Rail Fleet Decarbonization Opportunity: What Does it Mean for You?

Written by Marcin Taraszkiewicz, P.E., Will Kirby, P.E., and Chris Rand, P.E., HDR, Inc.
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Stadler FLIRT H2

It’s an exciting time for rail fleets and operations. Society’s decarbonization efforts around the globe have created impetus in the rail industry to further reduce its carbon footprint. Technology is improving to make zero emissions a realistic goal. Yet, there is no one-size-fits-all answer to transitioning rail operations to achieve net zero emissions.

It’s an exciting time for rail fleets and operations. Society’s decarbonization efforts around the globe have created impetus in the rail industry to further reduce its carbon footprint. Technology is improving to make zero emissions a realistic goal. Yet, there is no one-size-fits-all answer to transitioning rail operations to achieve net zero emissions.

Passenger and freight railroads have different mixes of diesel vs. electric locomotives and infrastructure. Different parts of the country have various enabling electric power infrastructure and each rail organization has a unique state of readiness for change. Despite the challenges, now is the time to start planning for the future of rail decarbonization in your fleets.


The awareness of human impact on the earth’s environment is at an all-time high. There is considerable pressure in all sectors to minimize or fully eliminate greenhouse gas emissions. Though rail is a cleaner mode of transportation than traditional trucking, freight and passenger railroads are not immune from scrutiny of their efforts to reduce or eliminate greenhouse gas emissions.

There are four main reasons why railroads should seriously consider converting their rail fleets to zero-emissions equipment:

  • Societal Shift: There has been a push for zero-emissions across transportation and other industries, including rail. Investors, clients and the general public are pushing to accelerate the pace of this change.
  • Perception: Although rail produces only 2% of U.S. greenhouse gas emissions, all transportation modes risk being perceived as a “dirty” option so long as carbon-based fuels are widely used.
  • Mandates: Several U.S. states have already implemented or are considering zero-emissions mandates or targets for all land transportation, including railroads. This will force rail operators to plan for decarbonization of their equipment fleets.
  • Equity: Communities near maintenance facilities, rail yards and the right-of-way are disproportionally affected by emissions from locomotives. Reducing and eliminating emissions will not only aid in reducing greenhouse gases but also will improve local air quality and health in these communities.


HDR illustration

There are several approaches to decarbonizing rail fleet operations. One of the oldest means of powering rail vehicles without tailpipe emissions is external power via overhead catenary. This form of power delivery is mature and well understood, but it carries several significant disadvantages that make this a less desirable choice for many rail operations.

Newer technologies, such as batteries and hydrogen fuel cells, offer the promise of emissions-free on-board power with no additional infrastructure requirement along the right-of-way. However, neither of these technologies is yet fully mature, and both currently have limitations that would preclude their use in some applications.

Many long haul or freight operators are looking to interim technologies, such as hybridization, alternative fuels or a combination to reduce emissions until zero-emissions technologies can fully replace current combustion power plants.

Using battery-electric locomotives in freight rail yards and ports is a good example of an interim technology. While battery-electric locomotives fall short on range for heavy long-haul freight, they can reduce emissions in urban areas where many such rail yards exist.

There are many factors that affect the feasibility of each technology—from operating requirements such as speed and payload capacity to environmental conditions including temperature and topography. The local availability of energy sources, either electrical power or hydrogen, can also be a deciding factor in the selection of an appropriate source of power.

When considering the benefits and drawbacks, sometimes the best solution is a combination of two or more technologies, depending on the existing conditions, terrain and other factors.

An example of a successful selection of zero-emissions technology is San Bernardino County Transportation Authority’s Zero Emissions Multiple Unit train, or ZEMU for short. This is a Stadler FLIRT H2 trainset design for commuter train service in the Los Angeles area, the first of its kind in North America to be a hydrogen-battery hybrid vehicle and zero emissions.

While battery power was initially considered the preferred technology for this train, operation simulations showed that this was not an ideal choice for this train primarily due to service range requirements for this vehicle. After an analysis of the service requirements against the capabilities of existing zero-emissions technologies, it was decided that a hybrid system consisting of both batteries and hydrogen fuel cells was the optimal approach to meeting service requirements.

