GREET and AFLEET Model Guide

GREET 2020 Release

The Argonne National Laboratory’s Systems Assessment Center is pleased to announce the 2020 release of the suite of GREET Models. Please read Summary of Expansions and Updates in GREET® 2020 (554KB pdf) for more details on updates in this version.

GREET Excel Model: 

  • Fuel-Cycle Model: To download GREET_1_2020 please use the following link GREET 1 Series
  • Vehicle-Cycle Model: To download GREET_2_2020 please use the following link GREET 2 Series


The Department of Energy’s Clean Cities Program has enlisted the expertise of Argonne to develop a tool to examine both the environmental and economic costs and benefits of alternative fuel and advanced vehicles. Argonne has developed the Alternative Fuel Life-Cycle Environmental and Economic Transportation (AFLEET) Tool for Clean Cities stakeholders to estimate petroleum use, greenhouse gas emissions, air pollutant emissions, and cost of ownership of light-duty and heavy-duty vehicles using simple spreadsheet inputs.

The tool uses data from Argonne’s Greenhouse gases, Regulated Emissions, and Energy use in Technologies (GREET) fuel-cycle model to generate necessary well-to-wheels petroleum use and GHG emission co-efficients for key fuel production pathways and vehicle types. In addition, Environmental Protection Agency’s MOtor Vehicle Emission Simulator (MOVES) and certification data are used to estimate tailpipe air pollutant emissions. Various sources are used to provide default cost data, including the Clean Cities Alternative Fuel Price Report and American Recovery and Reinvestment Act awards.

Download tool and documentation

Salt Lake County Vehicle Repair and Replacement Assistance Program (VRRAP)

Vehicle Emissions Program

Salt Lake County Health Department


Vehicle Repair Assistance Program (VRAP)

Depending on the age and overall condition of a vehicle failing the emissions test, low-income vehicle owners may qualify for vehicle repair assistance. We require a completed application and supporting documentation.


Before you may register a motor vehicle (either gasoline or diesel-powered) for operation in Salt Lake County, it must pass an emissions test.

  • Vehicles less than six years old are tested every other year.
  • Vehicles more than six years old must be tested every year.
  • Farm-plated vehicles and vehicles of model year 1967 or older are exempt from testing.

Independent testing facilities located throughout Salt Lake County perform the emissions testing. The  Vehicle Emissions Program licenses and regulates the facilities.

A malfunctioning vehicle can emit one hundred times the amount of pollution that it would if it were working properly.

Every day, the program keeps tons of pollutants out of the Salt Lake Valley’s air:

  • 82 tons of carbon monoxide (CO)
  • 4 tons of hydrocarbons (HC)
  • 4 tons of nitrogen oxide (NOx)


Motor vehicles are responsible for more than 70% of the air pollution that affects our health. When a vehicle is operating properly, its emissions levels are very low. However, a malfunctioning vehicle can emit one hundred times the amount of pollution that it would if it were working properly. Properly tuned and well-maintained vehicles also provide better performance and fuel economy for the owner.

If your vehicle fails the emissions test:

  • Use a repair facility and technician who is familiar with your vehicle and its emissions system.
  • Secure a written estimate that includes diagnosis and recommended repairs.
  • If you are not satisfied with the estimate or diagnosis, get a second technician’s opinion or contact the Air Quality Bureau.
  • Check your vehicle owner’s manual for information specific to your vehicle. Many emissions systems are covered by warranties, if still applicable.

You cannot register a failing vehicle in Salt Lake County until it is properly repaired, retested, and passes the test.


In very rare cases, vehicle owners have made repairs toward the major cause of the high emissions and those repairs have failed to reduce the pollution levels to below the standard. In some of those cases, SLCoHD may issue a repair waiver to allow a failing vehicle to be registered for that year.

A vehicle may qualify for a waiver if it has:

  • failed at least two emissions inspections.
  • received emissions-related repairs from a recognized repair facility.
  • fulfills all other waiver requirements.

