EU: Heavy-duty: Emissions


Euro VI standards have applied to all new diesel and gas engines since 2013. Testing is performed on engines alone rather than on complete vehicles, and limit values are expressed in terms of grams per kilowatt-hour (g/kWh).

Standard type
Conventional pollutant emission limits
Regulating Body
European Union (European Commission, Parliament, Council, and Member States)
Current Standard
Euro VI
Motor vehicles of categories M1, M2, N1, and N2 with a reference mass exceeding 2 610 kg and to all motor vehicles of categories M3 and N3


Europe first introduced heavy-duty vehicle emission standards in 1988. The “Euro” track was established beginning in 1992 with increasingly stringent standards implemented every few years. The heavy-duty Euro standards are numbered using Roman numerals (e.g. Euro I, II….V), whereas light-duty standards use Arabic numbers (e.g. Euro 1, 2…5). Testing is performed on engines alone rather than on complete vehicles, and limit values are expressed in terms of grams per kilowatt-hour (g/kWh) rather than grams per kilometer traveled (g/km).

Many countries have since developed regulations that are aligned in large part with the European standards; the following are some of the most important rulemaking steps in the heavy-duty engine regulations:

Euro I and II

Euro I standards were introduced in 1992, followed by the introduction of Euro II regulations in 1996. These standards applied to both truck engines and urban buses; the urban bus standards, however, were voluntary.

Euro III, IV, and V

The EU adopted Directive 1999/96/EC in 1999, which introduced Euro III standards (2000), as well as the Euro IV/V standards (2005/2008). The directive set voluntary emission limits that are slightly more stringent than Euro V standards for “enhanced environmentally friendly vehicles” or EEVs.

The following directives were important additions or amendments to the original standards:

  • Defeat Devices – In 2001, the European Commission adopted Directive 2001/27/EC which prohibits the use of emission “defeat devices” and “irrational” emission control strategies, which would reduce the efficiency of emission control systems when vehicles operate under normal driving conditions to levels below those determined during the emission testing procedure.
  • Amended Euro IV and VDirective 2005/55/EC adopted by the EU Parliament in 2005 introduced durability and on-board diagnostics (OBD) requirements, as well as re-stated the emission limits for Euro IV and Euro V which were originally published in 1999/96/EC. In a “split-level” regulatory approach, the technical requirements pertaining to durability and OBD—including provisions for emission systems that use consumable reagents—have been described by the Commission in Directive 2005/78/EC.

When Euro IV and Euro V standards were adopted, regulators expected the stringent PM emission standards to require the use of DPFs (Diesel Particulate Filters) in commercial heavy-duty vehicles. However, by tuning their engines for high-NOx, high-fuel economy and relatively low PM emissions, manufacturers are able to comply with the Euro IV and V emission standards without the use of DPFs. These manufacturers use selective catalytic reduction to lower tailpipe NOx emissions to meet Euro IV and Euro V standards. However, this compliance strategy does not reduce emissions of the smallest and most hazardous particles to the same degree as DPFs.

Euro VI

Euro VI emission standards were introduced by Regulation No 595/2009, which was published on 18 July 2009 (with a Corrigenda of 31 July 2009). The new emission limits, comparable in stringency to the US 2010 standards, became effective in 2013 for new type approvals and for all registrations in 2014.

Additional provisions of the Euro VI regulation include:

  • An ammonia (NH3) concentration limit of 10 ppm applied to diesel (WHSC + WHTC) and gas (WHTC) engines.
  • A maximum limit for the NO2 component of NOx emissions may be defined in the implementing regulation.
  • New testing requirements for off-cycle emissions (OCE) and in-service conformity (in-use testing).

EU Member States are allowed to use tax incentives in order to stimulate marketing and sales of vehicles meeting new standards ahead of the regulatory deadlines. However, the use of incentives is contingent upon the following:

  • They apply to all new vehicles offered for sale on the market of EU Member States that comply in advance with the mandatory limit values set out by the directive.
  • They terminate when the new limit values come into effect.
  • They must not exceed the additional cost of the technical solutions introduced for each type of vehicle. This is to ensure compliance with the limit values.

Technical Standards

Euro I-VI

The following table contains a summary of the emission standards and their implementation dates. Dates in the tables refer to new engine type approvals; the dates for all vehicle sales and registrations are in most cases one year later (unlike the US program where engine models must be certified every year, EU type approvals only occur once per emission level e.g. Euro V). As part of the Euro VI regulation, particle number (PN) limits were added, to be met in addition to the PM mass based limits.

