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A partial zero emissions vehicle is a vehicle that has zero evaporative emissions from its fuel system, has a 15-year (or at least 150,000-mile) warranty on its emission-control components, and meets SULEV tailpipe-emission standards.
PZEVs have their own administrative category within the state of California for low emission vehicles.
This vehicle category was created as part of a bargain with the California Air Resources Board (CARB), so that the automobile manufacturers could postpone producing mandated zero emission vehicles (ZEVs), which will require the production of electric vehicles or hydrogen fuel cell vehicles.
The vehicles constructed to meet the PZEV requirements must achieve both SULEV (Super Ultra Low Emission Vehicle) exhaust emissions and zero evaporative (fuel system) emissions. The SULEV standard is designed to be even more rigorous than the Ultra standard or low-emission vehicle standard. Various techniques are used to reduce pollution in these vehicles. All emissions-related components must be warrantied for 15-years or 150,000-miles. This includes the electric propulsion components of a hybrid electric vehicle.
Some vehicles can be classified as AT-PZEV, standing for Advanced Technology PZEV. This type of vehicle is at least as clean as a PZEV vehicle, and either uses NO gasoline (such as the Honda Civic GX natural gas vehicle) or gets much better fuel efficiency due to the use of hybrid electric vehicle systems. This technology can be used in Sport Utility Vehicles to improve their traditionally lower fuel economy; however they may still lag behind the fuel economy of smaller vehicles.
CARB also prepared a TZEV (Transitional ZEV, formerly Enhanced AT-PZEV) category for plug-in hybrids (PHEVs) and hydrogen vehicles. (Not to be confused with Hydrogen Fuel Cell Electric Vehicles which are certified as ZEV or Zero Emission Vehicles) In addition to the 15 year or 150,000 mile warranty for zero evaporative (fuel system) emissions, and SULEV tailpipe emissions, PHEVs must also warranty their traction battery for 10 years or 150,000 miles. While PHEVs and hydrogen internal combustion engine vehicles exist, none meet this stringent standard.
With the exception of some hybrids and alternative-fuel vehicles, PZEVs do not inherently offer consumers any incentives other than the extended emissions warranty. In particular, PZEV vehicles do not automatically qualify for the hybrid vehicle tax credit or for the "clean air vehicle" decal that used to allow hybrid car drivers to use car-pool lanes.
PZEVs do, however, provide benefits to the originating automaker in the form of ZEV credits. Automakers must have a certain number of ZEV credits based on the number of vehicles they sell annually in California, with exceptions granted for small volume manufacturers. Without ZEV credits, automakers cannot sell in California. Automakers with excess credits can sell them. No automaker has ever missed compliance.
Originally, vehicles that meet PZEV standards were only available in California, Maine, Massachusetts, New York, Oregon, or Vermont and in Canada— or in some sales regions near these states. These six "clean car states" had implemented California's more stringent motor vehicle pollution control rules. Other states soon began implementing these standards, including Alaska, Connecticut, Maryland, New Jersey, Pennsylvania, Rhode Island, and Washington, and PZEVs are now widely available in the United States.