Rail Facility Best Practices to Improve Air Quality

Locomotive at a port location
Idle reduction technologies not only reduce emissions but also save fuel.

This page is one in a series of pages that provide information on best practices at ports to reduce diesel pollution and associated health impacts. Select another topic from menu above to explore other sector best clean air practices. 

Rail facilities — including those at ports and other intermodal freight terminals — play an important role for freight operations, the economy and air quality. Emissions sources at rail facilities include switchers and line-haul locomotives. Switchers, also referred to as "yard engines," assemble and disassemble trains. They often operate long hours and have older, high emitting engines. Line-haul locomotives move cargo long distances and are typically larger than switchers and have relatively newer engines. Below are best practices that port and other rail facility operators can adopt to reduce local locomotive emissions.

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Clean Air Best Practices: Appropriateness and Effectiveness

While the examples on this web page are not exhaustive, they are intended to highlight some of the more effective strategies that have been adopted by U.S. ports. The appropriateness and effectiveness of these strategies will vary for different ports based on many factors, including type of operation, fleet makeup, local air quality and pollutant exposure, and community and port priorities. This web page will be updated over time as new clean air practices emerge and information evolves.

Reduce idle emissions from locomotives

Limiting the amount of time switchers and line-haul locomotives spend idling their main engines can result in significant emissions reductions. Idle reduction can also reduce noise and save fuel. Locomotives typically consume between 3 to 5 gallons per hour depending on the ambient temperature.1

Idle emissions can be reduced with technologies such as:

  • Automatic engine shut-down/start-up
    AESS systems control the engine by stopping or starting it without operator action. AESS systems not only turn off the main engine while idling but can re-start the engine when necessary. Re-start of the main engine is typically based on a set time period, engine or ambient temperature, and other parameters (e.g., battery charge).
  • Auxiliary power unit
    APUs are diesel-powered engines (typically 20 to 50 horsepower) that are installed on the locomotive to provide air conditioning, heat, and electrical power to run accessories like lights, on-board equipment, and appliances.
  • Fuel operated heater
    Designed to heat the coolant and oil to allow main engine shutdown in cold temperatures, FOHs do not use a generator to produce auxiliary power. Instead, they circulate and heat the engine coolant and oil to a target temperature of 120°F. FOHs can also provide heat to warm cab and passenger areas.
  • Shore connection system
    SCS systems allow locomotives to “plug into” an electric pedestal to power compatible onboard systems that would otherwise require the main engine to idle.

Rail facilities can also install yard air plants to pre-charge and maintain brake air pressure instead of using the locomotive main engines. These yard air systems are most effective during long periods when a locomotive isn’t doing work. Idle emissions reductions can also be achieved through replacements or upgrades to older locomotives discussed in the section below.

Policy Implementation: Rail facility operators can implement policies to help reduce locomotive idling. For example, operators in cold weather climates can establish a temperature-dependent idling policy where idling (to prevent engine freezing) is only permitted when ambient temperatures approach freezing. Rail facility operators can also implement a warm weather shut down policy that requires or encourages operators to shut down the engines when they are not performing work.

Operational strategies can be implemented as noted below to reduce idle emissions.

  • Configuration and Scheduling: Proper configuration of rail facilities and implementation of optimized locomotive, freight car, and crew scheduling can reduce idling by improving maneuvering, loading, and unloading efficiency.
  • Expanding and Relocating: Port and other rail facility operators can also reduce idling emissions by expanding facilities to increase capacity or by relocating facilities away from congested areas. This can improve track availability and minimize the time locomotives spend waiting to accomplish their tasks.

It is also helpful to keep rail facility staff apprised of idling policies and trained in the proper operation of idle reduction technology to ensure consistent and proper use.

