Long Freight Trains: Ensuring Safe Operations, Mitigating Adverse Impacts (2024)
Chapter: 3 Technology for Controlling Long Trains
3
Technology for Controlling Long Trains
This chapter explains the role of locomotive technology and operations in the evolution of the systems used to control trains, including long trains. Class I railroads now rely on engineer-assist systems to operate all freight trains in North America. These systems use locomotive dynamic brakes as the primary method for train braking. However, air brakes are also used in steep terrain and slow-speed maneuvers and are still the primary emergency braking requirement. The chapter also describes results of the Federal Railroad Administration (FRA) very long train technical reports to test air brakes and dynamic brakes on trains with more than 200 cars, and it includes a discussion about electronically controlled pneumatic (ECP) brakes. The chapter concludes with a discussion of the continuing crew member communication challenges presented by long trains as well as brief consideration of Positive Train Control (PTC).
LOCOMOTIVE TECHNOLOGY
Technology has and is playing a major role in enabling the operation of longer trains. The key technology that helps control long trains is the use of distributed power (DP) locomotives, with multiple sets of locomotives spread throughout the train. These groups of locomotives can be separately controlled to minimize in-train forces. To make this task easier, engineer-assist systems either coach engineers on how to control all engines or automatically control all locomotives as a modern cruise control. However, as with many technologies, engineer-assist systems still have problems, and engineer training is critical for maintaining safe operations. Due to the
reliance on engineer-assist systems, the committee learned that engineers may not be getting as much experience manually operating trains with DP locomotives.
Distributed Power
As noted in Chapter 2, distributing locomotives throughout a train reduces both pulling (draft) and pushing (buff) forces within the train. DP locomotives can reduce these forces when spaced appropriately throughout the train to separately apply power, apply air brakes, and/or apply dynamic brakes. Their application can make a single long train handle like several smaller trains.1 A train operating with DP may be configured with mid-consist locomotives (sometimes at two places) and/or one or more locomotives at the rear of the train. Some railroads prefer using locomotives at the back of the train for more pushing power in certain terrains.2 DP units also provide additional air compressor capacity by charging the brake pipe from several locations along the length of the train and by providing additional locations for train air brake applications, thereby further enhancing braking performance.3,4
Without DP locomotives (all engines at the front of the train), the buff and draft forces immediately behind the locomotives will increase with train length and weight. This results from the entire train pushing on the first car of the train when using dynamic brakes and from the entire train being pulled from the first car in a train without DP locomotives. For sufficiently long and heavy trains without DP locomotives, these draft forces may approach the force limits of the couplers between rail cars. Longer trains without DP locomotives will also require more time for propagation of air brake applications.5
Communication technology used to control DP locomotives in the train is known as LOCOTROL (an abbreviation of “locomotive” and “control”).6 This merits mentioning because, in the past, tunnels and rough terrain created impediments for maintaining communications between the controlling locomotive at the front of the train and the DP locomotives
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1 Ibata, D. 2019. “Train Make-Up 101: Or How to Not Let This Happen to You.” TrainsMag.com, July.
2 BNSF presentation to committee, April 2023.
3 Vantuono, W.C. 2011. “The Long and the Short of Distributed Power.” Railway Age, August 1. https://www.railwayage.com/cs/the-long-and-the-short-of-distributed-power.
4 Aronian, A., K. Wachs, S. Bell, and D. Peltz. 2011. “Long Train Testing and Validation at Canadian Pacific.” International Heavy Haul Association Conference, June, Calgary, Canada.
5 Vantuono, W.C. 2011. “The Long and the Short of Distributed Power.” Railway Age, August 1. https://www.railwayage.com/cs/the-long-and-the-short-of-distributed-power.
6 LOCOTROL was developed by Wabtec but is used on both GE/Wabtec and EMD/Progress locomotives. Wabtec presentation to committee, May 2023.
and end-of-train (EOT) devices. Although many technological solutions were tried, including repeaters spaced out along the right-of-way and inside tunnels,7 the problem led the Federal Communications Commission (FCC) in 2010 to authorize an increase in EOT power output from 2 to 8 W.8 Concurrent with the advent of PTC, the changes caused a more robust and dependable communications protocol, LOCOTROL Expanded Architecture, or LXA,9 to be introduced.10,11 All Class II railroads are now in the process of updating locomotives with this new communications protocol, which will increase the reliability of LOCOTROL communications and allow railroads to place DP locomotives in up to four locations throughout a train. This development should be beneficial for control of longer trains.12
While distributed power can reduce in-train forces and improve train handling and braking performance on longer trains that are properly constructed, the magnitude of its effect on train safety, including the safe operations of longer trains, is an ongoing area of research. Researchers at the University of Illinois at Urbana-Champaign (UIUC) have conducted statistical analyses of accident records to investigate the effect of DP on derailment frequency and severity for various train types. The analyses are possible because FRA accident records indicate the number of locomotives at the front, middle, and rear of the train, allowing incidents to be classified as conventional trains with all locomotives at the front or DP trains with locomotives at intervals. For all FRA-reportable mainline and siding derailments from 2001 to 2022, the UIUC researchers found that 81% involved conventional trains with locomotives only at the front, while the remaining 19% involved DP trains.13 Note, the traffic data required to normalize derailment counts by train-miles of DP and non-DP trains were not available.
