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A History of Reducing Tailpipe Emissions

1970-1975: The First Standards

1977-1988: Tightening Standards for the First Time

1990-1994: Tier One

1998: Voluntary Agreement For Cleaner Cars

1999: Tier Two

Cars

Year 1975 1977 1981 1994 1999 2004-2009
NOx Standard (gpm) 3.1 2.0 1.0 0.6 0.3 0.07
NOx Reduced (from previous standard) 35% 50% 40% 50% 77%

Smaller SUVs, Minivans and Light Trucks: Less that 6000 lbs
Year 1975 1979 1988 1994 1999 2004-2009
NOx Standard (gpm) 3.1 2.3 1.2 0.6 0.5 0.07
NOx Reduced (from previous standard) 26% 48% 50% 17% 86%

Larger SUVs, Vans and Heavier Trucks: Between 6000 and 8500 lbs
Year 1998 1994 2004-2007 2008-2009
NOx Standard (gpm) 1.7 1.53 0.2 0.07
NOx Reduced (from previous standard) 10% 87% 65%
or 95% from 1994 std.

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