Light-Duty

For nearly two decades, diesel particulate filters have been used to control particle mass and particle number for diesel passenger cars. In recent years, Europe (with Euro 6 emission standards) and China (with China 6 emission standards) have taken bold steps in emissions regulations for light-duty vehicles, tackling particulate emissions from fuel efficient gasoline-direct-injection (GDI) vehicles. Not only have limits have been placed on the particle mass emitted from vehicles, but the latest regulatory additions also regulate the number of soot particles allowed in vehicle exhaust to reduce the emission of ultra-fine particulates (larger than 23 nanometers in size).

To reach the defined limits of ultra-fine particulates, automakers have added gasoline particulate filters (GPFs) to their emissions control systems in China and Europe. These highly efficient exhaust filters trap most of a vehicle’s particulate emissions, including ultrafine particles, preventing them from leaving tailpipes or eventually entering the atmosphere.

In addition, Europe also instituted real-world driving emissions norms, known as real-world driving emissions (RDE). To put it simply, RDE is a regulatory compliance protocol that ensures vehicles meet emissions limits not only under controlled conditions but also during every day on-road driving. This includes a wide range of different driving conditions such as driving uphill, rapid accelerations, driving on motorways as well as in cities, and in different outdoor temperatures including cold weather. Portable emissions measurement systems (PEMS) are used to monitor the tailpipe in real-time, making sure that vehicles stay within emissions limits.

Latest EU6d regulations have already resulted in a significant reductions in the emissions of gaseous pollutants when compared with vehicles developed to meet prior regulations. However, a further tightening is expected for the next regulation stage: EU7.

Future regulations in Europe (EU7) and China (CN7), which are expected to be implemented before 2030, are likely to significantly tighten gaseous and particulate emissions, requiring advanced emissions-control technologies.

Heavy-Duty

For heavy-duty vehicles, a proposal is also being drafted for EU VII standards. As in light-duty, reducing NOx and particulate emissions limits, including particles down to 23 nm are in discussion. Additionally, the introduction of a limit on nitrous oxide (N₂O) and methane (CH₄) is being discussed. Overall, compliance is being strengthened to include all normal driving conditions as well as cold start emissions. New advanced technologies will also be needed to meet these regulations as well.    

In the United States, emission standards are regulated by the EPA (United States Environmental Protection Agency) and by CARB (California Air Resources Board). 

Light-Duty

Tier 3 standards are still being phased in for light-duty vehicles (2017-2025). The EPA provides a summary of the standards here.

Though the US Clean Air Act of 1970 and its amendments have long served as a model for emissions regulations around the world, the US has chosen to use only a particle mass regulation instead of both a mass-based and a particle number-based regulation. As a result, particulate filters are not being used on US gasoline cars as they are in Europe and China. It is anticipated that the upcoming US Tier 4 regulations will require GPFs.

Heavy-Duty

California has proposed significant reductions in NOx and particulates from internal combustion engines while extending the full useful life requirements. They are also forcing a subset of their overall fleet to zero emissions vehicles. The US EPA Cleaner Trucks Plan is also proposing significant NOx reductions, likely requiring advanced technologies.

Learn more about the U.S. Clean Air Act and its success in cleaning up ambient air nationwide

In 2018, Delhi was ranked the most polluted capital in the world and, in total, 22 out of 30 most polluted cities were to be found in India. As a result, the Indian government has been taking strong regulatory action to limit tailpipe emissions. In April 2020, India skipped a regulatory phase and moved from Bharat Stage (BS) 4 in light-duty and BS IV in heavy-duty, to BS 6/VI norms, which closely reflect European vehicle emissions regulations.