Waivers are handled on a case-by-case basis and may or may not be granted. A waiver is a last resort. The vehicle must be inspected by a SLCoHD vehicle emissions technician to review all test data and repair information, and to verify the ineffective repairs. Contact the Air Quality Bureau for more information about waivers.


USE ONLY THE FREE ADOBE ACROBAT READER TO COMPLETE AND SUBMIT YOUR APPLICATION OR RECERTIFICATION FORM. Some web browser PDF viewers may not properly submit your application or form.


Note that permits are not transferable; when a change of ownership occurs at a permitted facility, the new owner must apply for a new permit and pay all applicable fees.

Emissions Stations in good standing with SLCoHD may apply to become a Vehicle Repair Assistance Program (VRAP) repair station. For more information, contact the Air Quality Bureau.


Utah Foundations Driving Towards a Cleaner Future Report (November 2019)


Driving Toward a Cleaner Future: Alternative Fuel Vehicles in Utah examines the incentives and disincentives around electric cars, as well as the policy decisions around preparation for a wide proliferation of electric vehicles in the future. It also examines the incentives and requirements around public and private heavy-duty fleet vehicles.

Key Findings of this Report

  • Electric vehicles – or battery electric cars and plug-in hybrids – accounted for less than 2% of the nation’s new vehicle market share in 2018. In Utah, electric’s market share was about 1.6%.
  • Addressing the fears of consumers is a core challenge in alternative fuel vehicle adoption. Less than a quarter of Americans consider purchasing electric cars because of concerns about running out of power, the availability of charging stations and initial vehicle cost.
  • Utah’s relatively small electric vehicle tax credit was not renewed in 2016, yet electric vehicle market share has continued to increase.
  • The top electric-vehicle-adopting states – all in the West – offer significant incentives. However, the 10 states with the highest market share growth in 2018 offer no incentives (though they all had 2017 market share under one percent).
  • There is evidence that the looming threat of expiring tax credits can encourage short-term market uptake of alternative fuel vehicles.
  • Due to state and local investment, as well as the Volkswagen Settlement and private actors, Utah’s electric vehicle charging infrastructure is poised to quickly expand
  • Large fleet vehicles account for one-third to one-half of Utah’s vehicle emissions, even though they account for only 3% of the vehicle miles traveled.
  • Alternative-fuel, heavy-duty fleet vehicles are more expensive than diesel and have large infrastructure costs, but offer large fuel and maintenance savings.
  • To encourage the market’s embrace of alternative fuel vehicles, state and local governments should continue to explore opportunities to encourage private actors to deploy alternative fuel infrastructure for customers, tenants, employees and visitors.
  • Cities and counties have at least two potential roles to play: adopting building codes that are “future-proof” for the growth in alternative fuel vehicles, and retiring older public-service diesel fuel fleets.
  • Utah may get a substantial air quality return on its tax credit investments by continuing to focus incentives on heavy-duty fleet vehicles and renewing them in 2020.
  • To encourage the market’s embrace of alternative fuel vehicles, public and private sector stakeholders should mount public information campaigns to explain the growing availability of alternative fuel infrastructure and address other consumer fears.

You can download a pdf of the report here

See the comprehensive, 2014, air quality report here.

14th Annual Governor’s Idle Free Declaration


September 1st, 2021

Fourteenth Annual Governor’s Idle Free Declaration


September marks the 14th Annual Governor Declaration for Idle Free in Utah September 2021 and the 2021-2022 Winter Season in Utah. The Governor’s Declaration is currently signed by 76 Utah Mayors who represent more than ¾ of the state’s population. The highly anticipated event will be held on Wednesday, September 1st at 11 AM via a virtual announcement.  Key leaders and advocates for the Idle Free will share their stories, work and support of this unique Utah campaign for clean air and zero emissions. 

