July 5, 2024
Options for Railroad Electrification and Decarbonization
Introduction and Background
calculated using their emissions rates, with those funds
Compared to most other modes of freight and passenger
designated for the acquisition of zero-emission
transportation, railroads consume energy more efficiently
locomotives and infrastructure (or EPA Tier 4
and pollute less. Nevertheless, because most trains rely on
locomotives before 2030).
diesel engines for power, they can generate harmful air
pollutant emissions, especially around rail yards where
Operators may adopt alternative compliance plans with
engines often idle, and greenhouse gases. Reducing
state approval, including the “alternative fleet milestone
emissions from U.S. railroads is of interest to many in
option” where 100% of fleet usage in California would be
Congress as part of the nation’s overall strategy to reduce
from Tier 4 or cleaner locomotives by 2035 and 100% from
air pollution and reach long-term greenhouse gas reduction
zero-emission locomotives or rail equipment by 2047. The
targets.
rule includes conditions for exemptions or extensions and
directs CARB to reevaluate the feasibility of these
The railroad industry has pursued various strategies to
requirements in 2027 and 2032 and adjust if necessary.
reduce emissions. Depending on their operating needs,
railroads are considering mature technologies (e.g., wayside
Because railroads routinely dispatch their locomotives
electric power) or emerging ones (e.g., battery or hydrogen
anywhere on their systems and interchange them with other
power) to accomplish this goal.
railroads, the California requirements could have
implications that reach beyond the state. The largest
The California Air Resources Board In-
railroads may need to replace, rebuild, or redeploy
Use Locomotive Rule and Its Impacts
thousands of locomotives to achieve compliance at a time
Since 2015, newly manufactured or remanufactured
when the industry customarily acquires or remanufactures
locomotives have had to comply with “Tier 4” federal
perhaps a few dozen locomotives per year. CARB has
emissions rules set by the U.S. Environmental Protection
estimated that the rule would cost $15.9 billion in
Agency (EPA); these primarily apply to air pollutants, such
equipment and labor over 25 years, and these costs could be
as particulate matter (PM) and nitrogen oxides (NOx), not
passed on in higher shipping rates. (CARB also estimated
greenhouse gases, like carbon dioxide (CO2). In April 2023,
the value of the rule’s health benefits at $32 billion.)
the California Air Resources Board (CARB) approved
Furthermore, because smaller “short-line” railroads
regulations that would direct railroads to accelerate their
generally purchase older, used locomotives to save on costs,
adoption of zero-emission propulsion technology. The
they may not have the financial wherewithal to make the
California approach differs from federal requirements in
requisite escrow payments and purchase new locomotives if
that it would regulate the operators of existing locomotives
they wish to stay financially solvent (there were 26 such
(as states are blocked from regulating new locomotives by
railroads operating in California in 2021).
federal law), and it would also apply to greenhouse gases.
These new regulations may prompt technological advances
The rule, which requires a waiver from the EPA before it
and expanded production of zero-emission rail equipment.
can go into effect, has already been challenged in court.
Under the proposed rule,
Opponents argue, among other points, that federal law vests
•
exclusive jurisdiction over interstate rail transportation with
starting in 2024, locomotives would not be permitted to
the Surface Transportation Board, preempting state laws.
idle for longer than 30 minutes (subject to exceptions);
Railroads have successfully sued to make other state laws
•
and regulations governing rail transportation unenforceable
starting in 2030, only locomotives with an original
on similar grounds.
engine build date less than 23 years old would be
allowed to operate in California, excepting those that
Wayside Electric Power
meet EPA Tier 4 emission standards, that are operated
Electric railroad technology has existed since the late 19th
in a zero-emission configuration while in California, or
century. Fully electric trains produce no emissions of their
that have primary engines below a specified power
own, generally drawing power from overhead wires (an
output in megawatt-hours (MWh);
overhead catenary system, or OCS) or from an electrified
•
third rail running alongside the tracks. Both methods
all passenger and switcher locomotives built in 2030 or
require the construction of electric power substations along
beyond, and all line-haul freight locomotives built in
the route, adding to up-front infrastructure costs.
2035 or beyond, must operate in a zero-emission
configuration while in California; and
Electrification can also provide operational benefits.
•
Electric locomotives have fewer moving parts than diesel
all operators of non-zero-emission locomotives must
locomotives, making them easier to maintain and more
make payments into escrow accounts, in amounts
https://crsreports.congress.gov
Options for Railroad Electrification and Decarbonization
reliable, reducing maintenance costs. They also generate
motion along third rails or overhead wires, then run on
more power relative to their weight than diesel engines,
battery-only power in non-electrified territory.
enabling higher maximum speeds and faster acceleration
and deceleration, potentially reducing travel times. This is
Hydrogen Power
especially true when each car in a train contains its own
Hydrogen fuel cells use either liquid or gaseous hydrogen
traction motor in what is known as “multiple unit (MU)”
reacting with oxygen to produce electricity; the reaction
configuration, distributing mechanical power to more sets
produces only heat and water as by-products. Some internal
of wheels than those on a single locomotive.
combustion engines can also use hydrogen fuel (instead of
diesel), producing no carbon emissions during operation.
