Noise and Vibration from Idling Locomotives

Table of contents


This document explains noise and vibration from idling locomotives, including:

  • reasons why locomotives idle
  • characteristics of noise and vibration from idling locomotives
  • potential ways of managing noise and vibration impacts

It was developed by the Canadian Transportation Agency's (Agency) Rail Infrastructure Advisory Committee, which is comprised of representatives from the industry, government organizations and the public.


Canada and its communities rely on different modes of transportation to ensure the efficient and economic movement of goods and people. Rail corridors and yards support the competitiveness of Canada in world markets. Canada’s competitiveness also depends on strong municipalities and sustainable municipal growth and development.

Under section 95.1 of the Canada Transportation Act S.C., 1996, c.10 (CTA), railway noise and vibration must be reasonable, taking into consideration three factors:

  1. Level of service obligations

    Level of service obligations refers to the railway company's "common carrier obligations" whereby a railway company must provide adequate and suitable accommodation for the receiving, loading, carrying, unloading and delivery of all traffic offered for carriage on its railway.

  2. Operational requirements

    A railway company's operational requirements include not only those operations necessary to effectively run a railway but also any statutory or legal obligations under other legislation such as the Railway Safety Act.

  3. The area where the railway construction or operation takes place

    This includes the residential, institutional and commercial establishments that are located near to where the railway construction or operation is located.

When the Agency handles a dispute about railway noise and vibration, each case is evaluated on its own merits. Under section 95.3 of the CTA, the Agency may order a railway company to make any changes in its railway construction or operation that the Agency considers reasonable, consistent with the railway company's obligations related to noise and vibration under the CTA. Guidelines for the Resolution of Complaints Concerning Railway Noise and Vibration provides additional information about the scope and statutory provisions concerning noise and vibrations matters.

When challenges surrounding the growth and expansion of rail facilities and municipalities are not identified and addressed at an early stage, issues related to railway noise and vibration may arise. Issues may occur in situations involving new or expanded rail facilities, significant increases or changes in railway operations, and land development near rail operations.

Railway companies should proactively engage municipalities and landowners and share information on expansion of facilities or significant operational changes that may impact the surrounding area. Municipalities should also be proactive in engaging railway companies when planning zoning changes or authorizing new developments near railway operations. Ongoing communication between all parties can help to identify, avoid and address these issues.

Rail operations, by nature, cause noise and vibration. Regardless of the mitigation method selected and its degree of effectiveness in reducing noise levels, in most cases railway noise cannot be completely eliminated and will likely remain audible. It should also be noted that the test to be used by the Agency in the determination of a noise complaint is not whether the level of noise is audible but whether it is reasonable under section 95.1 of the CTA.

Why locomotives idle

Locomotives form a part of every train with the larger and more powerful ones hauling trains over long distances and the smaller ones used in rail yards to move and assemble trains and switch to local industries. They idle for various reasons such as waiting for:

  • oncoming trains to pass or for cars to be switched and/or picked up;
  • mechanical inspections or repairs;
  • inclement weather to pass; and
  • crew changes.

Locomotive engines are not designed to be turned on and off in the same way as automobiles. Engines may be left idling to maintain important safety related functions such as maintaining engine temperature, air pressure for the brake system, the integrity of the starting systems, the electrical system and providing heating or cooling to a train’s crew and/or passengers.

In addition, because locomotive engines use water rather than antifreeze for coolant they cannot be shut down when the temperature drops below 5 ℃. If the water freezes it could cause damage to the engine block.

Characteristics of idling locomotive noise

An idling locomotive creates noise at low frequencies which can travel long distances with little attenuation or reduction in strength. The noise can penetrate through buildings, even when windows are closed, and cause objects to resonate or rattle. Also as the building's sound insulation tends to reduce the impact of higher frequencies, it may exacerbate the effect of low frequency sounds inside the building.

Airborne noise at low frequencies can also induce the vibration of lighter elements of a building, and may be incorrectly perceived as ground-borne vibration.

FAQs: Managing the Impact of Noise and Vibration

How can noise and/or vibration be assessed?

There are various methods to assess different types of noise in different environments.

The Agency's Railway Noise Measurement and Reporting Methodology explains how railway companies, the public and municipalities can assess noise levels from existing rail installations and those under construction. It offers a quick and easy calculation method designed for simple situations involving few sources of noise (Method A), as well as a more complicated methods for calculating noise from multiple sources (Methods B or C). Method B focuses on using noise prediction to assess impacts while Method C uses a combination of field measurements and model predictions to assess noise.

