NOx grams per mile
| Year | Automobile | Light Truck |
|---|---|---|
| 1966 | 4.1 | 3.6 |
| 1967 | 4.1 | 3.6 |
| 1968 | 4.1 | 3.6 |
| 1969 | 4.1 | 3.6 |
| 1970 | 4.1 | 3.6 |
| 1971 | 4.1 | 3.6 |
| 1972 | 3.1 | 3.6 |
| 1973 | 3.1 | 3.6 |
| 1974 | 3.1 | 3.6 |
| 1975 | 3.1 | 3.1 |
| 1976 | 3.1 | 3.1 |
| 1977 | 2 | 3.1 |
| 1978 | 2 | 3.1 |
| 1979 | 2 | 2.3 |
| 1980 | 2 | 2.3 |
| 1981 | 1 | 2.3 |
| 1982 | 1 | 2.3 |
| 1983 | 1 | 2.3 |
| 1984 | 1 | 2.3 |
| 1985 | 1 | 2.3 |
| 1986 | 1 | 2.3 |
| 1987 | 1 | 2.3 |
| 1988 | 1 | 1.2 |
| 1989 | 1 | 1.2 |
| 1990 | 1 | 1.2 |
| 1991 | 1 | 1.2 |
| 1992 | 1 | 1.2 |
| 1993 | 1 | 1.2 |
| 1994 | 0.4 | 1.2 |
| 1995 | 0.4 | 0.4 |
| 1996 | 0.4 | 0.4 |
| 1997 | 0.4 | 0.4 |
| 1998 | 0.4 | 0.4 |
| 1999 | 0.4 | 0.4 |
| 2000 | 0.4 | 0.4 |
| 2001 | 0.4 | 0.4 |
| 2002 | 0.4 | 0.4 |
| 2003 | 0.4 | 0.4 |
| 2004 | 0.4 | 0.4 |
| 2005 | 0.07 | 0.07 |
| 2006 | 0.07 | 0.07 |
| 2007 | 0.07 | 0.07 |
| 2008 | 0.07 | 0.07 |
| 2009 | 0.07 | 0.07 |