The UIUC researchers examined the relative severity of derailments involving DP and non-DP trains. They found that the median train length and weight of DP trains was greater than that of non-DP trains. They also found that DP trains derail at a higher speed than non-DP trains. Based on these differences in train length and weight and speed at the time of derailment, one would expect that derailments involving DP trains will be more
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7 Some railways initially installed radio repeaters on long trains to mitigate signal loss, especially in tunnels and mountainous areas. Federal Railroad Administration (FRA). n.d. “Stakeholder Perceptions of Longer Trains.” https://railroads.dot.gov/elibrary/stakeholder-perceptions-longer-trains (accessed May 3, 2024).
8 CN presentation to committee, April 2023.
9 For more information, see https://www.wabteccorp.com/digital-intelligence/next-generation-distributed-power-activating-the-future-of-freight-rail-through-enhanced-communications.
10 Wabtec presentation to committee, May 2023.
11 Class I railroads, presentations to committee, March and April 2023.
12 Ibid.
13 Christopher P.L. Barkan et al., presentation to committee, May 22, 2023.
severe on average (i.e., derailing more cars). However, when the researchers compared the median number of cars derailed per derailment, they did not find a statistically significant difference in derailment severity among accidents involving DP and non-DP trains. These results suggest that, even though DP trains tend to be heavier and longer than non-DP trains, they may be helping to reduce derailment severity by helping to manage in-train forces and handling challenges of longer trains.
Engineer-Assist Systems
To save fuel and maintenance costs, railroads have relied on greater use of dynamic brakes through engineer-assist systems. LEADER (New York Air Brake)14 and TripOptimizer (Wabtec)15 are two competing engineer-assist systems. Initially, these systems were designed for energy use management because of their reliance on dynamic brakes as opposed to air brakes to reduce fuel consumption. Such systems advise, or even control, throttle and dynamic brake actions and recommend selected air brake applications depending on the grade, train speed, train makeup, and the territory ahead.16 Both systems are used on conventional and distributed power trains and provide engineers information about the train so they can mitigate the potential excessive forces involved. With more widespread implementation of DP locomotives and longer trains, the engineer-assist systems have taken on an additional objective of managing the use of DP units to minimize in-train forces.17 These systems are also evolving into cruise control or autopilot systems, and fully automatic operations are being tested in the United States.18 Certain lines in Australia already support fully autonomous freight train operations.19
The use of engineer-assist systems does have some limitations. Current U.S. systems can recommend but not control air brake applications, so the engineer-assist systems either rely on dynamic brakes alone or signal the engineer to initiate train air brake applications as necessary.20 Distributed power locomotives either can be set up to duplicate the setting on the
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14 Products, New York Air Brake, and milosms2015. “LEADER.” NYAB Products, March 13, 2015. https://www.nyabproducts.com/leader.
15 Wabtec Corporation. n.d. “Trip Optimizer™.” https://www.wabteccorp.com/digital-intelligence/energy-management/trip-optimizer (accessed May 3, 2024).
16 New York Air Brake and Wabtec presentation to committee, May 2023.
17 Ibid.
18 Luczak, M. 2022. “Watch: Testing New Wabtec Trip Optimizer Feature.” Railway Age, September 8. https://www.railwayage.com/freight/class-i/watch-csx-testing-new-wabtec-trip-optimizer-feature.
19 “Self-Driving Trains: The World’s Heaviest Robot.” June 23, 2023. https://www.knorr-bremse.com/en/magazine/self-driving-trains-the-worlds-heaviest-robot.json.
