Emission Standards: How Limits Work, US Tier 3 vs Euro 7

An emission standard is a legal limit on how much of a named pollutant a vehicle or engine may emit, measured on a prescribed test over a prescribed period of the vehicle’s life. In the United States the Tier 3 rule sets, for example, a fleet-average limit of 0.030 g/mile for combined non-methane organic gases and nitrogen oxides (NMOG+NOx) on the FTP test. In the European Union, Regulation (EU) 2024/1257 (Euro 7) starts applying to new car and van types on 29 November 2026.

Definition and scope

A standard is not a single number. Reading one correctly means identifying five things: which pollutant is limited, which test cycle and fuel it is measured on, what unit the limit is written in, how long the limit must keep being met, and whether the limit applies to every vehicle or to a manufacturer’s fleet average. The same word, “standard”, is used for the whole package, which is why a quoted figure without its test and useful life is easy to misread.

This page covers road-vehicle exhaust and related standards as defined in two primary instruments: the US Code of Federal Regulations (40 CFR Part 86, light-duty vehicles) and the EU’s Regulation (EU) 2024/1257. For what the regulated pollutants are and how EPA drive schedules work, see the CASRAI guides on vehicle emissions and drive cycles; this page does not repeat that material and concentrates on how limits are structured and when they apply.

How a standard is built

1. Pollutant and unit

The US Tier 3 table in 40 CFR 86.1811-17 expresses limits in grams per mile and groups hydrocarbons as NMOG, combined with NOx into one NMOG+NOx figure. It lists separate limits for particulate matter (PM), carbon monoxide (CO) and formaldehyde. Regulation (EU) 2024/1257 keeps the Euro 6 limits for cars and vans (categories M1 and N1) but changes how particles are counted: the particle-number limit now covers particles above 10 nm.

2. Test cycle and fuel

The Tier 3 limits attach to named tests. The data table below separates the FTP (Federal Test Procedure) values from the SFTP (supplemental FTP) values; PM, for instance, has a different limit on the FTP (0.003 g/mile) and on the US06 supplemental test (0.006 g/mile). Hydrocarbon limits are written as NMOG, and the regulation specifies E10 test fuel. A result reported without its cycle and fuel cannot be compared with a limit.

3. Useful life

Under 40 CFR 86.1805-17, useful life is expressed in years or miles, whichever comes first. For criteria pollutants it is 15 years or 150,000 miles for LDT2, HLDT, MDPV and heavy-duty vehicles, and 10 years or 120,000 miles for LDV and LDT1. Cold-temperature NMHC has its own life periods (10 years/120,000 miles for LDV and LLDT; 11 years/120,000 miles for HLDT and HDV), and cold-temperature CO is set at 5 years or 50,000 miles. So the same pollutant can carry different durability obligations depending on vehicle class.

4. Per-vehicle limit or fleet average

Tier 3 FTP NMOG+NOx is a fleet-average standard of 0.030 g/mile, met by averaging across a manufacturer’s model-year sales using certification bins and a family emission limit (FEL) set for each test group. Credits can be banked and traded (40 CFR 86.1860 and 86.1861). A footnote to the table gives a fleet-average value of 0.026 g/mile for LDV and LDT1 test groups certified to the 120,000-mile, 10-year useful life. The practical consequence is that an individual vehicle may certify above or below the headline figure while the fleet average still meets it.

The data table below lists the fully phased-in Tier 3 exhaust values from 40 CFR 86.1811-17 with the basis for each.

United States: Tier 3 and the 2027-2032 rule

EPA’s Tier 3 final rule is dated April 2014 (with amendments in April 2016). The new standards and the gasoline sulfur standard start in 2017 and cover cars, light trucks, medium-duty passenger vehicles and some heavy-duty vehicles. EPA’s light-duty regulations page also lists a multipollutant rule issued on 20 March 2024 for light- and medium-duty vehicles, with standards phasing in over model years 2027 through 2032. For heavy-duty highway vehicles, the Federal Register notice 89 FR 29440 (22 April 2024), “Greenhouse Gas Emissions Standards for Heavy-Duty Vehicles-Phase 3”, sets greenhouse-gas standards for model year 2032 and later, phasing in from as early as model year 2027 for some categories. It also adds battery and zero-emission-vehicle component warranty requirements and customer-facing battery state-of-health monitors for plug-in hybrid and battery electric vehicles. That description is of the rule as published in April 2024.

EPA’s page also lists a proposed rule, “Revision of Tier 4 Criteria Pollutant Standards, Part 1” (dated May 2026), that would amend the phase-in schedule for light- and medium-duty vehicles. It is a proposal, not a final requirement.

European Union: Euro 6 to Euro 7

Regulation (EU) 2024/1257 (Euro 7) applies in stages. The EUR-Lex summary gives these application dates (read 12 November 2026):

Vehicle categories	New types	All new vehicles
M1 (cars) and N1 (vans)	29 November 2026	29 November 2027
M2, M3, N2, N3, O3, O4	29 May 2028	29 May 2029

Besides the change to particle counting above 10 nm, the regulation gives heavier categories stricter limits, including for nitrous oxide (N2O). It introduces limits for non-exhaust emissions, namely brake particles and tyre abrasion, for all categories, sets minimum traction-battery durability requirements for electric and plug-in hybrid vehicles, and adds conformity-of-production and in-service conformity checks. The summary page does not give numeric brake, tyre or battery values, so none are stated here; the regulation text itself holds them.