In the United States, electric trains tend to be used primarily
However, today, the manufacture of almost all industrial
for passengers, not for freight. The rapid acceleration and
hydrogen produces greenhouse gases.
high speeds afforded by electric traction motors are not
seen as providing enough benefit to freight traffic to justify
The Federal Railroad Administration (FRA) and Sandia
the cost of installing or modifying the necessary
National Laboratories published a study in 2021 that
infrastructure. Freight trains that make use of double-
reported, in part, that hydrogen fuel cell power presents
stacked container cars can be compatible with overhead
many of the same advantages as battery electric power but
wires, but many existing bridges and tunnels do not have
has faster refueling compared to batteries. The study also
sufficient clearance to accommodate double-stacked
found that, “[g]iven the need for refueling infrastructure,
containers and overhead wires without potentially costly
hydrogen fuel cell powered locomotives would be most
modifications. Furthermore, while diesel locomotives can
useful initially in applications that have limited geographic
effectively operate nationwide, electric locomotives would
range.” Some California passenger railroads have begun
be unusable on unelectrified portions of the network,
procuring hydrogen-powered railcars, and some freight
reducing flexibility. Because most passenger rail routes in
railroads have successfully converted long-haul diesel
the United States share tracks with freight trains, most of
locomotives to run on hydrogen power.
the rail system continues to rely on diesel power.
Federal Support
Electric trains can still consume power generated by fossil
No federal statute or regulation prioritizes or promotes
fuels, and technologies that reduce or eliminate carbon
railway electrification or decarbonization, and freight
emissions do not necessarily entail full electrification.
railroads typically do not receive federal funding as they are
Carbon emissions, it is argued, can likely be reduced by
financially self-sufficient private businesses. Projects to
diverting higher emission highway and airplane traffic to
electrify or decarbonize rail lines may be eligible for
rail without any shift to alternative power sources.
several different federal grant programs administered by
Battery and Battery-Hybrid Power
FRA or the Federal Transit Administration, but no federal
funds have been explicitly directed toward rail
Rechargeable batteries could be one alternative to
electrification since the New Haven-Boston segment of
electrification. Trains could be entirely battery powered,
Amtrak’s Northeast Corridor was electrified in 2000. Other
producing no emissions when operating, or use a
federal programs to support deployment of battery charging
configuration known as hybrid diesel-electric battery
infrastructure or hydrogen fuel, such as those funded by the
(HDEB) where a diesel engine also charges a battery
Infrastructure Investment and Jobs Act of 2021 (P.L. 117-
similar to that in a gasoline hybrid automobile. Advantages
58) or the unofficially named Inflation Reduction Act of
of battery power include minimal need for new or modified
2022 (P.L. 117-169), have generally been targeted to
infrastructure, though charging stations would be needed
highway uses, not railroads. Recent examples of federal
for 100% battery operations, and electrical transmission
support for rail electrification or alternative fuels include
lines may require upgrades. Even with recent advances in
the following:
chemistry and manufacturing, the added weight of batteries
detracts from their ability to efficiently move an entire train.
• Congress appropriated $2.5 million in FY2023 FRA
funding to “continue ongoing research, development,
Several battery-hybrid locomotive models have been built
and testing on innovative technologies and solutions for
and demonstrated, but comparatively few are in active
low- or no-emission alternative fuels for locomotives,
service. Manufacturers have also introduced pure battery-
engine improvements, and motive power technologies.”
powered locomotives that can run in tandem with a
conventional diesel-electric locomotive, effectively creating
• FRA awarded $35.6 million in FY2022 Consolidated
an HDEB system across two locomotives. These units can
Rail Infrastructure and Safety Improvements grant funds
maintain full output exclusively on battery power for 30-40
for the procurement of six new battery-electric
minutes at a time. Consequently, pure battery operations
locomotives and eight diesel-to-battery conversions, all
may be impractical for most long-haul operations owing to
for freight switching operations.
the number of chargers that would be needed over the route.
• Amtrak is also using federal funds to replace some of its
Some commuter rail agencies have begun procuring
railcars and locomotives with new trainsets, some of
battery-powered railcars. One application of battery power
which will be equipped with dual-mode diesel-electric
already deployed in Germany and Japan, and proposed in
and diesel-battery hybrid locomotives.
the United States, is the addition of batteries to
conventional electric trains in a battery electric multiple
Ben Goldman, Analyst in Transportation Policy
unit (BEMU). BEMUs can charge their batteries while in
IF12707
https://crsreports.congress.gov
Options for Railroad Electrification and Decarbonization
Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff to
congressional committees and Members of Congress. It operates solely at the behest of and under the direction of Congress.
Information in a CRS Report should not be relied upon for purposes other than public understanding of information that has
been provided by CRS to Members of Congress in connection with CRS’s institutional role. CRS Reports, as a work of the
United States Government, are not subject to copyright protection in the United States. Any CRS Report may be
reproduced and distributed in its entirety without permission from CRS. However, as a CRS Report may include
copyrighted images or material from a third party, you may need to obtain the permission of the copyright holder if you
wish to copy or otherwise use copyrighted material.
https://crsreports.congress.gov | IF12707 · VERSION 1 · NEW