Over the past fourteen years, the Idle Free Education programs continue to grow and are supported by Utah Clean Cities, UCAIR, Breathe Utah, Utah Society for Environmental Education and the State Health Department’s Asthma Program and Recess Guide.  To date, these grass-roots programs have directly reached more than 15,000 students, and are growing, across 425 schools. 


We once again initiate the beloved Idle Free Campaign, “Turn Your Key, Be Idle Free” and announce Utah’s official Idle Free Season 2021-2022. After a tumultuous summer of extreme heat and poor air quality due to wildfires, emissions, and other climate disruptions, it is especially important to commit to right action. We each must ask ourselves, as an individual, as a member of your community and a citizen of the state of Utah what you can do? It is simple. Turn Your Key Be Idle Free. It is a ten-second commitment, and everyone can do it. If we can commit to making small changes, these can lead to bigger results. ” Tammie Bostick, Executive Director, Utah Clean Cities


The Turn your Key, Be Idle Free program recognizes the Utah cities that are officially Idle Free cities. To date, the cities of Park City, Salt Lake City, Alta, Holladay, Logan, Cottonwood Heights, Murray, Springdale, Sandy and Draper City all have Idle Free City Ordinances. Zion National Park is also Idle Free.

The summer of 2021 has brought soaring temperatures, limited precipitation, and terrible air quality due to the all too common and seemingly expected wildfire season throughout the west.  These wildfires create extremely unhealthy conditions due to high ozone, soaring PM 2.5 levels and heavy smoke. The smoke this year filled our skies almost the entire summer season.

Combine this smoke with emissions from cars and trucks that consistently contribute to the largest sources of harmful pollutants along the Wasatch Front, the resulting emissions combined with fires have left at-risk groups, and even some of the healthiest individuals, in a  health crisis. Cleaner air can be supported by individuals and organizations who make conscious decisions to limit their emissions. Local government entities, businesses, fleets and many Utah communities are raising the bar for partnership with this annual reminder to stop unnecessary idling. 


“Healthy communities breathe clean air,” said Mikelle Moore, Intermountain Healthcare’s senior vice president and chief community health officer. “We are committed to reducing air pollution outside our facilities and in our communities. We’re grateful for our partnership with Utah Clean Cities in launching idle-free zones on our campuses.


Air quality is a complex issue. There is no “magic bullet” solution to solving our air pollution challenges. Vehicle exhaust makes up about half of the air pollution in Utah, and unnecessary idling contributes a significant amount of emissions into our air shed each day.  Over 80 Utah fleets make a commitment each year with Utah Clean Cities and the communities they serve to run their fleets Idle Free. Since 2013,  Utah Clean Cities annually submits  those idle free reduction reports from Utah’s fleets to the National Renewable Energy Lab, NREL.  Based on Utah Clean Cities annual report data from 2013 to 2020, the Turn Your Key Be Idle Free program has reduced more than 12,298 tons of greenhouse gas (GHG) emissions over the past seven years. That is equivalent to  reducing 25 thousand barrels of oil usage in Utah or eliminating over a million gallons of diesel in Utah.


“UCAIR recently conducted a public survey and the results indicate widespread success of the Idle Free campaign,” said Kim Frost, UCAIR Executive Director. “Eight-nine percent of survey respondents reported that they know what to do to clear the air. More specifically, seventy-two percent of the respondents reported being idle free. Additionally, Utahns said that knowing their actions are making a difference, drives their desire to make a change. We are excited to see the impactful role that the Turn Your Key, Be Idle Free campaign plays in improving Utah’s air quality.”’ 


Utah Clean Cities and Intermountain Healthcare have partnered to bring awareness to the impacts idling has on individual and community health through an updated signage campaign.  These updated visual images of the Idle Free signs can be seen throughout Intermountain Healthcare Campuses. Ten new signs will be installed at Utah Valley Hospital during the month of September, with more to be installed throughout the region. It is our collective hope to remind visitors of the importance of turning off our vehicles to support the safety and well-being of employees, patients, and visitors. 



September 2021

September 2021