3 Things to Know About Hamilton County Emissions Tests

Hamilton County car owners are familiar with the annual ritual. You pull up to an emissions testing facility, pay $9, and cross your fingers the car passes without additional maintenance fees.

Emissions testing seems tedious on the surface, but it, along with other pollution reduction programs, improve environmental and human health. This is especially true in metropolitan areas where a high number of vehicles pollute the air and create smog. Hamilton County began its program after the Environmental Protection Agency (EPA) found it did not meet the attainment standards of the Clean Air Act in 2004. Five other Tennessee counties—Davidson, Rutherford, Sumner, Williamson, and Wilson—have similar programs.

A new bill being debated in the Tennessee Legislature would ban these counties from operating or renewing a vehicle inspection and maintenance program. These counties are currently in “attainment status” under federal law, according to the Tennessee Department of Environment and Conservation (TDEC).

In light of proposed legislation, it is important to understand some key aspects of emissions testing in order to better understand this practice in Tennessee and the potential effects of its removal. Here are three things you should know about emissions testing.

1. Emissions tests have contributed to cleaner air in large cities.

After World War II, an industrial boom and rising dependence on personal vehicles significantly increased air pollution and impacted health and the environment. Congress passed the Clean Air Act in 1970, giving the EPA authority, among other powers, to regulate pollution coming from mobile sources like automobiles. In 1983, cities with heavy air pollution established vehicle inspection programs, which required periodic testing.

While it is difficult to isolate emissions testing from other air pollution controls, it has played a large role in reducing air pollution, especially in cities. The EPA has found that reducing emissions from transportation has significantly bettered air quality and health through the reduction of smog and soot.

Emissions programs lead to innovative technologies and cleaner cars. Cars have 98 percent cleaner tailpipe emissions now than they did in the 1960s. Data shows that by 2030, vehicle emissions standards are projected to annually prevent 40,000 premature deaths, 34,000 hospitalizations, and 4.8 million workdays lost.

2. Emissions testing may be becoming less effective.

Emissions testing has helped cities, but it is harder to demonstrate their effectiveness in rural areas, which have fewer cars on the road.

A 2017 study tested for a link between mandated emissions inspections and air pollution levels. Researchers found that the reinspection of older cars reduced several types of major air pollutants. However, they also found that reinspection of newer vehicles in their test site did not significantly affect air pollution. Further, they found that emissions testing stations need to be of good quality in order to effectively reduce pollution, as bad quality-testing stations do not effectively monitor or reduce pollution.

The study concludes that emissions testing, particularly for older cars, has a positive effect on the environment. As older cars are phased out, we may be approaching a time where testing costs outweigh the smaller gains in pollution reduction.

However, some states are balancing the cost of testing.

According to the Illinois EPA, emissions from car and truck exhaust is one of the greatest sources of air pollution in the Chicago area. The state has found ways to maintain its program and account for newer, cleaner cars. Cars built after 1996 are tested every other year once they are four years old. Testing cars based on their ages opens the door to alternative solutions for cities and metro areas where emissions testing is still helpful and would cost less due to decreased frequency.

3. Eliminating emissions testing poses economic losses and gains.

According to the EPA, there are several economic benefits to emissions testing:

The vehicle emissions control industry employs approximately 65,000 Americans with domestic annual sales of $26 billion. …

For every one dollar spent on programs to reduce emissions, the American people receive nine dollars of benefits to public health, productivity, consumer savings, and the environment.

The Tennessee legislation banning emissions testing would affect state and local revenue, according to the bill’s fiscal note. Recurring state revenue would decrease by $1,668,987 in fiscal year 2019–20. It would decrease $3,008,115 by FY 2022–23 and subsequent years.

Table 1: Tennessee vehicle inspection revenue distributed to county clerks
County Fee revenues
Hamilton $286,429
Rutherford $232,078
Sumner $126,216
Williamson $200,782
Wilson $81,710

The fiscal note also warns that, without an implementation plan, Tennessee could face sanctions and withholding of federal funding. The state received $1,454,883 under the Clean Air Act this fiscal year.

Despite these decreases, consumers might benefit from eliminating the program. They would not have to pay maintenance costs or testing fees. The bill’s proponents suggest that eliminating emissions testing would benefit drivers in low-income communities, who tend to drive older cars and face a disproportionate cost burden.

Many environmental advocates and researchers counter that low-income communities, who face disproportionate health and environmental impacts of pollution, will suffer and pay more in the long run with lower clean air standards. However, other researchers argue that since it is hard to directly measure or link emissions testing to direct air pollution reduction, it may be too costly compared to the environmental benefit.


Emissions testing faces logistical hurdles before it can be phased out. Tennessee would have to negotiate with the EPA to ensure the state is meeting federal pollution standards and has a plan to ensure compliance with the Clean Air Act. If the EPA does not approve changes to the implementation plan, Tennessee could be subject to sanctions. Additionally, many of the counties with emissions testing have contracts with TDEC until 2019.

Regardless of the decision, the primary takeaway is that environmental accountability and pollution regulation are still incredibly crucial at the state and federal levels. If the Legislature bans testing, the state needs to ensure it does not open the door to more relaxed air pollution standards, while maintaining its attainment status.

Air pollution is linked to serious health conditions like cardiovascular and lung disease, and hinders early childhood development. These risks are compounded for communities of color and low incomes. Without accountability measures in place, manufacturing and industry may engage in a hazardous relaxation of standards to cut costs.

Despite Volkswagen cheating to get around emissions tests, these standards have reduced air pollution and pushed innovations in cleaner car technology. Emissions testing may be becoming less effective, but the trajectory for cleaner and greener car manufacturing needs to be a priority for companies and governments. Accountability and environmental standards are still necessary to ensure the health and safety for our communities and environment.

Alea Tveit

Research assistant