The European emission standards for new nonroad diesel engines have been structured as gradually more stringent tiers known as Stage I...IV standards. Additionally, emission standards have been adopted for small, gasoline fueled nonroad engines. The regulations are specified by Directive 97/68/EC with numerous later amendments. The main regulatory steps were:
Stage I/II. The first European legislation to regulate emissions from nonroad (off-road) mobile equipment was promulgated on December 16, 1997 . The regulations for nonroad diesels were introduced in two stages: Stage I implemented in 1999 and Stage II implemented from 2001 to 2004, depending on the engine power output.
The equipment covered by the standard included industrial drilling rigs, compressors, construction wheel loaders, bulldozers, nonroad trucks, highway excavators, forklift trucks, road maintenance equipment, snow plows, ground support equipment in airports, aerial lifts and mobile cranes. Agricultural and forestry tractors had the same emission standards but different implementation dates . Engines used in ships, railway locomotives, aircraft, and generating sets were not covered by the Stage I/II standards.
- Small Utility Engines. On December 9, 2002, the European Parliament adopted Directive 2002/88/EC , amending the nonroad Directive 97/68/EC by adding emission standards for small, gasoline fueled utility engines below 19 kW. The Directive also extended the applicability of Stage II standards on constant speed engines. The utility engine emission standards are to a large degree aligned with the US emission standards for small utility engines.
Stage III/IV. Stage III/IV emission standards for nonroad engines were adopted by the European Parliament on 21 April 2004 , and for agricultural and forestry tractors on 21 February 2005 .
Two additional Directives were adopted in 2010: Directive 2010/26/EU  provides further technical details on the testing and approvals of Stage IIIB and Stage IV engines, and Directive 2010/22/EU  amends the earlier legislation applicable to agricultural and forestry tractors.
Stage III standards—which are further divided into Stages IIIA and IIIB—are phased-in from 2006 to 2013, Stage IV enter into force in 2014. The Stage III/IV standards, in addition to the engine categories regulated at Stage I/II, also cover railroad locomotive engines and marine engines used for inland waterway vessels. Stage III/IV legislation applies only to new vehicles and equipment; replacement engines to be used in machinery already in use (except for railcar, locomotive and inland waterway vessel propulsion engines) should comply with the limit values that the engine to be replaced had to meet when originally placed on the market.
Stage V. The European Commission has been working on a new stage of nonroad emission regulations that could potentially include the following components:
- Widening of the scope of regulated engines including CI engines below 19 kW, CI engines above 560 kW, stationary engines, SI engines above 19 kW and snow mobiles.
- Strengthening the emission limits for constant speed engines, inland waterway vessels, and for 19-37 kW engines.
- Adopting particle number (PN) limits for CI engines.
EU nonroad emission standards usually specify two sets of implementation dates:
- Type approval dates, after which all newly type approved models must meet the standard, and
- Market placement (or first registration) dates, after which all new engines placed on the market must meet the standard.
The dates listed in the following tables are the market placement dates. In most cases, new type approval dates are one year before the respective market placement dates.
Regulatory authorities in the EU, USA, and Japan have been under pressure from engine and equipment manufacturers to harmonize worldwide emission standards, in order to streamline engine development and emission type approval/certification for different markets. Stage I/II limits were in part harmonized with US regulations. Stage III/IV requirements are harmonized to a large degree with the US Tier 3/4 standards.
A list of nonroad engine regulations, including the consolidated version of Directive 97/68/EC , can be found in the European Commission web site .
Stage I/II Standards
Stage I and Stage II emissions shall not exceed the amount shown in Table 1. The Stage I emissions are engine-out limits and shall be achieved before any exhaust aftertreatment device.
|A||130 ≤ P ≤ 560||1999.01||5.0||1.3||9.2||0.54|
|B||75 ≤ P < 130||1999.01||5.0||1.3||9.2||0.70|
|C||37 ≤ P < 75||1999.04||6.5||1.3||9.2||0.85|
|E||130 ≤ P ≤ 560||2002.01||3.5||1.0||6.0||0.2|
|F||75 ≤ P < 130||2003.01||5.0||1.0||6.0||0.3|
|G||37 ≤ P < 75||2004.01||5.0||1.3||7.0||0.4|
|D||18 ≤ P < 37||2001.01||5.5||1.5||8.0||0.8|
|* Stage II also applies to constant speed engines effective 2007.01|
A sell-off period of up to two years is allowed for engines produced prior to the respective market placement date. Since the sell-off period—between zero and two years—is determined by each Member State, the exact timeframe of the regulations may be different in different countries.
Emissions are measured on the ISO 8178 C1 8-mode cycle and expressed in g/kWh. Stage I/II engines are tested using fuel of 0.1-0.2% (wt.) sulfur content.
