe. In the Puget Sound region the I-90 center roadway and the I-5 reversible lanes function much like the barrier separated HOV facilities covered by the incident policies summarized above.

Following is a brief summary of policies in other regions:

Hampton Roads, Virginia
The Virginia Department of Transportation (VDOT) operates several barrier separated reversible HOV lanes. In 2001 VDOT adopted a policy allowing the HOV lanes to be opened to general-purpose traffic for accidents that block traffic for more than 10 minutes. Initially a five-minute threshold had been requested, but this did not meet with approval from FHWA. VDOT has estimated average time saving of approximately four minutes per vehicle when the HOV lane is opened to general-purpose traffic during incidents.

Dallas, Texas
Dallas has a variety of HOV facilities including concurrent flow freeway HOV lanes, movable barrier and reversible HOV facilities. DART, the transit agency for the Dallas region, has provisions for emergency use of the HOV lanes for general-purpose traffic if there are multiple lane closures due to an incident on the general-purpose lanes.

Houston, Texas
Houston has an extensive network of reversible busways that also allow use by 2+ HOVs. In the event a major incident causes prolonged closure of the freeway mainlines, the HOV lanes may be opened to serve as a freeway lane during operating or non-operating hours. These facilities are managed by the transit agency and METRO Police have primary responsibility for implementing emergency measures. Actions are coordinated through a regional transportation and emergency management center. Variable message signs are used to notify motorists upstream of the incident.