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Federal-Aid Highway Program Guidance on High Occupancy Vehicle (HOV) Lanes
September 2016

Glossary of Terms

Alternate fuel vehicle – A vehicle that is operating on (1) methanol, denatured ethanol, or other alcohol; (2) a mixture containing at least 85 percent of methanol, denatured ethanol, and other alcohols by volume with gasoline or other fuel; (3) natural gas; (4) liquefied petroleum gas; (5) hydrogen; (6) coal derived liquid fuels; (7) fuels (except alcohol) derived from biological materials; (8) electricity (including solar energy); or (9) any other fuel that the Secretary prescribes by regulation that is not substantially petroleum and that would yield substantial energy security and environmental benefits, including fuels regulated under 10 CFR 490.

Auxiliary Lane – FHWA deems this term to have the same meaning as in the American Association of State Highways and Transportation Officials (AASHTO) Policy on Geometric Design of Highways and Streets, 2001 (commonly, the "Green Book") as the portion of roadway adjoining the traveled way, and designated for speed change, turning, storage for turning, weaving, truck climbing, and other purposes supplementary to through-traffic movement.

High Occupancy Vehicle (HOV) – Federal law defines a "high occupancy vehicle" or "HOV" to mean a vehicle with no fewer than two persons.

HOT lane – "High Occupancy/Toll" lane means any HOV lane that allows vehicles not meeting minimum occupancy requirement to use the lane by paying a toll.

HOV facility – "High Occupancy Vehicle" facility; One that gives priority treatment to buses, vanpools, carpools and high-occupancy vehicles, including the HOV lanes, the park-and-ride lots, and other support facilities or elements.

HOV lane – Any preferential lane designated for exclusive use by vehicles with 2 or more occupants for all or part of a day, including a designated lane on a freeway, other highway or a street, or independent roadway on a separate right-of-way.

HOV system – Any coordinated region wide network of integrated HOV facilities.

Initial Construction – Federal law defines "initial construction" as the construction of a highway, bridge, tunnel, or other facility before it is open to traffic. Conversely, and intentionally, the definition excludes any improvement to a highway, bridge, tunnel or other facility after it is open to traffic.

Inherently Low Emission Vehicles (ILEV) – Any kind of vehicle which, because of the inherent properties of the fuel system design will not have significant evaporative emissions, even if its evaporative emission control system has failed. These vehicles are certified by the Environmental Protection Agency pursuant to 40 CFR 88.311-93 and labeled pursuant to 40 CFR 88.312.93.

Low Emission & Energy-Efficient Vehicles – A vehicle that has been certified as meeting the Tier II emission level under section 202(i) of the Clean Air Act (42 U.S.C. 7521 (i)) for that make and model year and is certified by EPA to have achieved not less than a 50-percent increase in city fuel economy or not less than a 25 percent increase in combined city-highway fuel economy relative to a comparable vehicle that is an internal combustion gasoline fueled vehicle; or is an alternative fuel vehicle; or is an alternative fuel vehicle.

Occupancy requirement – Any restriction that specifies a minimum number of persons in a vehicle. For example, HOV lanes are often 2+ (the driver plus one or more passengers) or 3+ (the driver plus two or more passengers) to use that lane. For purposes of this definition, fetuses in the womb do not constitute an occupant in the vehicle.

Public Authority – Federal law defines "public authority" as a State, interstate compact of States, or public entity designated by a State.

Public transportation vehicle – A vehicle that that (1) provides designated public transportation as defined in Section 221 of the Americans with Disabilities Act of 1990 (42 U.S.C. 12141) or provides public school transportation (i.e. to and from public or private primary, secondary, or tertiary schools); and (2) is owned or operated by a public agency entity; or is operated under a contract with a public agency entity; or is operated pursuant to a license by the Secretary or a State agency to provide motorbus or school vehicle transportation services to the public. For purposes of HOV and HOT travel, this would include said vehicles that are deadheading (i.e., no passengers, only a driver) and would not otherwise be subject to occupancy minimums.

Reconstruction – major work necessary to bring a facility up to (i.e., to improve to) an acceptable level of service. Such work may include, but is not limited to, the replacement of the pavement structural section, modernization of interchanges, adding interchanges, upgrading structural safety features, replacement of bridge decks and bridge parapets, adjustments to vertical and horizontal alignment, adding full-width and/ or full-depth shoulders, grade separations, and strengthening bridges to accommodate greater loads.

Single Occupancy Vehicle (SOV) – Any motor vehicle not meeting the established occupancy requirement of a HOV lane. While it is possible for a vehicle with more than one occupant to not meet the occupancy requirement if the standard is established at more than two persons, the term SOV is used to encompass all such vehicles not meeting the occupancy requirement.

Tier II Emission – The Tier II emission level established in regulations prescribed by the Environmental Protection Agency under section 202(i) of the Clean Air Act for that vehicle's make, model, and model year. The Tier II emission standards are based on a system of emission bins in which light-duty vehicles and light-duty trucks are certified in one of the eight bins; Bin 1 represents the cleanest or lowest emitting vehicles, and Bin 8 represents the highest emitting vehicles of the Tier II bins.

Toll Facility – Federal law defines "toll facility" as a toll highway, bridge, or tunnel, or approaches to same, that are constructed under 23 U.S.C. 129(a).

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