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4.0 Issues/Considerations With Hybrid Vehicle Use of HOV/HOT Lanes

The experiences from states allowing hybrids and/or AFVs to access HOV and HOT lanes without meeting vehicle-occupancy requirements provide insight into possible issues that may be encountered with these programs. As highlighted in this section, these issues include creating congestion in the HOV/HOT lanes, reducing carpooling, causing confusion among user groups, addressing hybrid vehicles from other states, determining the eligible hybrid and AFVs, and expanding HOV lanes to HOT lanes. Consideration of these issues and possible approaches to address them prior to allowing hybrid access is important. Communicating this information to hybrid owners, other HOV/HOT users, and policy makers is also important to provide realistic expectations if changes in operations or user groups need to be made.

  • Congestion in the HOV/HOT Lanes. The addition of hybrid vehicles to HOV/HOT lanes already operating at or near capacity may cause congestion and reduce the travel-time savings and trip-time reliability historically provided to HOVs – buses, vanpools, and carpools. MAP-21 requires that state agencies demonstrate that an HOV facility is not already degraded and that the pressure of low-emission and energy-efficient vehicles will not cause the facility to become degraded. They must also report annually on HOV lane use and develop mitigation plans to address any degradation. In Virginia, this issue occurred and was initially addressed by legislation establishing new clean special fuel license plates, which limited access to individual HOV facilities based on the different license plates. Further, both California and Virginia have developed degrading mitigation plans to address specific concerns with allowing these vehicles to access HOV lanes in both states.
  • Reducing Carpooling. Current carpoolers who can afford to purchase a hybrid vehicle may do so solely to use an HOV/HOT lane, thus diminishing the intent of supporting carpooling. While no formal surveys have been conducted documenting existing carpoolers, vanpoolers, or bus riders purchasing hybrid vehicles primarily to use HOV/HOT lanes, the trends on the LIE indicates that carpool use of the HOV lanes has decreased while permits for hybrid vehicles have increased. The purchase of hybrid vehicles and applications for clean special fuel license plates are much higher in northern Virginia than in the Hampton Roads area, and use of the HOV lanes in northern Virginia by drivers of hybrid vehicles is much higher than the HOV lanes in Hampton Roads.
  • Causing Confusion among User Groups. Changing requirements for use of HOV/HOT lanes by hybrid vehicle owners may cause confusion among different user groups. Changing the clean special fuel license plate designs and limiting access to different HOV lanes in northern Virginia adds complexity to the program and may make it more difficult for users to understand. The Dr. Gridlock column in the Washington Post has addressed questions from individuals purchasing or thinking of purchasing a hybrid vehicle, only to find out that they are not able to use the HOV lanes on I-95, I-395, and I-66.
  • Hybrid Vehicles from Other States. The HOV/HOT lanes in some areas, such as northern Virginia and New York, are very close to adjacent states and may serve multi-state travel patterns. Residents owning qualifying hybrid vehicles in adjacent states have questioned why they are not allowed to use these HOV/HOT lanes. For example, the Maryland State Highway Administration HOV website warns that hybrid vehicles with Maryland license plates are not allowed to use the HOV lanes in Virginia. Non-New York residents have written their congressmen questioning why out-of-state hybrid vehicle owners are not allowed to use the LIE HOV lanes.
  • Establishing Hybrid Vehicle Eligibility. While the EPA and additional state requirements provide guidelines for establishing hybrid vehicle eligibility, vehicle manufacturers and owners have challenged these guidelines and test procedures when their vehicles were not deemed eligible. For example, there has been disagreement over the Chevy Volt not being classified as eligible for the Clean Pass pilot program on the LIE in New York. GM and Volt owners have argued that the emissions and fuel economy was not tested in the way many people actually drive the Volt. The Volt operates solely on electricity for the first 40 miles. The gasoline engine begins powering the vehicle after 40 miles. Individuals driving the Volt for less than 40 miles and recharging it before their next trip, argue it never uses gasoline, and thus never generates any emissions. As a result, they argue, that the Volt is effectively an “all electric” vehicle and should be classified as eligible.
  • HOV Lane to HOT Lane Expansion. The “free pass” given to hybrid vehicles in HOV lanes may be an issue when those HOV lanes are expanded to HOT lanes. Similarly, the development of new HOT lanes in states allowing hybrid access to HOV lanes may present issues. HOT lanes introduce toll collection, and thus, introduce elements of revenue generation. Allowing hybrid vehicles to use HOT lanes without paying the toll reduces revenues, while increasing vehicle volumes. For example, qualifying hybrids are currently able to access the I-95 Express Lanes in Miami, the I-25 Express Lanes in Denver, and the I-15 Express Lanes in Salt Lake City, which are all HOT lanes, without paying a toll or meeting the vehicle-occupancy requirements. Qualifying hybrid vehicles were allowed to use the previous HOV lanes on I-95 and I-15, while the program allowing qualifying hybrids to use the I-15 Express Lanes, as well as HOV lanes in Denver, was initiated after the expansion to HOT lanes. In another example, vehicles with white and green clean air vehicle stickers in California can use the I-25 HOT lanes in San Diego and the I-680 HOT lanes in the Bay Area without paying a toll. Vehicles with AFV license plates and tags are allowed to use the I-85 Express Lanes in Atlanta. In all of these cases, the potential loss of revenues is weighed against the state’s initiatives to encourage the sale and use of environmentally-friendly vehicles.


