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Please note: This summary is provided to help you understand the regulations. Consult the references provided for links to the full text of the regulations.

Transportation Modes » Road » Engine Emissions

Diesel Exhaust Fluid (DEF)	Summary	Full Text
Diesel Fuel Requirements (Truck)	Summary	Full Text
Engine Emissions (Truck, Idling)	Summary	Full Text
Engine Emissions (Nonroad and Auxiliary Equipment)	Summary	Full Text
Engine Emissions (On-board Diagnostics)	Summary	Full Text
Engine Emissions (Truck, Tailpipe)	Summary	Full Text
Engine Tampering	Summary	Full Text
Greenhouse Gas Comparisons	Summary	Full Text
Greenhouse Gas Emissions	Summary	Full Text
LNG Tank Venting	Summary	Full Text
National Clean Diesel Program	Summary	Exit TERC
SmartWay	Summary	Exit TERC
Zero Emission Vehicles	Summary	Full Text

Diesel Exhaust Fluids (DEF)

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Applies to:	Anyone who owns or operates a Diesel powered vehicle that uses a Selective Catalytic Reduction (SCR) system to meet federal engine emissions standards.
Requires:	No additional requirements beyond those applying to engine maintenance and rebuilding -- article provides background and best practices information.
See also:	Clean Air Act Engine Tampering

Diesel Fuel Requirements (Truck)

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Applies to:	Applies directly to vehicle and engine manufacturers and the refining industry, who are required to produce cleaner running engines and diesel fuel. Applies indirectly to the transportation sector by affecting the cost and availability of fuel.
Requires:	Heavy-duty engines must meet emissions standards for particulates (soot) and ozone precursors (nitrogen oxides and hydrocarbons). Diesel fuel must meet limits on sulfur content.
See also:	Clean Air Act National Clean Diesel Campaign (exit TERC)

Engine Emissions (Truck, Idling)

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Applies to:	All trucks operating in or passing through an area where state or local idling ordinances are in force. (There are no federal regulations limiting truck idling. However, more than half of U.S. states and dozens of cities and counties have enacted idling laws or ordinances.)
Requires:	Most frequently, idling laws limit the amount of time, in minutes, that a truck and operate its engine while not moving. Many exemptions apply, which can vary widely among locations and states.
See also:	Engine Emissions (Truck, Tailpipe) Fuel Efficiency Greenhouse Gas Emissions National Clean Diesel Campaign (exit TERC) SmartWay Program (exit TERC)

Engine Emissions (Nonroad and Auxiliary Equipment)

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Applies to:	The standards apply directly to engine and equipment manufacturers, rather than owners and operators. In some cases, owners may be required to register their equipment, and to keep records available for inspection.
Requires:	The standards limit the allowable level of emissions from a wide variety of non-vehicle engines sold in the United States. Some types of engines, such as forklift trucks and transport refrigeration units, are used widely in the transportation sector.
See also:	Clean Air Act Greenhouse Gas Emissions Engine Emissions (Truck, Idling) Engine Emissions (Truck, Tailpipe) National Clean Diesel Campaign (exit TERC)

Engine Emissions (On-board Diagnostics)

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Applies to:	Manufacturers or importers of new heavy-duty vehicles or engines intended for highway use; also applies to anyone who converts heavy-duty vehicles or engines used in highway vehicles to run on alternative fuels
Requires:	Manufacturers must install systems that monitor the functioning of the vehicle or engine emission control system, and that alerts the operator if corrective action is needed
See also:	Engine Emissions (Truck, Idling) Engine Emissions (Truck, Tailpipe) National Clean Diesel Campaign (exit TERC) SmartWay Program (exit TERC)

Engine Emissions (Truck, Tailpipe)

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Applies to:	Emissions standards for new vehicles apply to manufacturers and importers. In many locations, inspection and maintenance regulations, and some operating restrictions, apply to vehicle owners and operators.
Requires:	New vehicles must emit levels of several hazardous pollutants below specified thresholds tested over standard driving cycles. Existing vehicles registered or operating in specified locations must be inspected periodically. Some states have instituted roadside monitoring programs to detect and test for smoke opacity. Idling restrictions apply in some locations.
See also:	Alternative Fuels Biodiesel Clean Air Act Diesel Fuel Requirements (Truck) Engine Emissions (Truck, Idling) Greenhouse Gas Emissions National Clean Diesel Campaign (exit TERC) SmartWay Program (exit TERC)

Engine Tampering

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Applies to:	Anyone who is rebuilding or modifying a heavy-duty highway diesel engine from model year 2004 or later
Requires:	The rebuilt engine must continue to meet the same emissions standards as those that applied to the engine when new, and the owner must maintain records of work performed and other specified information for at least two years.
See also:	Clean Air Act Engine Emissions (Truck, Idling) Engine Emissions (Truck, Tailpipe) Fuel Efficiency Greenhouse Gas Emissions National Clean Diesel Campaign (exit TERC) SmartWay Program (exit TERC)

Greenhouse Gas Comparisons

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Applies to:	Any vehicle
Requires:	Calculators based on emission factors provide a useful but limited way to compare the greenhouse gas emissions of transportation modes
See also:	Best Speed for Fuel Economy Greenhouse Gas Emissions

Greenhouse Gas Emissions

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Applies to:	Applies directly to vehicle and engine manufacturers. Applies indirectly to the transportation sector by affecting the cost and performance of vehicles.
Requires:	Rule requires manufacturers to certify that new Class 7 and 8 combination tractors, and many heavy-duty special purpose vehicles, meet fuel efficiency and greenhouse gas emissions standards.
See also:	Clean Air Act Engine Emissions (Truck, Idling) Engine Emissions (Truck, Tailpipe) Fuel Efficiency SmartWay Program (exit TERC)

LNG Tank Venting

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Applies to:	All liquefied natural gas (LNG) fuel tanks
Requires:	Both fuel level and internal tank temperature must be known to calculate how long an LNG tank can avoid venting fuel to the atmosphere.
See also:	Alternative Fuels Greenhouse Gas Emissions

National Clean Diesel Campaign (exit TERC)

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Applies to:	EPA's National Clean Diesel Campaign (NCDC) promotes clean air strategies by working with manufacturers, fleet operators, air quality professionals, environmental and community organizations, and state and local officials to reduce diesel emissions
Requires:	Recent diesel rulemakings have focused on light- and heavy-duty highway vehicles, nonroad diesel equipment, locomotive and marine engines, and large ocean-going vessels
See also:	SmartWay Program (exit TERC)

SmartWay Program (exit TERC)

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Applies to:	Shippers, truck and rail transporters, logistics companies, truck stop operators, and others
Requires:	SmartWay is a voluntary program that provides resources to help achieve fuel efficiency improvements and emissions reduction, and identifies products and services that reduce transportation-related emissions
See also:	Greenhouse Gas Emissions National Clean Diesel Campaign (exit TERC) Engine Emissions (Truck, Tailpipe)

Zero Emission Vehicles

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Applies to:	Proposed rule applies to manufacturers, sellers, and importers of light and heavy duty vehicles.
Requires:	Emission rates of greenhouse gases per unit of work performed, averaged over a seller’s entire fleet of vehicles sold, must fall within set limits for each type of vehicle. Limits have been proposed for model years 2027 through 2032, becoming stricter each year as low and zero emission vehicles become more widely available and affordable.
See also:	Greenhouse Gas Emissions Alternative Fuels Engine Emissions (Truck, Tailpipe)

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