A complete guide to understanding emissions regulations in 2020 and beyond
May 27, 2020
The heavy-duty manufacturing industry's collective effort to mitigate negative impacts on the environment from engine use is nearly two decades old. With varying regulations from country to country and application to application, it can get a bit overwhelming to digest.
Here's a complete guide of current emissions regulations and what those designing the next wave of world-changing machines can expect.
Ever since CO2 emissions became a hot-button issue in the early 1990s, federal and state governments have worked with engine and equipment manufacturers to limit the amount of harmful material entering the atmosphere. Europe first adopted its stages of emissions requirements in 1992; the United States' efforts go all the way back to the Clean Air Act of 1970.
Jump to:
United States on-highway emissions standards
- Phase 2 regulations for heavy-duty trucks
- Phase 2 regulations for engines installed in heavy-duty trucks
- Phase 2 standards for vocational trucks
- Phase 2 standards for engines installed in vocational trucks
European Union on-highway emissions standards
United States off-highway regulations
- Tier 4 emissions standards for engines up to 560 kW
- Tier 4 emissions standards for engines above 560 kW
European Union Stage V emissions limits
Much of the current regulatory landscape can be grouped into on- and off-highway categories for both the United States and the European Union.
United States on-highway
A presidential memorandum issued in May 2010 led to the Environmental Protection Agency and National Highway Traffic Safety Administration's August 2011 adoption for greenhouse gas emissions and fuel economy standards for medium- and heavy-duty trucks with model years 2014-18. These "Phase 1" rules were estimated to reduce CO2 emissions by 270 million metric tons and save owners about $50 billion in fuel, according to the EPA.
In 2016, the EPA and NHTSA formalized Phase 2, which impacts vehicles through model year 2027. These more stringent standards are designed to "cut carbon pollution to reduce the impacts of climate change, while bolstering energy security and spurring manufacturing innovation," the EPA says.
Specifically, they're projected to:
- Reduce CO2 emissions by approximately 1.1 billion metric tons
- Save owners about $170 billion in fuel costs
- Lessen oil consumption by up to two billion barrels over the lifetime of the vehicles sold under the program
The complete regulations comprise hundreds of pages but are summarized in the following tables, adopted from dieselnet.com's regulations overview .
Phase 2 regulations for heavy-duty trucks
| Category | EPA CO2 Emissions (g/ton-mile) | NHTSA Fuel Consumption (gal/1,000 ton-mile) | ||||
| Low Roof | Mid Roof | High Roof | Low Roof | Mid Roof | High Roof | |
| Day Cab Class 7 | 96.2 | 103.4 | 100 | 9.4499 | 10.15717 | 9.82318 |
| Day Cab Class 8 | 73.4 | 78 | 75.7 | 7.21022 | 7.66208 | 7.43615 |
| Sleeper Cab Class 8 | 64.1 | 69.6 | 64.3 | 6.29666 | 6.83694 | 6.31631 |
| Heavy-haul Class 8 | 48.3 | 4.7446 | ||||
Phase 2 regulations for engines installed in heavy-duty trucks
| Category | Year | CO2 Emissions (g/bhp-hr) | Fuel Consumption* (gallon/100 bhp-hr) |