20 New York Air Brake and Wabtec presentations to committee, May 2023.
lead locomotives (synchronous) or can be controlled separately (asynchronous or “fenced”). However, DP units are not allowed to apply dynamic brakes when the head-end units are in power. The opposite asynchronous scenario is allowed (lead units in braking or idle while DP units in traction) and is frequently used by train crews to keep the slack in the couplers between rail cars bunched in undulating territory.21
Although DP units and engineer-assist systems reduce in-train forces, it should be noted that FRA has advised railroads that their use alone is not enough to avoid derailments. FRA’s April 2023 advisory emphasizes that using DP units “should not be considered a replacement for proper train car placement and makeup,” and notes that several in-train force derailments occurred even when DP unit power was used. In some cases, the engineer-assist system was in control of the train.22
Engineer-assist systems have proven so useful that many railroads encourage—and some require—that engineers rely on them whenever possible.23 Engineers are sometimes required to take manual control when engineer-assist systems are not operating properly, when the train is moving at low speeds, or when urgent braking action is needed.24 The increasing reliance on autonomous systems may have some effect on engineers’ skill level for handling long manifest trains without the aid of engineer-assist systems. Engineer training is discussed in Chapter 5.
BRAKING SYSTEMS
Controlling freight trains before the advent of air brakes was a dangerous business. Trains were slowed using manual brakes that required brakemen to move from car to car while the train was moving to apply hand brakes on each car with unreliable results and much loss of life. The invention of the air brake system, first patented by George Westinghouse in 1869, helped control train speed and is still in use today.25 Locomotive dynamic brakes came into use with the shift from steam to diesel-electric locomotives. Their
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21 T. Dick, background for technology questions, May 16, 2023.
22 FRA. 2023. “Safety Advisory 2023-02; Train Makeup and Operational Safety Concerns.” Federal Register 88:21736. https://www.govinfo.gov/content/pkg/FR-2023-04-11/pdf/2023-07579.pdf.
23 Committee members heard conflicting reports from Class I railroads on the use of air brakes in conjunction with TO and LEADER. Some railroads encourage engineers to manually control trains when needed, while others reprimand engineers for switching from automatic to manual operation because it increases fuel costs.
24 SMART and BLE-T presentations to committee, January 19, 2023.
25 Humphrey, A.L. 1914. “Forty-Five Years of Air-Brake Evolution.” Scientific American 110(25):498–511. Although train air brakes are often referred to as automatic brakes, the term “train air brakes” or simply “air brakes” is used here to avoid confusion with actual automatic systems.
first widespread adoption was for moving trains in mountainous areas.26 Today, the majority of trains run by the Class I railroads are operated by engineer-assist systems that use locomotive dynamic brakes supplemented by the use of air brakes as needed.
Train Air Brakes
Train engineers use train air brakes to apply brakes on each locomotive and on each car in the train to slow or stop the train. Each freight car contains the necessary equipment to stop itself using compressed air stored on the car in air reservoirs.27 The air in each car is supplied by the locomotives. When all the cars are connected (through the connecting couplers known as glad hands), the brake pipes on each car are connected to a continuous air line (or “trainline”) from the leading locomotive to the end of the train. For typical freight operations, air compressors on the locomotives charge the train air brakes through the air brake pipe to a pressure of 90 psi.28
To release the train brakes, the engineer raises the pressure in the trainline, which is sensed by each car’s control valve, and the compressed air in the brake cylinder is released and the reservoirs are recharged back to operating pressure. Should the brake pipe have a sudden and rapid drop in pressure (such as when a coupler breaks and the brake pipe connection is broken), the control valves on each car sense this and initiate an emergency brake application where compressed air from a larger emergency reservoir tank on each car is directed to the brake cylinder, creating the maximum braking force possible for each car on the train.29
One drawback with this system is that although the engineer can gradually apply brake force using successive air pressure reductions, the system does not allow for the gradual release of the brakes. There is no way to ease off the brake; only a full brake release can occur. As a result, once brakes are applied, releasing them and then reapplying them before the air reservoirs on each car have had time to refill reduces the effectiveness of the train air brakes.30 To control train speed on a descending grade, the
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26 McGonigal, R.S. 2024. “Dynamic Braking 101.” Trains, February 6. https://www.trains.com/trn/train-basics/abcs-of-railroading/dynamic-braking-101.
27 Transportation Safety Board of Canada. 2022. “Locomotive and Freight Car Brakes.” March 31. https://www.tsb.gc.ca/eng/medias-media/fiches-facts/r19c0015/r19c0015-20220331-3.html, p. 209.
28 Ibid.
29 PRC Rail Consulting Inc. n.d. “North American Freight Train Brakes.” The Railway Technical Website. http://www.railway-technical.com/trains/rolling-stock-index-l/train-equipment/brakes/north-american-freight.html (accessed May 3, 2024).
30 Transportation Safety Board of Canada. 2022. “Locomotive and Freight Car Brakes.” March 31. https://www.tsb.gc.ca/eng/medias-media/fiches-facts/r19c0015/r19c0015-20220331-3.html, p. 209.
engineer may have to apply the air brakes and locomotive dynamic brakes to keep control of the train.31
Locomotive Independent Brakes
Locomotives are also equipped with an independent air brake system, which is separate from the normal train air brakes.32 Although the independent direct air systems allow for faster braking operations, they are typically used for situations involving locomotives, such as parking maneuvers, rather than those with entire freight trains.33 Locomotive dynamic brakes provide greater overall braking power than the locomotive independent brakes. However, locomotive independent brakes may be used in emergency situations.
