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Frequent Questions
  1. Do those products that claim to improve fuel economy or lower emissions really work?
  2. How can I get a copy of the Certificate of Conformity for my car?
  3. Why is my gas mileage lower than the EPA rating?

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What's New in OTAQ
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OTAQ Recent Additions

  • July 17: EPA is currently conducting adequacy reviews of PM2.5 redesignation and maintenance plan for Cincinnati - Hamilton Area, KY Portion.
  • June 25: EPA has updated the 2011 I/M OBD Readiness Testability Issues List to correct its OBD testing guidance for model year 1996-98 Mitsubishi vehicles.
  • June 15: EPA approved the first plans for satisfying the misfueling mitigation conditions of the E15 partial waivers.

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OTAQ Press Releases

  • June 27, 2012: EPA Agreement with BASF Corp. on Air Pollution from Wyandotte Plant Brings Clean Diesel Project to Wayne County
  • May 10, 2012: EPA Updates Clean Air Act Requirements for Gas Stations to Reflect New Vehicle Technologies / Widespread use of advanced vehicle technologies capture harmful gasoline vapors when refueling, delivering more cost-effective emissions reductions
  • April 23, 2012: $20 Million Available for Clean Diesel Projects

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OTAQ Federal Register Notices

  • July 20, 2012 : Agency Information Collection Activities; Submission to OMB for Review and Approval; Comment Request; Exclusion Determinations for New Nonroad Spark-Ignited Engines, New Nonroad Compression-Ignited Engines, and New On-Road Heavy Duty Engines (Renewal)
  • July 20, 2012: Agency Information Collection Activities; Submission to OMB for Review and Approval; Comment Request; Nonconformance Penalties for Heavy-Duty Engines and Heavy-Duty Vehicles, Including Light-Duty Trucks (Renewal)
  • June 18, 2012: Control of Air Pollution From Aircraft and Aircraft Engines; Emission Standards and Test Procedures

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EPA's Office of Transportation and Air Quality protects public health and the environment by regulating air pollution from motor vehicles, engines, and the fuels used to operate them, and by encouraging travel choices that minimize emissions. These "mobile sources" include cars and light trucks, heavy trucks and buses, nonroad engines, equipment, and vehicles. For more information see:


OTAQ's top sites

The Green Vehicle Guide


National Clean Diesel Campaign

OTAQ's programs and website topics (A detailed list of programs and topics is on our site map.)

Overview:  Pollutants & Programs

Overview:  Pollutants and Programs

Information on how much air pollution, air toxics, and greenhouse gases are emitted by mobile sources, the programs OTAQ has undertaken to control these emissions, and the impact of those programs on air quality and climate change.

- Air Toxics
- Mobile Sources
- Transportation & Climate

Consumer Information

Consumer Information

Learn what you can do to help reduce air pollution. Use the Green Vehicle Guide to find the cleanest, most fuel-efficient vehicle that meets your needs.

- What You Can Do
- Green Vehicle Guide

On-Road Vehicles & Engines

On-Road Vehicles and Engines

Information about fuel economy, emission standards and regulations, emission recall, certification and compliance, inspection and maintenance, diesel retrofit, evaluating the benefits of inventions designed to reduce emissions, and importing vehicles and engines.

- Cars & Light Trucks
- Heavy Trucks, Buses & Engines
- Motorcycles
- Importing Vehicles & Engines

Nonroad Engines, Equipment
& Vehicles

Nonroad Engines, Equipment and Vehicles

Information about nonroad engines, equipment and vehicles: emission standards and regulations, certification and compliance, and diesel retrofit programs.

- Aircraft
- Diesel Boats & Ships
- Gasoline Boats & Personal Watercraft
- Nonroad Diesel Equipment
- Forklifts, Generators & Compressors
- Lawn & Garden
- Locomotives
- Snowmobiles, Dirt Bikes, & ATVs

Fuels & Fuel Additives

Fuels and Fuel Additives

Information on fuels for mobile sources, fuel-quality control programs, requirements for registration and health effects testing of new fuels or fuel additives, and reporting forms.

- Renewable & Alternative Fuels
- Gasoline
- Diesel
- Compliance



Information about our partnerships to reduce air pollution associated with transportation and other mobile sources.

- National Clean Diesel Campaign
- SmartWay
- Clean School Bus USA

State & Local Transportation

State and Local Transportation Resources

Information on the ties between land use, transportation planning, and air quality.

- Transportation Conformity
- Policy & Guidance
- Laws & Regulations
- Calculators & Tools

Modeling, Testing, & Research

Modeling, Testing, and Research

Information on modeling and inventories for estimating emissions from highway vehicles, nonroad sources, and fuels; testing and measuring emissions; research into clean automotive technologies; and emission factors research.

- Modeling & Inventories
- Testing & Measuring Emissions
- Clean Automotive Technologies
- Emission Factors Research

This page is maintained by EPA's Office of Transportation and Air Quality (OTAQ).
For more: About Us | Get Email Updates | Browse the A to Z Subject Index.

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