AT-PZEV is an acronym for Advanced Technology Partial Zero Emissions Vehicle. These are vehicles that meet the SULEV and PZEV tailpipe emissions requirements, but also include components on the cutting edge of technology that help to improve the fuel mileage of PZEVs. Hybrid drivetrain components are a good example. PZEVs run on gasoline, yet offer extremely clean emissions with zero evaporative emissions.
PZEVs come by way of California's Zero Emission Vehicle (ZEV) mandate, a vital portion of the state's low emission vehicle program dating back to 1990. Throughout history, CA has set a tight green benchmark for stringent emissions laws that have in turn led to tighter federal regulations. Vehicles are required to meet tight emission test requirements for volatile organic compounds (VOC), oxides of nitrogen (NOx), and carbon monoxide (CO). While it was thought that battery electric vehicles would be numerous on roads by now, problems from cost to range--and even marketing issues--led to a modification of the ZEV mandate that gave birth to the PZEV--the partial zero emissions vehicle which allows automakers to meet their quotas through partial zero credits.