Locomotive Dynamic Brakes
Locomotive dynamic brakes are powered by the electricity generated by the kinetic energy of the train in motion. Locomotive dynamic brakes can be gradually applied and released. Because no mechanical friction is used to impede the rolling of locomotive wheels, there is little wear on the wheels and no wear of the brake shoes.34
However, while dynamic brakes are useful to control train speed, their braking power declines at speeds below 9 mph. Engineers can use dynamic brakes in emergency brake applications aboard the locomotive in the lead position; however, remote locomotives in the consist default to 45 psi brake cylinder pressure in an emergency and lose dynamic braking effort. Train air brakes will usually stop trains quicker than dynamic brakes in emergency situations.35 In addition, because the braking action takes place only on the locomotives, dynamic braking affects in-train forces differently than air brakes. Dynamic braking force is concentrated on the cars immediately behind locomotives. As trains have grown longer, the effect of dynamic
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31 This problem is somewhat alleviated in passenger cars, which can have graduated release that lets engineers reduce brake action without completely releasing the train brakes.
32 Transportation Safety Board of Canada. 2022. “Locomotive and Freight Car Brakes.” March 31. https://www.tsb.gc.ca/eng/medias-media/fiches-facts/r19c0015/r19c0015-20220331-3.html, p. 209.
33 Ibid.
34 One exception is where excess braking force results in wheel sliding, but modern systems prevent wheel slip from happening. Also, using dynamic brakes results in less wear on brake shoes of cars than using train air brakes.
35 PRC Rail Consulting Inc. n.d. “North American Freight Train Brakes.” The Railway Technical Website. http://www.railway-technical.com/trains/rolling-stock-index-l/train-equipment/brakes/north-american-freight.html (accessed May 3, 2024).
brake use on in-train forces has increased.36 Using DP locomotives can transfer some of the dynamic braking forces to other parts of the train, but braking effort is still concentrated immediately behind both the lead and the DP locomotives.37 This concentration of braking power is based on how many cars are being held back by locomotives, with the cars nearest the locomotive having the highest buff forces acting on them.38
Train Brake Applications
Although dynamic brakes are the primary method of train braking, air brakes are still needed for extra braking power on steep grades, for low-speed braking, and for stopping trains in an emergency. This is because train air brakes provide a fail-safe braking mechanism, because dynamic brakes lose braking power at slower speeds and because dynamic braking power is limited by the number of locomotive axles on a train. For these reasons, air brakes are required on all freight trains. They are fail-safe because any severing of the trainline will result in an emergency brake application. Such separations can result from a broken knuckle or a derailment.
Serial Application
A serious problem with the use of train air brakes is the amount of time it takes for the air signal initiated by the engineer at the locomotive to travel through the brake line from the front to the rear of the train. The delay between brakes applying on the front of the train and the rear of the train naturally increases with train length and can result in extreme buff (compressive) forces at the front of the train.39 This has been mitigated by the introduction of the EOT device, which allows engineers to release air from both ends of the train in an emergency, thereby reducing in-train forces caused by braking from the front end only.40 The use of DP locomotives (with LXA communications) has also improved this situation by controlling brake pipe reductions at remote locomotive locations, decreasing the
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36 Ibata, D. 2019. “Train Make-Up 101: Or How to Not Let This Happen to You.” TrainsMag.com, July.
37 Ibid.
38 Ibid.
39 Vantuono, W.C. 2011. “The Long and the Short of Distributed Power.” Railway Age, August 1. https://www.railwayage.com/cs/the-long-and-the-short-of-distributed-power.
40 “End-of-Train Devices.” 49 C.F.R. Part 232, Subpart E. https://www.ecfr.gov/current/title-49/part-232/subpart-E (accessed May 14, 2024).
time it takes for the entire train to reach full braking.41,42 This is especially important for quickly and safely stopping a train with an emergency brake application.
No Partial Release
While most passenger cars are equipped for partial (or graduated) release of train air brakes, freight train cars are not. In situations where brakes must be released and reapplied, retaining valves (retainers) on each car can be adjusted to retain a limited amount of braking power while train air brakes are recharged.43 Retainers were used frequently prior to the adoption of very effective dynamic brakes, but they are seldom used by railroads today.44 The time to set and release retainers has become prohibitive with today’s longer trains. In situations where train air brakes are needed to hold a train on a hill, a release of brakes often must be followed by an emergency application and requires setting hand brakes until the entire train air brake system can be fully recharged.