Key Considerations: Supporting Infrastructure and Utilities: Of course, moving from diesel to any other fuel source has ramifications beyond simply purchasing a different locomotive. Planning must consider the supporting infrastructure, facilities and maintenance practices, as well as recharging or refueling strategies and cost modeling for electricity rates.

Infrastructure Considerations: Integrating new technologies into a fleet will likely require existing facilities to be modified—or new facilities built—to support the new fueling or charging requirements. Charge or fueling times (or down time), routes, charging and fueling infrastructure and operations should be modeled and understood with new technologies. For battery-powered trains, it’s not a 1:1 conversion. Charging takes more time than refueling, so organizations often need to purchase more electric vehicles than their combustion fuel counterparts. With hydrogen-powered trains, safety considerations for fueling infrastructure will dictate allocation of space adjacent to the right-of-way that ensures safety while meeting fueling requirements.

Staff Considerations: It’s best to involve staff early in the process so they understand the technology and provide feedback about how changes can be supported in maintenance and operations. Staff can help evaluate how new tasks can be made easier, more productive and safer for the organization, assess configuration of equipment, and facilitate the transition to new operations.

Energy Sourcing Considerations: Operating electric locomotives requires significantly more electricity than a diesel fleet. This means that planners should coordinate very early with the local utility, and possibly the applicable regional transmission organization (or similar), to ensure that the facility can access the required amount of power without disrupting the regional grid.

A thorough study and modeling process of a charging strategy should be conducted to determine the load that will be required from the grid. It should also consider the use of off-peak charging and facility optimization when possible. If the utility is not able to provide the necessary quantity of power without significant infrastructure upgrades, the rail organization can explore installing its own energy generation. Recent legislation has extended tax credits for renewable generation, making this an attractive option for many.

For hydrogen-powered vehicles, the availability of nearby hydrogen production sources is vital. In some areas, hydrogen is already or will soon be produced on a scale that will ensure an abundant and easily obtainable supply. However, many areas still do not have local hydrogen production facilities. Since land transport is currently the main means for transporting hydrogen from its production source to the end user, this might not be a practical, reliable or cost-effective option for many rail operations at this point. Trucking emissions could also offset the benefits of eliminating emissions from the rail equipment.


Rail organizations envisioning a decarbonized future can set themselves up for success with a robust planning process. Best practices include:

Perform service simulations to confirm viability: Implementing new technologies always comes with some risk. It’s important to select the right technology to meet operating service goals. There are a lot of factors that influence the energy requirements, and the best way to determine those requirements is to perform simulations via modeling. The results will help you select the right propulsion technology for your operation.

Engage stakeholders to identify issues: Main stakeholders include regulators, utilities, first responders and the public along the right-of-way. A constant dialog with regulators is critical to communicate expectations and requirements, particularly for safety, to avoid surprises and ensure a timely deployment of new technology trains into revenue service. First responders need to understand the key features of the technology that impact how they handle the equipment in an emergency. The general public should understand that the technology is safe for people living along the right-of-way and appreciate the community benefits of decarbonization.

Involve staff: Staff will need new procedures to support different technologies as well as training for operations and maintenance. New technology equipment requires new processes and new skills. Early engagement and sufficient training time is key for true buy-in and workforce success.


The rail industry has an opportunity to accelerate its decarbonization efforts. The key to capitalizing on this opportunity is effective planning and preparation so that the right technology is selected for the job. In the U.S., there is now funding available to help rail organizations transition to zero-emissions technology.

Plans built by looking at current zero- and low-emission technology opportunities, forecasting what the future will look like, understanding gaps, and then creating a customized strategy will set up railroads to implement a successful fleet decarbonization shift.

Left to right: Marcin Taraszkiewicz, P.E., is HDR’s rail and transit vehicle technology lead. Will Kirby, P.E., is a transportation sustainability leader at HDR. Chris Rand, P.E., is a railroad facilities program manager at HDR.

See Also:

Next-Gen Motive Power

Follow the Megawatt-Hours: Hydrogen Fuel Cells, Batteries and Electric Propulsion

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