Car Emissions Guide

Your Complete Guide to Car Emissions

How Your Vehicle Impacts the Environment

According to the Environmental Protection Agency, emissions are a byproduct of a moving motor vehicle. In order for a car to have power to run, it must be fueled by gasoline. Within the combustion process of a moving motor vehicle, pollution is formed through exhaust.

Emissions are created when fuel used to power a car evaporates into the environment.
• Evaporative Emissions
• Refueling Losses
Exhaust Emissions

Several pollutants in vehicle exhaust can cause widespread problems:


Toxic and may be responsible for some cancer

Released through

Diurnal evaporative emissions, as well as running losses, hot soak, and refueling.

Nitrogen Oxides

Cause the formation of acid rain

Carbon Monoxide

Reduces oxygen flow in the bloodstream and may be dangerous to those at risk for heart disease

Carbon Dioxide

Considered a greenhouse gas that contributes to global warming

“Evaporative losses can account for a majority of the total hydrocarbon pollution from current model cars on hot days when ozone levels are highest.”

– EPA (United States Environmental Protection Agency)

The government started to take notice of vehicle exhaust as far back as the Clean Air Act of 1970.

This legislation provided the EPA with the golden opportunity to regulate vehicle pollution. Since its enactment, EPA emission control policies have grown stricter in an attempt to protect public health and the environment. Nowadays, Environmental Protection Agency standards regulate the amount of pollution cars can emit, though it is up to the automaker to determine how to manufacture vehicles within these set limits.

Both the environment and public health are major concerns in the regulation of emissions.

Based on research from the University of California, Los Angeles School of Public Health, in review of children listed in the California Cancer Registry from 1998 to 2007, traffic pollution was linked with up to a 15% increase in some cancers. Much of this was associated with exposure during pregnancy and the first year of a child’s life.

Most of us are concerned with how vehicle emissions negatively impact the environment, especially related to global warming—and rightly so.

According to the Union of Concerned Scientists, transportation is responsible for almost 30% of the global warming emissions in the US. The process of global warming causes climate disruption. These climate disruptions risk our food and water supply and also endanger public health. Examples include melting glaciers, record high temperatures, and unprecedented droughts and flooding.


of transportation emissions in America are produced by cars and light trucks.


3% Misc

2% Military

18% Freight trucks & buses

2% Rail

10% Aircraft

4% Ships

To put it in perspective,

Every gallon of gas your car burns emits 24 pounds of carbon dioxide, as well as other global-warming gases that release directly into the atmosphere.
The majority of emissions that trap heat and contribute to global warming, estimated at 19 pounds per gallon, come directly through the tailpipe of a car. When you think about how many drivers are on the road at any given moment and how often you have driven in your life, it’s plain to see that vehicle emissions are a serious cause for concern.

What Is a Vehicle Emissions Test?

Clearly, motor vehicle emissions must be regulated.

As the Environmental Protection Agency has worked to regulate vehicle emissions and protect our environment within the past 40 years, vehicle emissions tests have been introduced, updated, and further legislated to allow a car to drive legally.

Nonetheless, an official emissions test is needed to allow environmentally sound vehicles on the road.

While motor vehicle manufacturers have done their part to improve manufacturing methods to meet stringent pollution control standards, older vehicles or vehicles that are not well-maintained can easily fall below par.

In most cases, vehicle emission control should be a non-issue. Modern vehicle design has improved engine efficiency. Innovative engine design coupled with features like electronic ignition, precise ignition timing and fuel metering, and computerized engine management naturally reduce a car’s burden on the environment via exhaust and emissions.

If a large number of vehicles don’t meet clean air requirements on the road, both public health and the environment are immediately affected. A vehicle emissions test will identify cars in need of repair to reduce emissions and meet pollution control standards.


of vehicles fail their emission inspection the first time.

The simple act of testing as a requirement to drive legally has greatly improved environmental outlook. Identifying vehicles in need of maintenance has cut down ozone precursor emissions by more than 4000 pounds per summer day; vehicle repairs required by emissions testing provide an added benefit to the owner to improve both performance and fuel economy.

The type of emissions test needed for your vehicle may vary by:

Age of vehicle

In some counties in Texas, 1995 and older vehicles are required to pass the Two Speed Idle (TSI) test; 1996 and newer vehicles are required to pass the On-Board Diagnostic (OBDII) test. In other Texas counties, older vehicles may be required to pass the Accelerated Simulation Mode (ASM) test. In some states, vehicle emissions tests cost as little as $15 with a free retest available.

catching “gross polluters”

Smog sensors are being setup on freeway on ramps in California to analyze exhaust emissions from passing cars. A camera will take a photo of the car’s license plate and owners of cars that emit large amounts of polution will receive a letter in the mail asking them if they want to participate in a voluntary repair program.

If you don’t want to waste your time and money, it is possible to prepare your vehicle for a successful emissions test with these EPA guidelines:

Test your vehicle as soon as possible, even if a check engine light is on. This will help to diagnose problems early on.

Try not to test during peak times—on Saturdays or at the end of the month.

Make sure your vehicle is safe to operate before the test, or it may be rejected.

Leave the engine running upon arrival at the testing station, unless stated otherwise.

If your car fails the emissions test

You will not be allowed to drive legally until it is repaired and able to pass.