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Technical Resources

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Tips on Performance Targets and Data Collection

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Real-World Examples

Upgrade older locomotives

Newer switchers and line-haul locomotives pollute significantly less than older models, and there are a variety of ways to upgrade them to reduce emissions. In 2008, EPA finalized regulatory standards for diesel locomotives that would reduce particulate matter emissions by as much as 90 percent and oxides of nitrogen emissions by as much as 80 percent when fully implemented. EPA standards also apply for existing locomotives when they are remanufactured. Newer technologies that help locomotives meet these standards include:

  • Verified engine upgrade kits, such as selective catalytic reduction (SCR) systems.
  • Mother-slug combinations of two locomotive units that operate in tandem where only one unit has a combustion engine. Both units are equipped with traction motors that furnish the tractive power to the rail to physically move the train along the tracks. By only using one combustion engine but having the traction power of two locomotives, the mother-slug combination can do more work without added emissions from an additional locomotive(s).
  • GenSet technology that optimizes efficiency by electronically controlling multiple smaller, low-emission diesel electric engines to start or stop to meet power demands during operation.

Alternative fuels are also an option to consider, especially as zero emissions locomotive engines (e.g., electric and fuel cell) come into the market.

Upgrading switchers and line-haul locomotives with newer emission control technologies can play a major role in reducing air pollution at rail facilities. While upgrading any older model will yield emissions reductions and, in most cases, reduce fuel consumption, you can maximize benefits by upgrading the oldest locomotives with the highest annual hours of operation first. You can also maximize benefits by upgrading to engines meeting the most stringent EPA emissions standards. Full replacements (or “repowers”) are generally seen in practice for engines not meeting at least Tier 1 standards due to the technical and physical limitations of the original manufactured engine. For locomotives meeting Tier 1 standards and above, EPA-certified remanufactured kits are more widely available for upgrading engines to meet higher emission standards. Consistent with requirements in EPA’s DERA program, the locomotive you’re upgrading should have operated at least 1,000 hours per year for the past two years and have at least three years of remaining life to maximize emissions benefits.

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Technical Resources

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Tips on Performance Targets and Data Collection

  • Consider setting goals to increase the average Tier performance level of locomotives operating at the rail facility, or the percentage of annual operating hours that are serviced by locomotives with a certain Tier level or higher.
  • Track the annual hours of operation and engine Tier for each locomotive operating at the facility.
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Real-World Examples

Minimize locomotive activity near at-risk populations

Rail facility locomotive operations can have a major impact on the air quality in nearby communities. Rail facility operators can work with community leaders and local planning, health and environmental agencies to identify potential solutions, including the following:

  • Find alternative locations for rail operations that would reduce exposure to rail-related air pollution, as well as reduce the nuisance of rail traffic and noise in populated areas. For example, it may be possible in some cases to relocate maintenance and other locomotive operations within the rail facility but away from potentially vulnerable populations. If it is not possible to shift locomotive operations away from sensitive locations, rail facility operators can prioritize their efforts to reduce idling and upgrade older locomotive engines (discussed above) in those locations.
  • Other ways to mitigate exposure: Rail facility operators can also work with managers of buildings where at-risk populations spend significant amounts of time to implement mitigation strategies to reduce adverse health effects from exposure to air pollution. For example, improved air filtration units can be installed within the buildings, or physical or vegetative barriers can be installed between the railyard and buildings to reduce air pollutants (however, see the factors below concerning physical barriers).

When evaluating existing and alternate locations for rail operations, factors that should be considered include:

  • Distance between the rail facility and locations where potentially vulnerable populations, such as children and the elderly, spend significant amounts of time.  Air pollutants emitted by locomotives can be especially high within about the first 500-600 feet downwind of operations, so special attention should be paid to sensitive locations within this distance. These sensitive locations can include schools, daycares, parks, playgrounds, residences, health care facilities, and other public buildings like libraries.
  • Existence of physical barriers between these sensitive locations and the rail facility. Research suggests that sound walls can reduce concentrations of air pollutants, although the extent of this reduction can vary by the wall height, length and distance from the rail facility. Such barriers may also increase concentrations in the air near the locomotive operations as well as locations upwind and near the edges of the structure. If properly designed, vegetation barriers can be used to reduce air pollution near the rail facility, either alone or in combination with solid structures like sound walls.

Air quality modeling personnel at EPA Regional Offices, and state and local air agencies, can be consulted to help evaluate air pollution impacts to sensitive locations near existing and proposed rail facilities.

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Technical Resources

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Real-World Examples

1 Source: California Air Resources Bord: Technology Assessment – Freight Locomotives (pdf) (4.7 MB, November 2016), and consistent with manufacturer provided EPA certification data.

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Last updated on January 28, 2025