Updated September 13, 2018
Locomotive Idling, Air Quality, and Blocked Crossings
When a train is not moving but its engines are running, it
Selected Recent Blocked Crossing Incidents
can present risks and disruptions for the surrounding
There are no national statistics on the frequency or severity
community. Locomotives emit fuel exhaust that degrades
of blocked crossings, but recent incidents have received
air quality and generates noise and vibrations. If the idling
media coverage:
train is stopped at a highway-rail grade crossing, local road
transportation could be significantly impacted, especially if
June 2018: a Canadian National Railway (CN) train
the nearest open railroad crossing is not close by. This
broke down in the town of Barrington, IL, blocking all
could create serious conditions if first responders are unable
four railroad crossings in the town for nearly an hour.
to reach emergencies on the other side of the tracks.
Ambulances transporting victims of a highway collision
were delayed in reaching the hospital (their injuries
Why Do Locomotives Idle?
were non-life-threatening).
Train engines generate thousands of horsepower and take
an hour or more to warm up before they can start pulling
February 2018: a CSX freight train in Tonawanda, NY,
rail cars. This is one reason there is reluctance to turn them
was stopped on a crossing for over two hours due to a
off. Also, particularly relevant for a locomotive attached to
crew shortage.
a train, the brakes on the cars in the train do not work
without power. The locomotive must run to keep the air
April 2017: Senator Charles Schumer and Ulster County
pressure brakes on a train applied (the equivalent of
Executive Michael Hein called on CSX to resolve issues
keeping a car in park). In temperatures below 40 degrees
of trains idling at crossings in Kingston, NY, which cuts
Fahrenheit, the engine has to be kept warm for engine fluids
off certain businesses from the rest of the city entirely if
to work properly, as antifreeze cannot be used in
they are located on dead-end streets.
locomotive engines. Engines are also kept running to
provide air conditioning or heat for the crew, which may be
Possible Responses to Locomotive Idling
aboard even if the train is idling in a yard.
Technology to Reduce Idling Noise/Emissions
Why Do Trains Block Crossings?
The Environmental Protection Agency (EPA) has the
When trains are moving at different speeds or in opposite
authority to regulate locomotive engine noise under the
directions along a single-track rail line, one train will
Noise Control Act (42 U.S.C. §4916) and limit emissions
usually have to wait on a side track or on the nearest two-
under the Clean Air Act (42 U.S.C. §7547). In a 2008
track segment until the other train has passed; if a road
rulemaking (73 Federal Register 37096), EPA set stricter
crosses these tracks, the crossing will be obstructed until it
emissions requirements for locomotive engines built or
is safe for the train to proceed. In many cases, these waits
remanufactured after 2012. It also required new
are planned and meant to be brief, but unforeseen delays
locomotives to be equipped with an AESS (automatic
due to an oncoming or passing train can mean a stationary
engine start/stop system) that will shut down the engine
train must remain in one place for an extended period.
after 30 minutes of idling.
Railroad crews, bound by hours-of-service limits, may not
be permitted to move the train, which then must wait until a
A second device, called an auxiliary power unit (APU), is a
fresh crew can relieve them. Railroads try to schedule crew
small engine that can keep the locomotive’s main engine
changes in convenient locations, but service disruptions
warm, the batteries charged, and the brakes applied, and
occasionally make this impossible, forcing trains to stop
therefore allow the main engine to be turned off without
midway through a journey. Train stoppages are also
endangering the crew or the equipment. An AESS can be
sometimes caused by mechanical failures.
programmed to trigger an APU automatically, without
requiring a rail worker to activate the locomotive on/off
Once a train has been idle for over four hours, or if any cars
switch. EPA opted not to require the use of APUs in the
were removed or added while stopped, regulations require
2008 rulemaking. However, the emission cap regulations
crew to perform an air brake test prior to proceeding to the
offer a fairly strong incentive to install them (40 C.F.R.
next destination, a process that can take several minutes.
92.132(a)(4)).