You can be ticketed for driving without valid registration.

Your car must pass its emissions test before you can renew registration.

You may also be charged a late fee if your vehicle has passed its scheduled emissions test date.

How Car Emissions Impact the Environment

The environment is the most concerning factor in the regulation of car emissions. Every day, with every car that is driven, vehicle pollution is released to burden public health and the environment. When vehicle emission regulation began back in 1970, vehicle miles traveled (VMT) was estimated at 89.9 billion by the US Department of Transportation. That number more than tripled to 246.3 trillion VMT in 2011.

In translation

There has been a marked increase in road traffic in the past 40 years. You can only imagine that this also greatly increases the amount of car pollution that affects the environment and ozone layer. A car engine regularly releases a number of gases and particles into the environment, as mentioned above; these include volatile organic compounds (as well as carcinogens), sulfur oxides, nitrogen oxides, particulate matter, and solid particles like soot and metal.

the Clean Air Act of 1970
Fortunately, the Clean Air Act of 1970 has served its purpose to actually improve air quality in the new millennium. Because of this legislation, lead emissions from vehicles have been almost entirely eliminated after leaded gasoline was phased out.
Vehicle emissions impact the environment in a number of ways:

Compromise air-quality

Release greenhouse gases

Deplete ozone layer

Decrease water quality

Expend valuable natural resources

non-renewable resources

The manufacturing, operation, and maintenance of vehicles alone have an environmental impact. This process utilizes valuable non-renewable resources, including metals, petroleum, and other fossil fuels. These resources in our environment are limited and should be used sparingly. Vehicle use and emissions also affect water quality as byproducts like oil and particles are washed into our nation’s water supply. This process utilizes valuable non-renewable resources, including metals, petroleum, and other fossil fuels. These resources in our environment are limited and should be used sparingly. Vehicle use and emissions also affect water quality as byproducts like oil and particles are washed into our nation’s water supply.

ozone layer

Vehicle emissions affect the precious ozone layer. The ozone layer is found in the upper atmosphere and protects life on earth by shielding the planet from UV radiation produced by the sun. When the ozone layer is compromised, the effects of UV radiation are more apparent—including genetic damage, immune system deficiency, skin cancer, and decreased agricultural productivity.

greenhouse gases

We’ve already confirmed that vehicle emissions produce greenhouse gases that support climate change and global warming. The main offending greenhouse gas is carbon dioxide, followed by methane and nitrous oxide. As greenhouse gases increase in the atmosphere, they trap heat released from the surface of the earth. Excess greenhouse gases released by vehicle emissions increase the temperature of the earth and affect global climates, including rainfall and temperature.

air pollution

Last but not least, vehicle emissions directly affect air quality with more cars traveling longer distances. Fortunately, as vehicle regulation has increased with more stringent emission standards, motor vehicle emissions are decreasing. Air pollution from older, unmaintained vehicles can cause dire health consequences, including allergic and respiratory disorders, lung conditions, and increased risk of cancer.

5 Alternatives to Vehicle Pollution

Raising awareness is the first and most important step to protect the environment and preserve our natural resources.

The good news is

if you are reading this article, you’re in the right place

You can learn how to reduce your carbon footprint and drive smart by considering alternatives to vehicle pollution:

Trade in your clunker for a fuel-efficient car

If you’ve been meaning to buy a new car for some time, you can take advice from the EPA. The Environmental Protection Agency recommends shopping for the “cleanest, most fuel-efficient vehicle that meets your needs” when buying new, used, or renting a car. Green vehicle alternatives abound and may include flexible fuel vehicles (FFVs powered with 85% ethanol and 15% gasoline), electric vehicles (EVs), plug-in hybrid electric vehicles (PHEVs), compressed natural gas vehicles (CNG), and fuel cell vehicles powered with pressurized hydrogen (FCVs).

Ride a bicycle whenever possible

Not only is riding a bike good for your health, but it can reduce your carbon emissions to zero. Some employers may reward this environmentally-friendly commute option with up to a $20 reimbursement per month per employee, according to the Bicycle Commuter Act.

Take the bus to work

If you live in an urban area, taking the bus may be your best bet in lieu of driving your vehicle. Not only will you save time and money on parking, but you may even get to work faster as buses can drive in reserved lanes and bus rapid transit systems (BRT).

Take the train/rail

Commuters are encouraged to take public transit like a train or underground, high-speed, or light rail whenever possible. A rail ticket may cost more than a bus ticket, but rail use cuts down significantly on roadway traffic. In addition to the environmental benefit, there are a number of added benefits for the commuter—like decreased travel time, improved health by reducing daily driving stress, and more personal time provided by an efficient commute.

Carpool with friends or coworkers

At the very least, consider joining forces with friends or coworkers in your area to share a ride to work, school, or another destination. Carpooling can help reduce commuter costs and vehicle roadway use. Carpoolers are eligible for High Occupancy Vehicle (HOV) lanes to decrease transit time and toll costs. Carpooling will reduce excess emissions released each day and can also decrease wear and tear on your personal vehicle.

Paying attention to your vehicle emissions can reduce your carbon footprint.

By making simple changes to your driving preferences and habits, you can clean up our air and water supply and preserve natural resources. Even carpooling just once a week can reduce your travel carbon footprint by 20%.

Every choice makes a difference

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