| MHD Engines | 2014 | 502 | 4.93** |
| 2017 | 487 | 4.78 | |
| 2021 | 473 | 4.6464 | |
| 2024 | 461 | 4.5285 | |
| 2027 | 457 | 4.4892 | |
| HHD Engines | 2014 | 475 | 4.67** |
| 2017 | 460 | 4.52 | |
| 2021 | 447 | 4.391 | |
| 2024 | 436 | 4.2829 | |
| 2027 | 432 | 4.2436 |
* Equivalent NHTSA standards based on 10,180 g CO2 per gallon of diesel
** Voluntary in MY 2014 and MY 2015.
Phase 2 standards for vocational trucks
| Category | EPA CO2 Emissions (g/ton-mile) | NHTSA Fuel Consumption (gal/1,000 ton-mile | ||||
| Urban | Multi-purpose | Regional | Urban | Multi-purpose | Regional | |
| Vehicles with CI engines | ||||||
| Light Heavy Class 2b-5 | 367 | 330 | 291 | 36.0511 | 32.4165 | 28.5855 |
| Medium Heavy Class 6-7 | 258 | 235 | 218 | 25.3438 | 23.0845 | 21.4145 |
| Heavy Heavy Class 8 | 269 | 230 | 189 | 26.4244 | 22.5933 | 18.5658 |
| Vehicles with SI engines | ||||||
| Light Heavy Class 2b-5 | 413 | 372 | 319 | 46.4724 | 41.8589 | 35.8951 |
| Medium Heavy Class 6-7 | 297 | 268 | 247 | 33.4196 | 30.1564 | 27.7934 |
Phase 2 standards for engines installed in vocational trucks
| Category | Year | CO2 Emissions | Fuel Consumption* |
| g/bhp-hr | gallon/100 bhp-hr | ||
| LHD Engines | 2014 | 600 | 5.89** |
| 2017 | 576 | 5.66 | |
| 2021 | 563 | 5.5305 | |
| 2024 | 555 | 5.4519 | |
| 2027 | 552 | 5.4224 | |
| MHD Engines | 2014 | 600 | 5.89** |
| 2017 | 576 | 5.66 | |
| 2021 | 545 | 5.3536 | |
| 2024 | 538 | 5.2849 | |
| 2027 | 535 | 5.2554 | |
| HHD Engines | 2014 | 567 | 5.57** |
| 2017 | 555 | 5.45 | |
| 2021 | 513 | 5.0393 | |
| 2024 | 506 | 4.9705 | |
| 2027 | 503 | 4.9411 | |
| HD Gasoline Engines | 2016 | 627 | 7.06 |
* Equivalent NHTSA standards based on 10,180 g CO2 per gallon of diesel
** Voluntary in MY 2014 and MY 2015
European Union on-highway
Europe is currently in the sixth stage of its on-road vehicle emissions standards. The latest round was enacted in 2012 and has been fully implemented since 2015.
According to the International Council on Clean Transportation , the G-20 countries account for 90 percent of global vehicle sales, and most of them have adopted Europe's roadmap for reducing emissions.
Here are the EU's latest mandates, commonly referred to as "Euro VI," courtesy of the ICCT:
Euro VI regulations for heavy-duty vehicles
| Pollutant | Steady-state testing | Transient testing |
| CO | 1.5 | 4 |
| HC | 0.13 | 0.16** |
| Ch3* | 0.5 | |
| Nox | 0.4 | 0.46 |
| PM | 0.01 | 0.01 |
| PN (#/km) | 8.0 x 10 | 6.0 x 10 |
| Ammonia (ppm) | 0.01 | 0.01 |
| Fuel Sulfur Limit (ppm) | 10 | 10 |
| Test Cycle | WHSC | WHTC |
* For Euro V for Natural Gas only, for Euro VI, NG and LPG
** Total HC for diesel engines, non-methane HC for others
Euro VI regulations for light-duty vehicles
| Pollutant | Gasoline | Diesel |
| CO | 1.0 | 0.5 |
| HC | 0.1* | |
| HC+NOX | 0.17 | |
| NOX | 0.06 | 0.08 |
| PM | 0.005** | 0.005 |
| PN (#/km) | 6.0x10*** | 6.0x10 |
*and 0.068 g/km for NMHC
** applicable only to DI engines, 0.0045 g/km using the PMP measurement procedure
*** applicable only to DI engines, 6 x 1012 #/km within the first three years of Euro 6 effective dates
United States off-highway
Emissions compliance isn't limited to the U.S.'s streets and highways. Since 2015, the United States has been in Tier 4 of its NOx and particulate matter emissions standards .
All construction, agricultural and industrial equipment manufactured in the U.S. is subject to these regulations, which were aimed at reducing particulate matter and NOx emissions by 90 percent.
Tier 4 emissions standards for engines up to 560 kW
| Engine Power | Year | CO | NMHC | NMHC+NOx | NOx | PM |
| kW < 8 (hp < 11) |
2008 | 8.0 (6.0) | - | 7.5 (5.6) | - | 0.4* (0.3) |
| 8 ≤ kW < 19 (11 ≤ hp < 25) |
2008 | 6.6 (4.9) | - | 7.5 (5.6) | - | 0.4 (0.3) |
| 19 ≤ kW < 37 (25 ≤ hp < 50) |
2008 | 5.5 (4.1) | - | 7.5 (5.6) | - | 0.3 (0.22) |
| 2013 | 5.5 (4.1) | - | 4.7 (3.5) | - | 0.03 (0.022) | |
| 37 ≤ kW < 56 (50 ≤ hp < 75) |
2008 | 5.0 (3.7) | - | 4.7 (3.5) | - | 0.3** (0.22) |
| 2013 | 5.0 (3.7) | - | 4.7 (3.5) | - | 0.03 (0.022) | |
| 56 ≤ kW < 130 (75 ≤ hp < 175) |
2012-2014*** | 5.0 (3.7) | 0.19 (0.14) | - | 0.40 (0.30) | 0.02 (0.015) |
| 130 ≤ kW ≤ 560 (175 ≤ hp ≤ 750) |
2011-2014**** | 3.5 (2.6) | 0.19 (0.14) | - | 0.40 (0.30) | 0.02 (0.015) |
* hand-startable, air-cooled, DI engines may be certified to Tier 2 standards through 2009 and to an optional PM standard of 0.6 g/kWh starting in 2010
** 0.4 g/kWh (Tier 2) if manufacturer complies with the 0.03 g/kWh standard from 2012
*** PM/CO: full compliance from 2012; NOx/HC: Option 1 (if banked Tier 2 credits used)—50% engines must comply in 2012-2013; Option 2 (if no Tier 2 credits claimed)—25% engines must comply in 2012-2014, with full compliance from 2014.12.31
**** PM/CO: full compliance from 2011; NOx/HC: 50% engines must comply in 2011-2013
There are some alternative options listed on Diesel Net's website. The EPA also lists specific regulations for engines above 560 kW.