Once the noise is assessed, mitigation may be considered at the source, pathway to receptors, and/or receptors. Possible measures to reduce railway noise must be analyzed on a case-by-case basis keeping in mind cost effectiveness and operational feasibility. Some measures will apply in certain circumstances and not in others. Various mitigation measures are discussed below.

New Locomotive Technologies

Canadian freight and commuter railway companies are constantly renewing their fleets by acquiring new locomotives or refitting existing ones with new technologies that reduce fuel consumption as well as lower air and noise emissions.

Since the late 1970s, locomotives have been equipped with exhaust systems that muffle the sound of the engine exhaust. These systems are limited in size because a larger muffler could increase the overall size of the locomotive and create clearance problems. A larger muffler could also have a negative effect on engine efficiency and regulated emissions controls by introducing back pressure in the exhaust system.

Since the 1980s, new freight locomotives are designed to idle at low engine speeds. These can be as low as 200 revolutions per minute (RPM), in contrast to earlier locomotives which typically idled at 315 RPM. Many of the earlier units have been retrofitted with available low idle speed modifications to reduce idle RPM as much as possible, limiting noise and air emissions.

In addition, anti-idling technologies are being installed on locomotives to save fuel and reduce air emissions. As a secondary benefit, they reduce noise levels by shutting down the engine under certain conditions.

Locomotive external sound levels are regulated by the United States Codes of Federal Regulations (CFR): CFR Title 40 – Protection of Environment – Part 201 Noise Emission Standards for Transportation Equipment.

Automatic Engine Start-Stop (AESS) Control Technology

How it works: AESS turns the locomotive engine on and off to maintain cooling water temperature, lube oil and fuel temperature, air brake pressure, ambient temperature and battery charge within specific parameters.

This technology restarts the main diesel engine automatically when any of these parameters fall below specified thresholds that would impede a quick start or restart. It then automatically shuts down the engine when the parameters are met again after idling for a certain period of time.

Usage: New locomotives are equipped with AESS. This technology is also progressively being installed in existing locomotives as part of a retrofit program prompted by the United States Environmental Protection Agency's emissions compliance requirements.


  • The benefit of this technology is that it can reduce idling times by as much as 40 percent although it still requires the engine to idle between shut down periods.
  • Generally does not permit shutdown when ambient temperature is below 5 ℃. As this technology continues to evolve, it may eventually result in reduced idling times during periods of lower temperatures.

Auxiliary Power Unit (APU) Technology

How it works: APU technology shuts down the main engine during the entire time the locomotive is not in use and a small diesel engine operates to maintain the water, lube oil and fuel temperatures, the air brake pressure, and the batteries charged and ready to start. With the main engine off, the small engine becomes the primary source of noise on the locomotive.

Some systems can also supply electric power for heating locomotive cabs, air-conditioning, lighting, communications and other functions. The generator powers the main engine’s block and fuel system heaters so that it can be started in below freezing temperatures.

Usage: In general, APUs have not been considered technically feasible for freight operations. Modern freight haul locomotives are already fitted with complex locomotive support systems, leaving little or no room to accommodate an APU installation.


  • In 2002, the U.S. Federal Railway Administration conducted stationary locomotive noise tests on an APU technology called Diesel Driven Heating System (DDHS) and found that the locomotive operated at 8 to 10 decibels quieter than when the main engine idledFootnote 1. This is a significant reduction in the noise level even with low frequency noise that results when it cycles the main engines.
  • More expensive than AESS systems but may provide additional benefits and greater fuel economy in certain conditions. For example, unlike AESS systems, APUs can operate in temperatures below 5 oC. However, in some cases the benefits may not be sufficient to pay for the additional cost. Additionally, the complexity of the APU technology is not needed for most of the year when the temperature is mild.
  • To date, railway companies have found that the reliability of APUs is not acceptable, resulting in out-of-service time, maintenance cost and potential risk to the very expensive main engine if the APU fails.

Shore Power Plug-In Technology

How it works: With this option, the locomotive engine is connected to a stationary source of electricity, generally in a railway yard, to warm the main engine by a jacket water heater. Locomotives must be parked near an external high voltage (HV) industrial power source in order to be connected. The system typically requires pumps for cooling water, lube oil and fuel oil heat exchangers, a battery charger to maintain the battery charge and either ground air or a compressor to maintain brake pressure.

Usage: Commonly used with commuter trains, these units are better suited for trains situated near fixed sources of electricity when they are not in use, compared to freight locomotives, which are often used on a 24/7 basis and seldom parked.


