It is relatively common knowledge that burning fossil fuels produces CO2, which contributes to the Earth’s progressive warming, A.K.A. climate change. And yet, it was not until the very recent Inflation Reduction Act in 2022 that carbon dioxide emissions were officially recognized as an air pollutant, affirming their ability to be regulated under the Clean Air Act (CAA). Little did anyone expect that the CAA would evolve into comprehensive vehicle emissions testing procedures.
The landscape of pollutant regulation is an ongoing evolution. This point is underlined by the fact that the EPA was only established 54 years ago, in 1970, by the Nixon administration. The impetus behind the establishment of this agency was the excess of fine particulate matter causing widespread death across the United States. The air quality standards established in the original 1970 Clean Air Act (CAA) sought to regulate six pollutants: sulfur dioxide, nitrogen dioxide, carbon monoxide, ozone, lead, and particulate matter. Automobile emissions were only explicitly addressed with the Clean Air Act Amendments of 1977, though much of the air pollution addressed in the original 1970 legislation could be attributed to vehicle emissions.
The Clean Air Act is, in many ways, the root of the modern-day environmental movement. Though its founding focused on air quality, the 2022 Inflation Reduction Act reinforced a 2007 Supreme Court Case assuring that the original Clean Air Act covers all climate-changing pollution, not just air pollutants.
This development is expected to quell legal challenges to the EPA’s attempts to regulate greenhouse gas emissions, amongst claims that they fall outside of the EPA’s original mandate.
Today, the federal government establishes standards for what level of pollutants is considered safe. Mobile sources of emissions are regulated as well as the quality of fuels they are burning. Pollutants are governed in categories based on many factors, including global warming potential (GWP), geography, and lifespan.
Though the federal government sets the standards, it is the states and territories that must lay out State Implementation Plans (SIPs) to enforce and meet federal standards. If the states fail to meet EPA standards, the EPA will step in to regulate pollution.
Similar to the EPA’s relationship with States, the EPA takes on more of an oversight rather than a primary regulatory role in testing vehicle emissions before vehicles go to market. Vehicle manufacturers must prove that that engine is compliant with the CAA and related EPA regulations.
It is the manufacturers that are responsible for reporting emissions information to the EPA. With this said, manufacturers are not required to test every vehicle in their fleet; instead, they are only required to test one representative vehicle for a group of vehicles with similar design and emission characteristics. The EPA reviews these test results and confirms the results of ~20% of submitted vehicles for themselves. The EPA’s comprehensive vehicle emissions test procedure can be found here.
In addition to the assembly-line certification process, which occurs before vehicles go to market, the EPA also has a Vehicle Emissions Surveillance Program to regulate vehicles in use. This process ensures that vehicles maintain their emissions standards beyond the production line. This testing occurs at the National Vehicle and Fuel Emissions Laboratory in Ann Arbor, Michigan.
According to the EPA’s reporting, they test around 150 2-3 year old customer-owned vehicles each year through this program. Keep in mind, 286 million vehicles are operating on U.S. roads as of early 2023, a number that grows each year.
If you ever hear of a vehicle under an emissions recall, this in-use test is likely the source of that recall.
The EPA counters attempts to subvert emissions regulations to the best of their ability. They also encourage transparency by collecting user-reported fuel efficiency ratings to be displayed alongside their own reported MPG estimates, which are available here. Notably, these fuel efficiency rating are what SHiFT uses to estimate donor’s estimated annual emissions on the SHiFT Carbon Certificate.
To better understand the U.S. system of emissions regulations, one can look to other countries’ attempts at regulation. While the U.S.’s regulatory body is the EPA, the European Union is in charge of directing emissions standards for its member states. There are certain key differences in emissions regulations between the EPA and the E.U.. Generally speaking, the U.S. approach is quite top-down whereas E.U. regulators work more in collaboration with its member states to develop the regulations themselves.
Further, the U.S. regulates by setting a minimum standard of fuel efficiency (MPG) that manufacturers must meet, called the Corporate Average Fuel Economy (CAFE) Standards. This is the basis of much of the EPA’s regulation. The E.U. instead monitors average CO2 emissions as their primary fuel efficiency standard in terms of grams of CO2 per kilometer traveled. This key difference means that the EU is actively tracking collective fuel consumption while the U.S. is less focused on this indicator.
Another difference between the EPA and EU standards is the range of pollutants that each of them governs. Historically the EPA has focused on ‘criteria pollutants’, which are those understood to be the most dangerous to human health; in other words, they are interested in particles larger than 100 micrometers. Comparably, EU standards include pollutants like ammonia, VOCs, and methane. This is also a result of the fact that EU carmakers produce more vehicles with diesel technology rather than gasoline. Diesel engines are known to have greater fuel economy but with the tradeoff that they produce higher levels of particulate matter and smog-forming compounds.
Above all else, the largest difference between these two regulatory bodies has to do with differing test procedures.
The EU recently updated its test procedure, replacing a test designed in the 1980s called the New European Driving Cycle that was determined not to be representative of real driving conditions.
The Worldwide Harmonised Light Vehicle Test Procedure (WLTP) was introduced in 2017 and its intent is to better emulate real-life driving conditions by testing each vehicle at four different speed profiles. These four parts each feature numerous stops, starts, accelerating, and braking components. Compared to the former NEDC, the WLTP features a wider range of driving scenarios and longer tests. Rather than producing an average of these values, the WLTP computes the vehicle’s best-case scenario and worst-case scenario in terms of emissions ratings.
One intention in creating the WLTP was to enable vehicle emissions testing and fuel efficiency ratings to be more easily compared across different countries.
Meanwhile, the US Federal Test Procedure (FTP; current version FTP–75) has four distinct segments: cold start, stabilized phase, hot soak, and hot start transient phase. The distance of the test is 11 miles on average.
The EPA reports that they adjust laboratory results indicating fuel economy ratings by about 10%, as they estimate that laboratory testing understates fuel consumption by this amount given the lack of hills, wind, and unfavorable road conditions.
Recent years have seen the EPA add in other test cycles to account for air conditioning, aggressive driving, and highway driving.
All in all, fuel economy testing is scientific, but also hugely political and influenced by historical events (i.e.1970 oil crisis).
In recent years the EPA and the E.U. have had to develop test procedures for energy consumption and range testing for electric vehicles. A side-by-side comparison of these procedures should be performed to gain a clearer picture of which regulatory body holds vehicle emissions to a higher standard.
History indicates that U.S. regulations are typically slightly more stringent than E.U. standards. With this said, differing test procedures muddy the waters in terms of deciding which body regulates vehicle emissions more stringently.