Tier 4 emissions standards for engines above 560 kW
| Category | CO | NMHC | NOx | PM |
| Generator sets | 3.5 (2.6) | 0.19 (0.14) | 0.67 (0.50) | 0.03 (0.022) |
| All engines except gensets | 3.5 (2.6) | 0.19 (0.14) | 3.5 (2.6) | 0.04 (0.03) |
European Union off-highway
The EU is currently on Stage V of its non-road mobile machinery regulations, with full implementation slated for 2021. The latest changes are focused on setting stricter limits on particulate matter emissions.
European Union Stage V emissions limits
| Category | Ignition Type | Net Power (kW) | Date | CO (g/kWh) | HC | NOx | PM | PN (1/kWh) |
| NRE-v/c-1 | CI | P < 8 | 2019 | 8 | 7.50a,c | 0.40* | - | |
| NRE-v/c-2 | CI | 8 ≤ P < 19 | 2019 | 6.6 | 7.50a,c | 0.4 | - | |
| NRE-v/c-3 | CI | 19 ≤ P < 37 | 2019 | 5 | 4.70a,c | 0.015 | 1×1012 | |
| NRE-v/c-4 | CI | 37 ≤ P < 56 | 2019 | 5 | 4.70a,c | 0.015 | 1×1012 | |
| NRE-v/c-5 | All | 56 ≤ P < 130 | 2020 | 5 | 0.19c | 0.4 | 0.015 | 1×1012 |
| NRE-v/c-6 | All | 130 ≤ P ≤ 560 | 2019 | 3.5 | 0.19c | 0.4 | 0.015 | 1×1012 |
| NRE-v/c-7 | All | P > 560 | 2019 | 3.5 | 0.19** | 3.5 | 0.045 | - |
| NRG-v/c-1 | All | P > 560 | 2019 | 3.5 | 0.19*** | 0.67 | 0.035 | - |
In the United States, the state of California has special permission from the EPA to enact its own emissions standards -- due in part to severe pollution in the Los Angeles area dating back decades. Colorado, Connecticut, Delaware, Maine, Maryland, Massachusetts, New Jersey, New Mexico, New York, Oregon, Pennsylvania, Rhode Island, Vermont, Washington and the District of Columbia have all adopted the California standards , which are stricter than those of the EPA.
Making sense of it all
That's a lot of data and acronyms, but the EU and EPA provide tools engineers can use to ensure compliance for their specific applications, including the U.S.'s Greenhouse Gas Emissions Model (GEM) and EU's Vehicle Energy Consumption Calculation Tool (VECTO) .
Both allow engineers to provide engine inputs and churn out emission level predictions.
So, where do we go from here?
Regulation evolution tends to follow a pattern. For more than two decades, densely-populated Europe has been on the cutting edge of emissions standards. California is usually a few years behind, with the greater United States coming in a couple years after that.
Other manufacturing-rich countries like China and Japan have their own evolving standards. As the economy becomes more global, major manufacturers have pushed for more harmonization; examples include the United Nations' Paris Agreement and EPA and California Air Resources Board's agreement to implement regulations similar to California's current regulations by 2027.
The global COVID-19 pandemic and lockdown measures to mitigate it have caused CO2 emissions to drop by 17 percent between January and April of 2020. Some scientists are predicting a 4.4 to 8 percent decline by the end of the year, which would mark the largest annual decrease since World War II.
But any dip is expected to be temporary as the transportation industry and global economy recover.
What's unclear is how willing corporations will be to continue aggressive global expansion in the wake of a global health crisis caused by the spread of a virus across countries and continents.
As with most things COVID, predictions are about as good at guesses at this point.
In recent months, the EPA has said it will look to further cut pollution via its " Cleaner Trucks Initiative ." President Donald Trump has rolled back some emissions at the automotive level, meanwhile, so it's unclear how the balance between enabling manufacturers and protecting the world in which they manufacture will be struck moving forward.
One means of doing so is electrification, but full-scale implementation is likely well more than a decade away .
What's more urgent today is another type of emission: noise pollution. The EU's Outdoor Noise Directive limits how many decibels can come from off-highway engines, especially construction equipment and agricultural tractors being operated near an urban setting.
North America is expected to adopt similar measures in the coming years.
