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Mobile Sources and Transportation Program

Mobile Sources are responsible for a significant percentage of pollutants that are managed by the Clean Air Act. Under the Clean Air Act, the US Environmental Protection Agency (US EPA) established National Ambient Air Quality Standards (NAAQS) for criteria pollutants that adversely impact public health. The three major transportation-related criteria air pollutants are:

The pollutants from mobile sources are harmful to public health and create haze that reduces visibility. Motor vehicles are also sources of hazardous air pollutants. Over the past 21 years, Utah's motor vehicle emissions inspection and maintenance (I/M) programs have been one of the major successful control strategies that have led to attainment of the National Ambient Air Quality Standards (NAAQS) along the Wasatch Front. Utah's I/M programs are administered by the local health departments in Davis, Salt Lake, Utah and Weber Counties in coordination with the Mobile Sources and Transportation Section. The section also works closely with the Utah Department of Transportation (UDOT) and regional Metropolitan Planning Organizations (MPOs) in transportation planning and air quality modeling. Mobile sources include both on-road and off-road sources.

Examples of On-road and Off-road Sources


  • Cars
  • Trucks
  • Buses
  • Motorcycles


  • Construction, mining, agriculture and logging equipment
  • Aircraft and associated ground support equipment
  • Locomotives
  • Pleasure craft and commercial marine vessels
  • Lawn and garden care equipment

The Division of Air Quality is committed to public outreach and education through its integrated activities with the National Center for Automotive Science & Technology (NCAST) at Weber State University in Ogden, Utah. The Center provides an innovative partnership among government, education, and industry in applied research and education in vehicle emissions technology and related education. The CAST hosts the National On-Board Diagnostics (OBD) Clearinghouse and conducts advanced vehicle emissions-related training courses for I/M administrators, vehicle technicians and automotive industry representatives.

Recent advances in vehicle and fuel technologies have dramatically reduced emissions throughout a vehicle's life. Additional reductions in vehicle emissions are anticipated over the next few years, as new Federal vehicle and fuel standards are implemented and assimilated into the vehicle fleet. However, due to population growth and increased driving, on-road and off road vehicles continue to be responsible for nearly half the air pollution in Utah. Over the past several years, the US Environmental Protection Agency (USEPA) has adopted more stringent National Ambient Air Quality Standards (NAAQS) for fine particulates and ozone. The USEPA is considering even more stringent air quality standards to protect the public's health. These more rigorous air quality standards will be difficult to achieve in Utah's urbanized and rapidly-growing rural areas.

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For general information or questions contact


  • General Information or Questions, Contact Joe Thomas (801) 536-4175