Other exempt vehicles are allowed to use HOV, HOT, and managed lanes in most states. These typically include public transit buses with only the driver and marked (rooftop emergency lights and sirens) law enforcement and emergency vehicles with only the driver.

Public transit buses carrying passengers are important elements of most HOV, HOT, and managed lanes. Buses are carrying more people in fewer vehicles, adding to the people-moving capacity of HOV, HOT, and managed lanes. Public transit buses with only the driver, which are typically dead-heading or out of service to begin or end service, are allowed to use most HOV, HOT, and managed lanes. This approach provides operating efficiencies and cost savings to the transit agencies and improved service for riders. Issues may arise, however, if taxicabs, airport shuttles, and other private transportation vehicles request the same access. No HOV, HOT, or managed lanes were identified in the literature review allowing these types of vehicles without meeting the occupancy requirement or paying a toll.

Marked law enforcement and emergency vehicles, which typically include police, sheriff, state patrol, EMS, and other related vehicles, are allowed to use most HOV, HOT, and managed lanes without meeting the occupancy requirements. The use of HOV facilities by marked law enforcement and emergency vehicles appears to be relatively low and does not appear to be monitored.

The use of HOV, HOT, and managed lanes by unmarked law enforcement and emergency vehicles or by law enforcement and emergency personnel traveling in their own vehicles was an issue on the HOV lanes in northern Virginia in the early 2000s. The Code of Virginia provides an HOV exemption for law enforcement, but no specific definition of a law enforcement vehicle is provided in the state statute. The Virginia HOV Enforcement Task Force noted issues with the use of HOV lanes in northern Virginia by off-duty law enforcement and emergency personnel, as well as federal employees who consider themselves law enforcement personnel, traveling to and from work in their personal vehicles. Although the Task Force was not able to determine the number of these individuals, it recommended that the statute be better defined and that an education and outreach effort be undertaken focused on these individuals. Outreach efforts were initiated which appear to have helped address the issue.


The purpose of this report was to review the programs in use by states allowing low-emission and energy efficient vehicles, and other exempt vehicles, access to HOV, HOT, and managed lanes without meeting the vehicle-occupancy requirements. Possible issues to consider with allowing low-emission and energy efficient vehicles to use HOV, HOT, and managed lanes was summarized. MAP-21 regulations require that states must submit a report that the facility is not already degraded, and that the presence of the vehicles will not allow the facility to become degraded are discussed, along with the requirement for ongoing monitoring and certification that the facilities meet the operating requirements.

The report should be of benefit to personnel responsible for planning and operating HOV, HOT, and managed lanes, as well as policy makers. The variety of approaches being used by states, and the differences in impacts, should be of interest to others considering new programs or changes in existing programs. The information highlights that states have the authority to develop programs that best meet their needs within the oversight provided by MAP-21 and the federal government.

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