“New types” and “all new vehicles” are different obligations. A type approval granted to a model type is the first trigger; a year later (for cars and vans) the rule applies to every new vehicle registered, regardless of when its type was approved.

US and EU compared: structure, not numbers

The two systems cannot be compared by placing one limit beside another, because the instruments are built differently. The table below compares structure only, using the sources above.

Dimension	US Tier 3 (40 CFR Part 86)	EU Euro 7 (Regulation (EU) 2024/1257)
Legal instrument	Code of Federal Regulations, light-duty provisions in 40 CFR 86.1811-17 and 86.1805-17	EU regulation, summarised on EUR-Lex
Unit or counting basis	Grams per mile	Particle-number limit counts particles above 10 nm (Euro 6 limits retained for M1/N1)
Averaging	NMOG+NOx on the FTP is a fleet average, with bins, family emission limits and tradable credits	Conformity-of-production and in-service conformity checks are added
Time basis	Useful life in years or miles, whichever first, set by vehicle class	Minimum traction-battery durability for EV/PHEV
Non-exhaust sources	Not part of the Tier 3 exhaust table	Brake particle and tyre abrasion limits for all categories
Phase-in	Tier 3 from 2017; multipollutant rule model years 2027-2032	29 Nov 2026 to 29 May 2029 depending on category

Related concepts

• Emission limit versus emission standard. In the sources read, the numeric value (such as 0.030 g/mile) is the limit; the standard is the limit together with its test, fuel, useful life and compliance mechanism.
• Type approval and certification. Euro 7 distinguishes new types from all new vehicles; the US fleet-average standard works through certification of test groups.
• Conformity-of-production and in-service conformity. Checks added under Euro 7 to confirm that vehicles in production and in use continue to meet requirements.
• Criteria pollutants and greenhouse gases. The Heavy-Duty Phase 3 rule is a greenhouse-gas standard; the Tier 3 table is a criteria-pollutant standard.

Where it matters for laboratories and test facilities

A test laboratory or dynamometer facility reporting vehicle emissions has to state, with each result, the standard it refers to, the test cycle, the fuel (E10 for the Tier 3 tests) and the unit, because the limits are defined only against those. Laboratories also need to know whether a limit being used for comparison is a fleet average or a per-vehicle value: a single measured vehicle compared with a fleet-average figure does not show compliance or non-compliance. Method documentation for such work is normally held as a standard operating procedure, and quality frameworks such as good laboratory practice describe how that documentation and the resulting records are controlled.

Common misunderstandings

• “The limit is one number.” The Tier 3 table gives different NMOG+NOx and PM values on different tests, and a different fleet-average figure for LDV and LDT1.
• “A vehicle must meet the limit forever.” Durability is set by useful life, in years or miles, whichever comes first, and it differs by vehicle class.
• “Euro 7 starts on one date.” It applies in stages by vehicle category and by new type versus all new vehicles.
• “Euro 7 loosens or replaces the car limits.” For cars and vans the summary states that Euro 6 limits are kept, with a changed particle-number count and new non-exhaust and battery durability requirements.
• “A proposed rule is in force.” The May 2026 Tier 4 revision listed by EPA is a proposal.

Frequently asked questions

What is the difference between an emission standard and an emission limit?

The limit is the numeric value for a pollutant. The standard is that value together with the test, fuel, useful life and compliance method that give it meaning, as in the structure set out above.

Do emission standards apply to older vehicles?

Each standard applies to the vehicles it names, by model year or approval date. The Tier 3 standards start in 2017, and Euro 7 applies first to new types from 29 November 2026 and to all new cars and vans from 29 November 2027. The sources read do not state retroactive effects on older vehicles.

When does Euro 7 start?

For new types of cars and vans it applies from 29 November 2026; for all new cars and vans from 29 November 2027. For categories M2, M3, N2, N3, O3 and O4 the dates are 29 May 2028 and 29 May 2029.

Sources

• 40 CFR 86.1811-17, Legal Information Institute, Cornell Law School: law.cornell.edu/cfr/text/40/86.1811-17 (read 12 November 2026).
• 40 CFR 86.1805-17, Useful life: law.cornell.edu/cfr/text/40/86.1805-17 (read 12 November 2026).
• EUR-Lex summary of Regulation (EU) 2024/1257: Vehicle emissions and battery durability: Euro 7 (read 12 November 2026).
• US EPA, Regulations for smog, soot and other air pollution from passenger vehicles: epa.gov (read 12 November 2026).
• Federal Register, 89 FR 29440 (22 April 2024), Greenhouse Gas Emissions Standards for Heavy-Duty Vehicles-Phase 3, document 2024-06809: federalregister.gov (read 12 November 2026).