Recharge Time
With longer trains, the time needed to completely recharge train air brakes has increased as much of the air supplied to the system may potentially leak out before it reaches the end of the train. Cold weather can also increase rechange time due to increased leakage.45 DP locomotives placed strategically throughout the train may not reduce leakage but can help recharge the air in the train.46
Emergency Brake Applications
In emergency situations, engineers can initiate a desired emergency air brake application that will cause each car to exert the maximum braking pressure
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41 Distributed power is the placement of additional locomotives at the rear and/or interior of the train that are controlled by the engineer in the leading locomotive.
42 Aronian, A., K. Wachs, S. Bell, and D. Peltz. 2011. “Long Train Testing and Validation at Canadian Pacific.” International Heavy Haul Association Conference, June, Calgary, Canada.
43 Krug, A. 2019. “North American Freight Train Brakes.” The Railway Technical Website. 2019. http://www.railway-technical.com/trains/rolling-stock-index-l/train-equipment/brakes/north-american-freight.html.
44 Ibid.
45 CN presentation to committee, April 2023.
46 In addition to DP locomotives, some railroads have used “distributed braking box cars” with air compressors to help charge train air brakes.
available.47 Emergency brake application can be needed because of unforeseen obstructions, grade-crossing accidents, and so on and will result in the serial application of brakes as described above. Emergency brake applications are more complex in long trains because long trains are likely to have multiple DP units.48 During emergency braking, emergency brake application will cause power knockdown and idle the DP locomotives. Dynamic brake effort would be retained, but power (throttle) cannot be adjusted.
Undesired Emergency Brake Application
Train air brake systems are designed so that broken equipment, derailments, malfunctioning brake valves, broken trainlines, and so forth that independently reduce trainline brake pressure rapidly to zero will cause an undesired emergency (UDE) brake application.49 The unintended (undesired) application of train emergency air brakes is a high-risk situation. During a UDE brake application (such as in the case of a train separation due to a broken knuckle or a malfunctioning brake valve), the engineer is not in full control of the train air brake system because the cars are automatically applying their emergency brakes for a brief time before the engineer is aware an emergency brake application has occurred. In addition, the train is at increased risk for high buff or draft forces during a UDE brake application, potentially high enough to cause a broken coupler knuckle or a derailment.
Longer Trains and Emergency Brake Applications
Longer trains are more at risk of experiencing a prolonged information gap between UDE brake application and engineer awareness because the incident initiating the brake pipe pressure drop may occur at any position in the train. In addition, UDEs are especially problematic for four reasons, as highlighted in a 2022 FRA Safety Advisory. First, even if the train remains intact and undamaged, recharging the train air system can be time
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47 Transportation Safety Board of Canada. 2022. “Locomotive and Freight Car Brakes.” March 31. https://www.tsb.gc.ca/eng/medias-media/fiches-facts/r19c0015/r19c0015-20220331-3.html, p. 209.
48 Emergency brake applications (especially undesired ones) can create severe in-train forces due to lags in brake applications and variation in car braking forces. As a result, engineers often release locomotive independent brakes and apply power to keep the train stretched out while it is stopping to prevent cars from piling up in a derailment. If stopping as quickly as possible is more important, engineers can use dynamic brakes in addition to the train air brakes. DP can be used similarly as deemed appropriate (added power or dynamic brake) by the engineer.
49 Carlson, F.G. 1990. “Undesired Emergency Brake Applications: Transportation Test Center UDE Tests.” Report No. R-761. Association of American Railroads. https://railroads.dot.gov/elibrary/undesired-emergency-brake-applications-transportation-test-center-ude-tests.
consuming. Second, if a train has an emergency application on a grade (desired or undesired), hand brakes must be tied down to hold the train while the brake system is being recharged.50 There is also a Canadian Rail Operating Rule, “Securing equipment after an emergency brake application on grade,” which requires applying hand brakes to secure and recharge the train after an emergency brake application.51 Third, as the train is braking under maximum braking force, high in-train forces may be generated between cars, increasing the risk of derailment of the train. Finally, after a UDE brake application, a train must be thoroughly inspected to find the cause of the UDE, to identify any damage or derailment caused by the UDE, and to make necessary repairs. The latter two problems are made more difficult and time consuming by longer trains, because train crews must travel greater distances to complete the inspections and manually apply the hand brakes.52 The increased risk for a long train is that the crew must have sufficient time to apply the necessary hand brakes to hold the train in case the air brakes release or there is a depletion of average brake cylinder pressures, sufficient to hold the train on the descending grade. A long train on a grade will require more hand brakes to be applied to secure the train, requiring more time from the crew. Environmental conditions, such as heavy snow, wind, or rain, may also increase the time needed to apply the hand brakes.