Freight trains can reach lengths of 2 miles, meaning it can
EPA does not have authority under the Clean Air Act
take several minutes to completely pass a crossing even
(CAA) to require APUs or AESSs to be installed on
when rail traffic is moving. Where equipped, warning lights
existing locomotives. To require railroads to install idle
or gates will engage some time before a train reaches a
reduction equipment on all existing locomotives, which
crossing and will remain engaged for some time after a train
typically have service lives of 40 years, it would be
has passed, somewhat prolonging the traffic obstruction.
https://crsreports.congress.gov
link to page 2 link to page 2 
Locomotive Idling, Air Quality, and Blocked Crossings
necessary to either enact freestanding legislation or to
conducted by CRS, 40 states and the District of Columbia
amend the CAA.
have laws in effect regarding obstructed crossings (Figure
1). Many of these set a time limit on trains to occupy
Surface Transportation Board Remedies
crossings, ranging from as little as five minutes to as much
The Surface Transportation Board (STB) reviews the
as 20 minutes. Other states do not impose a statewide time
construction of new rail lines and transactions involving
limit, but shield railroad employees who block crossings
existing lines. STB can impose environmental mitigation
based on orders from their supervisors.
measures, including those related to locomotive idling, as
part of this review process. For instance, when CN acquired
Figure 1. States with Blocked Crossing Laws
the so-called “J” Line around Chicago in 2008, STB
recognized that a moderately used shortline railroad would
become a heavily used main line track. STB, after a review
from its Office of Environmental Analysis, required CN to
take a number of measures to mitigate the adverse impacts
of increased train traffic on local communities. These
included
construction of two road overpasses to eliminate
blocked crossings at heavily trafficked locations;
accelerated acquisition of new locomotives that would
meet EPA emissions requirements for idling reduction
systems and new procedures to shut down locomotives
Source: Federal Railroad Administration (FRA), Compilation of State
when not in use and when temperatures are above 40
Laws and Regulations Affecting Highway-Rail Grade Crossings, Sixth
degrees; and
Edition, 2013, https://www.fra.dot.gov/StateLaws.
Notes: Congressional Research Service (CRS) verified the status of
measures to keep railroad noise below a certain level for
laws in 12 states not named in the FRA report.
nearby residents by constructing berms or installing
vegetation along the tracks.
However, federal courts have found that some of these laws
Possible Responses to Blocked Crossings
are preempted by one or more federal laws, rendering them
unenforceable. The Federal Railway Safety Act of 1970
2006 Blocked Crossings Study
grants states the ability to enact their own rail safety laws
only if neither the U.S. Department of Transportation
Under a 2005 law, the Secretary of Transportation was
tasked with undertaking a study of the impact of blocked
(DOT) nor the Department of Homeland Security has
issued regulations “covering the subject matter of”
highway-railroad grade crossings on emergency responders.
the state
The final report, published in August 2006 by the Federal
law. States are further restricted from enacting laws that
Railroad Administration (FRA), noted that there is no
burden interstate commerce. Railroad companies have
uniform national data collected on blocked crossings or on
successfully argued in court that laws setting time limits at
crossings are functionally the same as regulating railroad
emergency responder delays.
business practices such as train length and speed or
The report recommended forming close relationships
infrastructure construction, which states are not permitted to
between the railroad and the community so that each may
do.
be made aware of the other’s concerns. In particular, if the
Grade Crossing Improvements
railroad is aware of the locations of critical public safety
facilities, such as fire and ambulance stations, it may be
One effective but expensive way to resolve the issue of
able to adjust the location at which trains stop in order to
blocked crossings is to construct grade-separated
ensure a nearby grade crossing is not blocked. There are
over/underpasses so that rail traffic does not interfere with
some actions railroad companies can take in order to
road traffic. The 2015 surface transportation law, the FAST
Act, added “projects at grade crossings to eliminate hazards
minimize time spent at crossings, including shortening
trains or building additional infrastructure. However, the
posed by blocked grade crossings due to idling trains” in
the list of approved uses for the “Section 130” highway
general tendency has been for railroads to run longer trains
-rail
for economic reasons, which may lead to lengthier delays at
crossing safety program, which receives over $200 million
grade crossings and more blocked crossings when a train is
per year. These funds are then allocated to states by a
stopped. Railroads can also adopt a policy of creating a gap
formula that slightly favors states with a disproportionately
in a stopped train so as not to block a crossing, though the
large share of public grade crossings.
process of creating the gap is time-consuming and would
Certain grade separation projects are also an eligible use of
require the crossing to be closed for that time.
funds from the Better Utilizing Investments to Leverage
State Laws Regarding Blocked Crossings
Development discretionary grant program, known as
There are no federal laws or regulations specifically
BUILD (formerly TIGER), and from the Consolidated
concerning blocked highway-rail crossings. According to a
Railroad Infrastructure and Safety Improvement program
2013 report compiled by FRA and subsequent research
(CRISI), both administered by DOT.
https://crsreports.congress.gov
Locomotive Idling, Air Quality, and Blocked Crossings
IF10978
Ben Goldman, Analyst in Transportation Policy
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 | IF10978 · VERSION 3 · NEW