EU Emission Standards for HD Diesel Engines, g/kWh (smoke in m-1)
Tier Date Test CO HC NOx PM Smoke
Euro I 1992 (< 85 kW) R-49 4.5 1.1 8.0 0.612
1992 (> 85 kW) 4.5 1.1 8.0 0.36
Euro II October 1996 4.0 1.1 7.0 0.25
October 1998 4.0 1.1 7.0 0.15
Euro III Voluntary EEV (October 1999 to January 2013) ESC & ELR 1.5 0.25 2.0 0.02 0.15
October 2000 ESC & ELR 2.1 0.66 5.0 0.10
Euro IV October 2005 1.5 0.46 3.5 0.02 0.5
Euro V October 2008 1.5 0.46 2.0 0.02 0.5
Euro VI January 2013 WHSC 1.5 0.13 0.4 0.01
Notes:a – for engines of less than 0.75 dm3 swept volume per cylinder and a rated power speed of more than 3000 min-1

EEV – enhanced environmentally-friendly vehicles

Emission standards for diesel engines that are tested on a transient test cycle, as well as for heavy-duty gas engines, are summarized below.

Emission Standards for Diesel and Gas Engines, Transient Test, g/kWh
Tier Date Test CO NMHC CH4a NOx PMb
Euro III Voluntary EEV (October 1999 to January 2013) ETC 3.0 0.40 0.65 2.0 0.02
October 2000 ETC 5.45 0.78 1.6 5.0 0.16
Euro IV October 2005 4.0 0.55 1.1 3.5 0.03
Euro V October 2008 4.0 0.55 1.1 2.0 0.03
Euro VI January 2013 WHTC 4.0 0.16d 0.5 0.46 0.01
Notes:a – for gas engines only (Euro III-V: NG only; Euro VI: NG + LPG)
b – not applicable for gas fueled engines at the Euro III-IV stages
c – for engines with swept volume per cylinder < 0.75 dm3 and rated power speed > 3000 min-1d – THC for diesel engines

Particle Number Limits

At the Euro VI stage, the following PN limits are applicable to diesel engines:

  • 8.0×1011 per kilowatt-hour over the WHSC test
  • 6.0×1011 per kilowatt-hour over the WHTC test

A PN limit for gas engines is to be defined at a later time.


The steady-state engine test, ECE R-49, has been replaced by two cycles since the Euro III stage (2000): the European Stationary Cycle (ESC) and the European Transient Cycle (ETC). Smoke opacity is measured on the European Load Response (ELR) test. Since Euro VI, emissions are tested over the WHSC and WHTC cycles. The following testing requirements apply:

Compression ignition (diesel) engines:

  • Euro III:
    • Conventional diesel engines: ESC/ELR test
    • Diesel engines with “advanced aftertreatment” (NOx aftertreatment or DPFs) and EEVs: ESC/ELR + ETC
  • Euro IV-V: ESC/ELR + ETC
  • Euro VI: WHSC + WHTC

Positive ignition gas (natural gas, LPG) engines:

  • Euro III-V: ETC cycle
  • Euro VI: WHSC + WHTC cycle

Further, detailed information about test cycles used in the EU is available at the EU Test Cycles page.


Effective since October 2005, for new type approvals, and since October 2006, for all engine sales and registrations, manufacturers should demonstrate that engines comply with the emission limit values for useful life periods which depend on the vehicle category, as shown in the following table.

Emission Durability Periods
Vehicle Category† Period*
Euro IV-V Euro VI
N1 and M2 100 000 km / 5 years 160 000 km / 5 years
N3 ≤ 16 ton
M3 Class I, Class II, Class A, and Class B ≤ 7.5 ton
200 000 km / 6 years 300 000 km / 6 years
N3 > 16 ton
M3 Class III, and Class B > 7.5 ton
500 000 km / 7 years 700 000 km / 7 years
† Mass designations (in metric tons) are “maximum technically permissible mass”
* km or year period, whichever is the sooner

Effective October 2005 for new type approvals and October 2006 for all type approvals, type approvals also require confirmation of the correct operation of the emission control devices during the normal life of the vehicle under normal conditions of use (“conformity of in-service vehicles properly maintained and used”).

Fuel Quality

The Euro III and Euro IV standards were preceded by the introduction of more stringent fuel regulations that required a minimum diesel cetane number of 51 (year 2000), maximum diesel sulfur content of 350 ppm in 2000 and 50 ppm in 2005, and maximum petrol (gasoline) sulfur content of 150 ppm in 2000 and 50 ppm in 2005. “Sulfur-free” diesel and gasoline fuels (≤ 10 ppm S) became available in 2005 and became mandatory from 2009.

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