Unintended Brake Release
In certain circumstances, train air brakes can release on their own with no action from the engineer. This can result in a high-risk situation for trains stopped on a grade. When this happens, an emergency brake application should be made, and enough hand brakes should be applied to hold the train on the grade.53 An FRA safety directive also states that train crews should not expect a service or emergency brake application to be indefinitely maintained because air eventually leaks out of the brake system.54
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50 FRA. 2022. “Safety Advisory 2022-02; Addressing Unintended Train Brake Release.” Federal Register 87:80256. December 29. https://www.federalregister.gov/documents/2022/12/29/2022-28336/safety-advisory-2022-02-addressing-unintended-train-brake-release.
51 Canadian Rail Operating Rule (CROR) 66.
52 GAO (U.S. Government Accountability Office). 2023. “Rail Safety: Freight Trains Are Getting Longer, and Additional Information Is Needed to Assess Their Impact.” June 1. https://www.gao.gov/products/gao-19-443.
53 FRA. 2022. “Safety Advisory 2022-02; Addressing Unintended Train Brake Release.” Federal Register 87:80256. December 29. https://www.federalregister.gov/documents/2022/12/29/2022-28336/safety-advisory-2022-02-addressing-unintended-train-brake-release.
54 Ibid.
Train Brakes in Operation
Application of train air brakes has a significant impact on in-train forces. During regular braking, the engineer applies a combination of dynamic brakes and train air brakes to control the speed of the train or, if needed, to bring a train to a stop. Ideally, engineers endeavor to keep trains either completely stretched55 or completely bunched.56
Today most railroads employ engineer-assist programs that rely primarily on dynamic brakes (and bunching trains) to control speed. This saves fuel by not having to drag a train with brakes applied and reduces wear and tear on car brake components and wheels. The expanded use of dynamic brakes was initially a fuel-saving practice, as evidenced in the early engineer-assist systems for dynamic braking that focused on saving costs. However, because dynamic brakes concentrate braking power in the locomotives as opposed to the whole train as with train air brakes, it is not clear that dynamic braking should be the preferred or primary method of train control in all situations. In 2023, NTSB required FRA to ensure that railways have proper procedures in place to ensure that train speed can be maintained by automatic brakes alone in case DP is unavailable or suddenly lost en route.57 The committee found no guidance on when or if using train air brakes should be prioritized over using dynamic brakes and how train length affects this decision.
FRA Studies of Air Brake Systems in Long Trains
FRA conducted a series of tests between 2020 and 2024 on air brakes on very long trains. The final technical reports for Phases II–IV were publicly released in May 2024.58 Phase II’s rack tests simulated the air brakes on trains of up to 200 cars.59 Phase III’s tests were conducted on a stationary train of 200 cars.60 Phase IV’s tests took place on a moving train in a DP
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55 Harvey, W.T. 2023. High Iron & Big Boys: The Life and Times of a Union Pacific Steam Engineer. South Platte Press.
56 Today engineers are taught to rely more on dynamic brakes to keep trains bunched to control in-train forces and to save fuel by not pulling and braking simultaneously.
57 NTSB Safety Recommendation Report on Train Emergency Brake Communication, September 2019, https://www.ntsb.gov/investigations/AccidentReports/Reports/RSR1902.pdf.
58 Representatives of FRA briefed the committee on the progress of these very long train studies in March 2023 and March 2024.
59 FRA. 2024. “Very Long Trains—Phase II: Rack Tests.” DOT/FRA/ORD-24/18. May. https://railroads.dot.gov/sites/fra.dot.gov/files/2024-05/VLT%20Phase%20II%20Report.pdf.
60 FRA. 2024. “Very Long Trains—Phase III: Stationary Train Tests.” DOT/FRA/ORD-24/19. May. https://railroads.dot.gov/sites/fra.dot.gov/files/2024-05/VLT%20Phase%20III%20Report.pdf.
BOX 3-1
FRA’s Key Findings from Its Very Long Train Studies of Air Brake Systems
The following are FRA’s key findings from its series of studies conducted between July 2020 and May 2024 on the air brakes of very long trains:
- Phase II of testing, using only head-end power, found that the likelihood of unintended brake releases was higher with longer trains and that increased train lengths led to slightly slower brake response times.
- Phase III of testing found that distributed power train configurations achieve better braking capability than only head-end power on long train operations.
- Phase IV of testing found that when long trains climbed a grade, certain sections of the train consist experienced elevated buff forces and coupler forces, which can influence how a train behaves and impact the safe handling of trains with distributed power.
- Phase IV of testing concluded that further testing is needed to identify potential safety gaps when operating long trains in nonideal operating conditions.
