CARB

The first definition has its origin in the California ZEV rule, adopted as part of the 1990 Low-Emission Vehicle (LEV I) Program mandated by CARB. The ZEV regulation has evolved and been modified.

several times since 1990. Several new partial or low-emission categories were created and defined as follows: 

•   LEV (Low Emission Vehicle): The least stringent emission standard for all new cars sold in California beyond 2004.
• ULEV (Ultra Low Emission Vehicle): 50% cleaner than the average new 2003 model year vehicle.
• SULEV (Super Ultra Low Emission Vehicle): These vehicles emit substantially lower levels of hydrocarbons, carbon monoxide, oxides of nitrogen and particulate matter than conventional vehicles. They are 90% cleaner than the average new 2003 model year vehicle.
•  PZEV (Partial Zero Emission Vehicle): Meets SULEV tailpipe standards, has a 15-year / 150,000 mile warranty, and zero evaporative emissions. These vehicles are 80% cleaner than the average 2002 model year car.
• AT PZEV (Advanced Technology PZEV): These are advanced technology vehicles that meet PZEV standards and include ZEV enabling technology. They are 80% cleaner than the average 2002 model year car.
• ZEV (Zero Emission Vehicle): Zero tailpipe emissions, and 98% cleaner than the average new 2003 model year vehicle.
   
  The Low-Emission Vehicle Program is currently under revision to define modified ZEV regulations for 2015 models.