Stage III/IV Standards
Stage III standards—which are further divided into two sub-stages: Stage III A and Stage III B—and Stage IV standards for nonroad diesel engines are listed in Table 2, Table 3, and Table 4, respectively. These limit values apply to all nonroad diesel engines of indicated power range for use in applications other than propulsion of locomotives, railcars and inland waterway vessels.
The implementation dates in the following tables (Table 2 through Table 7) refer to the market placement dates. For all engine categories, a sell-off period of two years is allowed for engines produced prior to the respective market placement date. The dates for new type approvals are, with some exceptions, one year ahead of the respective market placement date.
|H||130 ≤ P ≤ 560||2006.01||3.5||4.0||0.2|
|I||75 ≤ P < 130||2007.01||5.0||4.0||0.3|
|J||37 ≤ P < 75||2008.01||5.0||4.7||0.4|
|K||19 ≤ P < 37||2007.01||5.5||7.5||0.6|
|† dates for constant speed engines are: 2011.01 for categories H, I and K; 2012.01 for category J.|
|L||130 ≤ P ≤ 560||2011.01||3.5||0.19||2.0||0.025|
|M||75 ≤ P < 130||2012.01||5.0||0.19||3.3||0.025|
|N||56 ≤ P < 75||2012.01||5.0||0.19||3.3||0.025|
|P||37 ≤ P < 56||2013.01||5.0||4.7†||0.025|
|Q||130 ≤ P ≤ 560||2014.01||3.5||0.19||0.4||0.025|
|R||56 ≤ P < 130||2014.10||5.0||0.19||0.4||0.025|
Stage III/IV standards also include a limit for ammonia emissions, which must not exceed a mean of 25 ppm over the test cycle.
Stage III B standards introduce PM limit of 0.025 g/kWh, representing about 90% emission reduction relative to Stage II. To meet this limit value, it is anticipated that engines will have to be equipped with particulate filters. Stage IV also introduces a very stringent NOx limit of 0.4 g/kWh, which is expected to require NOx aftertreatment.
To represent emissions during real conditions, a new transient test procedure—the Non-Road Transient Cycle (NRTC)—was developed in cooperation with the US EPA. The NRTC is run twice—with a cold and a hot start. The final emission results are weighted averages of 10% for the cold start and 90% for the hot start run. The new test will be used in parallel with the prior steady-state schedule, ISO 8178 C1, referred to as the Non-Road Steady Cycle (NRSC).
- The NRSC (steady-state) shall be used for stages I, II and III A, as well as for constant speed engines at all stagees. The NRTC (transient) can be used for Stage III A testing by the choice of the manufacturer.
- Both NRSC and NRTC cycles shall be used for Stage III B and IV testing (gaseous and particulate pollutants).
Inland Water Vessels
Unlike the Stage I/II legislation, the Stage III A standards also cover engines used in inland waterway vessels, Table 5. Engines are divided into categories based on the displacement (swept volume) per cylinder and net power output. The engine categories and the standards are harmonized with the US standards for marine engines. There are no Stage III B or Stage IV standards for waterway vessels.
|dm3 per cylinder||g/kWh|
|V1:1||D ≤ 0.9, P > 37 kW||2007.01||5.0||7.5||0.40|
|V1:2||0.9 < D ≤ 1.2||5.0||7.2||0.30|
|V1:3||1.2 < D ≤ 2.5||5.0||7.2||0.20|
|V1:4||2.5 < D ≤ 5||2009.01||5.0||7.2||0.20|
|V2:1||5 < D ≤ 15||5.0||7.8||0.27|
|V2:2||15 < D ≤ 20, P ≤ 3300 kW||5.0||8.7||0.50|
|V2:3||15 < D ≤ 20, P > 3300 kW||5.0||9.8||0.50|
|V2:4||20 < D ≤ 25||5.0||9.8||0.50|
|V2:5||25 < D ≤ 30||5.0||11.0||0.50|
Rail Traction Engines
Stage III A and III B standards have been adopted for engines above 130 kW used for the propulsion of railroad locomotives (categories R, RL, RH) and railcars (RC), Table 6 and Table 7.
|RC A||130 < P||2006.01||3.5||-||4.0||-||0.2|
|RL A||130 ≤ P ≤ 560||2007.01||3.5||-||4.0||-||0.2|
|RH A||P > 560||2009.01||3.5||0.5*||-||6.0*||0.2|
|* HC = 0.4 g/kWh and NOx = 7.4 g/kWh for engines of P > 2000 kW and D > 5 liters/cylinder|
|RC B||130 < P||2012.01||3.5||0.19||-||2.0||0.025|
|R B||130 < P||2012.01||3.5||-||4.0||-||0.025|