California's Low Emission Vehicle (LEV) program defines automotive emission standards which are stricter than the United States' national "Tier" regulations. There have been two major phases. The first began in the 1990s and ended when the Low Emission Vehicle II (LEV II) standards began to be phased in for 2004. Several states other than California now use the same restrictions. These include Maine, Massachusetts, New York, Oregon, Vermont, and Washington and are frequently referred to as "CARB states" in automotive discussions since the regulations are defined by the California Air Resources Board.
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