Conventional pollutant emission limits
US Environmental Protection Agency (EPA)
All diesel line-haul, passenger, and switch locomotives that operate extensively within the United States including newly manufactured locomotives and remanufactured locomotives that were originally manufactured after 1972.
US emission standards for railway locomotives apply to newly manufactured as well as re-manufactured railroad locomotives and locomotive engines. The standards have been adopted by the EPA in two regulatory actions:
- Tier 0-2 standards – The first emission regulation for railroad locomotives was adopted on 17 December 19971
- The rulemaking, which became effective from 2000, applies to locomotives originally manufactured from 1973, any time they are manufactured or re-manufactured. Tier 0-2 standards are met though engine design methods, without the use of exhaust gas aftertreatment.
- Tier 3-4 standards – A regulation signed on 14 March 2008 introduced more stringent emission requirements for diesel locomotives of all types — line-haul, switch, and passenger rail.2Tier 3 standards, to be met by engine design methods, became effective from 2011/12. Tier 4 standards, which require the availability of ultra-low-sulfur diesel fuel for exhaust gas aftertreatment technologies, become effective from 2015. The 2008 regulation also includes more stringent emission standards for remanufactured Tier 0-2 locomotives.
Tier 0-2 Standards
Three separate sets of emission standards were adopted, termed Tier 0, Tier 1, and Tier 2. The applicability of the standards depends on the date a locomotive is first manufactured, as follows:
- Tier 0—The first set of standards applies (effective 2000) to locomotives and locomotive engines originally manufactured from 1973 through 2001, any time they are manufactured or remanufactured.
- Tier 1 – These standards apply to locomotives and locomotive engines originally manufactured from 2002 through 2004. These locomotives and locomotive engines are required to meet the Tier 1 standards at the time of the manufacture and each subsequent remanufacture.
- Tier 2 – This set of standards applies to locomotives and locomotive engines originally manufactured in 2005 and later. Tier 2 locomotives and locomotive engines are required to meet the applicable standards at the time of original manufacture and each subsequent remanufacture.
Exempted from the emission standards are electric locomotives, historic steam-powered locomotives, and locomotives originally manufactured before 1973.
The Tier 0-2 emission standards, as well as typical emission rates from non-regulated locomotives, are listed in below. A dual cycle approach has been adopted in the regulation, i.e., all locomotives are required to comply with both the line-haul and switch duty cycle standards, regardless of intended usage. Locomotive engines must also meet smoke opacity standards.
|Tier 0 (1973 – 2001)|
|Tier 1 (2002 – 2004)|
|Tier 2 (2005 and later)|
|Non-Regulated Locomotives (1997 estimates)|
|* HC standard is in the form of THC for diesel engines|
|Steady-state||30-sec peak||3-sec peak|
|Tier 2 and later||20||40||50|
Tier 3-4 Standards
The 2008 regulation strengthens the Tier 0-2 standards for existing locomotives, and introduces new Tier 3 and Tier 4 emission standards:
- Tier 0-2 standards – More stringent emission standards for existing locomotives when they are remanufactured.
- Tier 3 standards – Near-term engine-out emission standards for newly-built and remanufactured locomotives. Tier 3 standards are to be met using engine technology.
- Tier 4 standards – Longer-term standards for newly-built and remanufactured locomotives. Tier 4 standards are expected to require the use of exhaust gas aftertreatment technologies, such as particulate filters for PM control, and urea-SCR for NOx emission control.
The locomotive regulations apply for locomotives originally built in or after 1973 that operate extensively within the United States. Exceptions include (1) historic steam-powered locomotives, (2) electric locomotives, and (3) some existing locomotives owned by small businesses. Furthermore, engines used in locomotive-type vehicles with less than 750 kW total power (used primarily for railway maintenance), engines used only for hotel power (for passenger railcar equipment), and engines that are used in self-propelled passenger-carrying railcars, are excluded from the regulations. The engines used in these smaller locomotive-type vehicles are generally subject to the nonroad engine requirements.
The Tier 0-2 standards apply to existing locomotives of the indicated manufacture years at the time they are remanufactured, beginning from the effective date. The Tier 3-4 standards apply to locomotives of the indicated manufacture years at the time they are newly built or remanufactured.
|Tier 4||2015 or later||2015||0.14f||1.5||1.3f||0.03|
|a – Tier 0-2 line-haul locomotives must also meet switch standards of the same tier.
b – Tier 3 line-haul locomotives must also meet Tier 2 switch standards.
c – 1993-2001 locomotive that were not equipped with an intake air coolant system are subject to Tier 0 rather than Tier 1 standards.
d – As early as 2008 if approved engine upgrade kits become available.
e – 0.20 g/bhp-hr until January 1, 2013 (with some exceptions).
f – Manufacturers may elect to meet a combined NOx+HC standard of 1.4 g/bhp-hr.
|Tier 4||2015 or later||2015||0.14d||2.4||1.3d||0.03|
|a – Tier 1-2 switch locomotives must also meet line-haul standards of the same tier.
b – As early as 2008 if approved engine upgrade kits become available.
c – 0.24 g/bhp-hr until January 1, 2013 (with some exceptions).
d – Manufacturers may elect to meet a combined NOx+HC standard of 1.3 g/bhp-hr.
Tier 3-4 locomotives must also meet smoke opacity standards as specified above. Manufacturers may certify Tier 0-2 locomotives to an alternate CO emission standard of 10.0 g/bhp-hr if they also certify those locomotives to alternate PM standards less than or equal to one-half of the otherwise applicable PM standard. Locomotives may discharge crankcase emissions to the ambient atmosphere if the emissions are added to the exhaust emissions (either physically or mathematically) during all emission testing.
The emission standards apply to new and/or remanufactured locomotives for their useful life. The useful life, generally specified as MW-hrs and years, ends when either of the values (MW-hrs or years) is exceeded or the locomotive is remanufactured. The minimum useful life in terms of MW-hrs is equal to the product of the rated horsepower multiplied by 7.50. The minimum useful life in terms of years is 10 years. For locomotives originally manufactured before January 1, 2000 and not equipped with MW-hr meters, the minimum useful life is equal to 750,000 miles or ten years, whichever is reached first. The minimum emission warranty period is one-third of the useful life (with some exceptions).
Locomotive emissions are measured over two steady-state test cycles which represent two different types of service including (1) line-haul and (2) switch locomotives. The duty cycles include different weighting factors for each of the 8 throttle notch modes, which are used to operate locomotive engines at different power levels, as well as for idle and dynamic brake modes. The switch operation involves much time in idle and low power notches, whereas the line-haul operation is characterized by a much higher percentage of time in the high power notches, especially notch 8.
Locomotive certification and compliance programs include several provisions, including production line testing (PLT) program, in-use compliance emission testing, as well as averaging, banking and trading (ABT) of emissions.
To enable catalytic aftertreatment methods at the Tier 4 stage, the EPA regulated (as part of the nonroad Tier 4 rule) the availability of low sulfur diesel fuel for locomotive engines. A fuel sulfur limit of 500 ppm was effective as of June 2007, and a fuel sulfur limit of 15 ppm was required from June 2012 onwards.