Beginning in the 2004 model year, new EPA emission requirements, known as "Tier 2", have officially taken effect. The requirements include the most stringent Federal emission standards ever. In 2004, manufacturers of cars and the smaller trucks are required to certify 25% of their fleet to meet Tier 2 standards. In fact, for Model Year 2004, more clean vehicles will be sold than the EPA program requires, thanks to the efforts of the automotive industry. The phase-in continues over the next few years, and by 2009, 100% of all cars and light trucks must meet the standards. Along with the Tier 2 standards, California's strict "LEV II" standards are also taking effect. The new Federal and California standards are having a large effect on the emissions scores for 2004 models. For instance, the Green Vehicle Guide Scores for all vehicles have increased on average from 4 in 2003 to 6 in 2004.

Also being phased in with the Tier 2 emission standards are requirements for cleaner burning low-sulfur fuel. The combination of cleaner fuel and cleaner vehicles will result in significant emission reductions for the nation.

                                                               From EPA