TABLE 4-1 Types of Vehicles and Engines Regulated by AQM in the United States

Source Category

Status (Date Promulgated; Effective Date)

On-road sources


Light-duty vehicles (LDVs or passenger cars)

Tier 2 regulations require about 99% reduction over previous control levels for cars (2000; 2004–2007)

Light-duty trucks (LDTs) (pickup trucks, minivans, passenger vans, and sport-utility vehicles with a gross weight of less than 8500 lb)

Must comply with Tier 2

Lightest truck (2000; 2004–2007)

Heavier light trucks (2000; 2008–2009)

Medium-duty passenger vehicles (MDPVs) (vehicles with gross weight 8,500–10,000 used for personal transportation, such as larger sport utility vehicles [SUVs] and passenger vans)

Tier 2 standards to be phased in beginning with the 2008 model year (2000; 2008–2009)

Heavy-duty vehicles (HDVs) (vehicles with gross weight greater than 8500 lb used commercially, such as large pickups, buses, delivery trucks, recreational vehicles [RVs], and semi-trucks.

Highway Heavy-Duty Rule requires new vehicles to meet substantially lower PM and NOx standards (>90% reduction) (2001; 2007–2010)

Also strict fuel sulfur levels (15 ppm) (2001; 2006)


New standards to reduce emissions by 80% (based on California) (proposed 2002; to take effect 2006–2010)

Nonroad Sources


Nonroad, spark ignition (gasoline) engines

For handheld engines, new rules require 70% NOx plus hydrocarbon reduction (2000; 2002–2007)

New standards promulgated for larger spark ignition engines (2002; 2004–2007)

Nonroad recreational vehicles and engines

New rules for variety promulgated to require between 55% and 80% reduction in emissions (depending on pollutant) (2002; 2006–2009, depending on type of engine)

Nonroad compression ignition (diesel) engines

Nine size ranges, including agricultural and construction equipment; existing rules promulgated in 1998 (1998; 1999–2008)

New standards comparable to Highway Heavy Duty Rule proposed 2003

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