  • Effective in winter and summer conditions.
  • Very quiet given they rely on small pumps to circulate the locomotive fluids and the external compressor.
  • The disadvantage of this option is that it requires the installation of dozens of heavy-duty HV connections and cable/plug systems. The long cables can interfere with the normal movement of locomotives being readied for dispatch or servicing in the terminal during routine terminal operations. Another disadvantage is that the maintenance and connecting/disconnecting of the electrical cables must be done. In addition, the cables can be a shock hazard in adverse weather conditions.

Can changes in railway operations be considered to reduce noise and vibration?

There may be opportunities to reduce rail noise by implementing specific operational changes. Any changes must be feasible and take into account the railway company's obligations under the CTA and statutory safety requirements. Meaningful discussions should take place between the railway companies and their customers to determine if operations from a logistical perspective (e.g. scheduling) can be modified to provide some relief to the residents.

Municipalities that are approving the construction of buildings near a rail yard should understand that rail yards cannot easily be reconfigured to reduce noise. Even minor modifications to operations may not be possible.

For example, if locomotives are frequently used throughout the day, parking the engines far from the crew’s office may not be practical. The yards are configured to optimize operations with strategically located support facilities and infrastructure such as fueling areas, layover sites, drip trays, oil interceptors and ground air. Similarly, railway companies use railway sidings to optimize operations for storing rolling stock or to enable trains on the same line to pass. In both situations, prohibiting trains from idling could impede operations and logistics that aim to benefit customers.

Railway operations can also fluctuate depending on customer demand, inclement weather and disruptions to other modes of transportation, resulting in changes to freight logistics and timing. These operational changes can cause noise and vibration levels to fluctuate on a daily basis.

How does a noise barrier work?

A noise barrier is a structure that is designed to block the sounds emanating toward a particular receptor and is typically used to mitigate noise in outdoor amenity areas and the ground floor of buildings. It requires a site-specific design by an acoustic engineer and often consists of a wall or an earth berm (an artificially-constructed mound of earth), or a combination of both. 

The earth that is removed during the construction of a building or a yard can be used to construct a berm.  However, it requires sufficient space to be effective and in a built environment, space may be limited.

Unlike an earth berm, the footprint of a noise wall is relatively small and may be suitable in developed areas where space is limited. To be effective, walls must be located close to the source or receptor, have sufficient density, be high enough to interrupt the sightline from the source to the receptor, and be free of gaps or cracks. Transparent walls, or walls with windows, can reduce the perceived height and permit the transmission of light or covered with plants for added aesthetic appeal.  If a wall is placed half-way between the source and receptor, its effectiveness will be limited as sound waves will go around the barrier.

Noise walls are not technically feasible for multi-storey residential developments since it would have to be extremely high to shield the entire building. Additionally, under certain circumstances they can reflect noise and result in impacts to other nearby receptors.

Incorporating a barrier during the construction phase of a new residential development or railway facility can be an effective alternative to retrofitting a barrier into an existing situation.

What is the acoustic treatment of buildings?

Various acoustic treatments can be included in a building to reduce the transmission of noise such as the addition of insulation, window-glazing or upgraded wall construction. These options can also help to provide insulation from other exterior noises and augment a peaceful environment for the homeowner. To be effective, an appropriate ventilation system such as air conditioning that does not compromise the effect of noise insulation and allows for the windows to be closed in the summer could also be incorporated. It is easier and less expensive to incorporate acoustic treatments during the construction of a building than to do it later, although retrofitting existing buildings may be more cost effective than installing a noise barrier.

Although acoustic treatment may effectively reduce noise exposure within a building, exterior noise will remain unchanged and may limit the enjoyment of the property.  Developers might not incorporate acoustic treatment in the design of new developments unless municipalities impose these measures.

Additional resources

Guidelines for New Development in Proximity to Railway Operations published in 2013 by the Railway Association of Canada and Federation of Canadian Municipalities through the "FCM/RAC Proximity Initiative".


This document has been developed by the Canadian Transportation Agency and members of the Rail Infrastructure Advisory Committee (RIAC) who provided their expertise and valuable feedback on the work draft.  Members come from the railway industry, municipal organizations, and government agencies.

  • Agence métropolitaine de transport
  • Canadian National Railway Company
  • Canadian Pacific Railway Company
  • Federation of Canadian Municipalities
  • Health Canada
  • Metrolinx / GO Transit
  • National Research Council Canada
  • Railway Association of Canada
  • Transport Canada
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