- The research team also made clear in Phase IV, the final phase of testing, that additional research, testing, and analysis is recommended to provide a better understanding of how long trains impact the durability of rolling stock mechanical components.
SOURCE: FRA. 2024. “FRA Rigorously Examines Safety and Quality of Life Implications of Long Trains.” https://railroads.dot.gov/about-fra/communications/newsroom/press-releases/fra-rigorously-examines-safety-and-quality-life-0.
configuration with 228 cars as it traveled 1,300 miles over plains, mountains, and rolling hills.61 FRA’s key findings are summarized in Box 3-1.
A key finding from the rack tests (head-end power only) was that air brake recharge time for a 200-car train took three times longer than a 100-car train,62 while the static rail tests further confirmed that air brake propagation time increases with train/car length.63
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61 FRA. 2024. “Very Long Trains—Phase IV: Moving Train Tests.” DOT/FRA/ORD-24/20. May. https://railroads.dot.gov/sites/fra.dot.gov/files/2024-05/VLT%20Phase%20IV%20Report.pdf.
62 FRA. 2024. “Very Long Trains—Phase II: Rack Tests.” DOT/FRA/ORD-24/18. May. https://railroads.dot.gov/sites/fra.dot.gov/files/2024-05/VLT%20Phase%20II%20Report.pdf.
63 FRA. 2024. “Very Long Trains—Phase III: Stationary Train Tests.” DOT/FRA/ORD-24/19. May. https://railroads.dot.gov/sites/fra.dot.gov/files/2024-05/VLT%20Phase%20III%20Report.pdf.
Even with the expansion of test elements during the fourth stage, FRA officials indicated that “no unusual events” occurred during the monitored trip.64 Peak coupler forces measured were about ±400 kips;65 while trains do routinely experience comparable levels, especially during periods of elevation change where climbing front cars push against trailing accelerating downslope cars, in-train forces have occasionally been the primary cause of derailments with amounts as low as ±135 kips.66 The reported coupler forces were significant enough for FRA to highlight as a core goal of its next phase of research to “more thoroughly investigate factors contributing to the elevated coupler forces observed during the tests.”67
This first moving train test occurred with a uniform unit makeup and under ideal weather conditions (although the route did traverse mountainous terrain). However, FRA aims to conduct additional monitored runs to test long train brake performance under more complex situations.68 Such tests could prove instrumental in updating industry guidelines for train makeup for longer manifest trains with DP locomotives.
Electronically Controlled Pneumatic Brakes
NTSB has recommended that certain freight trains be equipped with ECP brakes.69 In ECP brakes, brake applications are triggered via an electronic signal sent through wires that produce a simultaneous application of air brakes throughout the entire train. Compared to conventional air brakes that gradually traverse the train, the simultaneous application of ECP brakes could be advantageous for longer trains. In addition, because the brake application signal does not require reducing air pressure in the trainline, a full release or a partial release of train air brakes would not subsequently require the train air brake system to be recharged. ECP brakes’
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64 FRA presentation to committee, March 2024.
65 A kip is an American unit of measurement equal to 1,000 pound-force. FRA. 2024. “Very Long Trains—Phase IV: Moving Train Tests.” DOT/FRA/ORD-24/20. May. https://railroads.dot.gov/sites/fra.dot.gov/files/2024-05/VLT%20Phase%20IV%20Report.pdf.
66 Government of Canada National Research Council. 2024. “Industry Review of Long Train Operation and In-Train Force Limit—NRC Publications Archive.” May 3. https://nrc-publications.canada.ca/eng/view/object/?id=bcc92202-14a8-476b-9500-5a384c4ff003.
67 FRA. 2024. “Very Long Trains—Phase IV: Moving Train Tests.” DOT/FRA/ORD-24/20. May. https://railroads.dot.gov/sites/fra.dot.gov/files/2024-05/VLT%20Phase%20IV%20Report.pdf.
68 Ibid.
69 For an overview of NTSB’s recommendations on ECP brakes and the railroads’ reactions, refer to Chapman, T.B., and NTSB. 2022. “Testimony Before the Railroads, Pipelines, and Hazardous Materials Subcommittee Committee on Transportation and Infrastructure on Examining Freight Rail Safety.” June 14. https://www.ntsb.gov/news/Testimony/Pages/Chapman-20220614.aspx.
potential advantages include improved safety, reduced stopping distances, and less wear on train wheels and brake shoes.70 The main limitations for current freight train air brakes are that time is required for braking commands to propagate along the length of a train, and braking action cannot be reduced without releasing the air brakes entirely. Both of these limitations could be eliminated with the use of ECP brakes that are more flexible and faster acting; however, ECP brake use is not supported by Class I railroads due to reliability problems in earlier tests and the cost of equipping the entire fleet of freight cars for ECP operation. Finally, because ECP brakes are incompatible with conventional air brakes (without extensive technical modifications), other disadvantages include time and operational challenges of outfitting the entire North American interchange rail car fleet and locomotives, the cost of maintaining the new system, and the ongoing time and cost of recoupling wires after cars are separated for switching (in addition to reconnecting the train air line).71
Although the industry has previously tested ECP brake systems, no freight railroad currently uses ECP brakes in the United States. In addition, there is currently no consensus on next steps for widespread ECP brake adoption. The Association of American Railroads (AAR) contends that ECP brakes suffer from an unacceptable failure rate while offering inconsequential safety improvements.72 Two Class I railroads that tested ECP brakes on coal trains found the technology too unreliable to be adopted.73 At the Railroad Safety Advisory Committee (RSAC) meeting held in March 2023, FRA created a working group to “consider and identify potential methods of modernizing train brake equipment and brake-related processes and procedures to improve train braking effectiveness, including consideration of the use of locomotive DP or ECP brake systems, or a combination of those systems.”74 It should be noted that both New York Air Brake and Wabtec, the two manufacturers of ECP brake systems available in North America, indicated to the committee that they have continued to do research and development to improve ECP braking system reliability and lower ECP braking system costs.75
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70 National Academies of Sciences, Engineering, and Medicine. 2017. A Review of the Department of Transportation Plan for Analyzing and Testing Electronically Controlled Pneumatic Brakes. Washington, DC: The National Academies Press. https://doi.org/10.17226/24698.
71 FRA. n.d. “Accelerating Implementation of ECP Emulator Technology.” https://railroads.dot.gov/elibrary/accelerating-implementation-ecp-emulator-technology (accessed May 3, 2024).
72 AAR. 2023. “Electronically Controlled Pneumatic (ECP) Brakes Fact Sheet.” March. https://www.aar.org/wp-content/uploads/2023/02/AAR-ECP-Brakes-Fact-Sheet.pdf.
73 BNSF presentation to committee, April 2023; Norfolk Southern presentation to committee, January 2023.
74 RSAC Meeting, March 2023. https://rsac.fra.dot.gov/meetings?id=63.
75 New York Air Brake and Wabtec presentations to committee, May 2023.
Despite the railroads’ concerns about the technology, ECP brake systems could someday provide another layer of safety for two reasons. First, train air brakes can be partially released without releasing brakes entirely. Second, accidents resulting from air brakes bleeding off could be prevented as trainlines can be charged continuously.
Positive Train Control
The use of PTC was mandated by Congress as part of the 2008 Rail Safety Improvement Act and all affected railroads were in compliance by December 29, 2020.76 PTC systems are backup systems that use train monitoring and control technologies to automatically stop a train if unsafe conditions (such as excessive speed) are detected and thereby prevent train collisions, derailments, and certain train switching movements.77 While challenges exist with the use of PTC,78 including the addition of another information screen that needs to be monitored by the train crew, the committee did not find examples showing that the use of PTC increased problems with long train derailments. Regarding safety and community impacts, one railroad uses PTC to notify dispatchers when trains are stopped on road crossings for more than 10 minutes.79 However, overall train length is currently represented in PTC systems as an estimate based on the GPS coordinates of the lead locomotive plus the number of cars listed in the railway’s manifest. Increased certainty with regard to the location of the end of a train could assist with research on a number of safety issues, such as the duration of time spent in grade crossings.80
CREW COMMUNICATIONS TECHNOLOGY
Maintaining effective crew communication is a crucial aspect of a safely operating train, and federal regulations require that all occupied locomotives have a working radio along with a backup wireless system.81 Roadway and onboard crew communicate with central dispatchers and supervisors
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76 FRA. 2023. “Positive Train Control (PTC).” October 10. https://railroads.dot.gov/research-development/program-areas/train-control/ptc/positive-train-control-ptc.
77 AAR. n.d. “Freight Rail & Positive Train Control.” https://www.aar.org/issue/positive-train-control (accessed May 3, 2024).
78 FRA. 2021. “Positive Train Control Interface Design Issue with Locomotive and Cab Car Braking Systems.” Federal Register 86:49410–49411. Washington, DC: Government Printing Office.
79 Union Pacific presentation to committee, March 2023.
80 FRA. n.d. “Positive Train Location: Final Report.” DOT/FRA/ORD-18/17. June 20, 2018.
81 “Railroad Communications.” 49 C.F.R. Part 220. https://www.ecfr.gov/current/title-49/part-220 (accessed May 3, 2024).
to navigate track occupation, coordinate maintenance schedules, and report problems (both onboard and trackside).82 Onboard crews also need an unconstrained ability to coordinate with each other in order to maintain optimal train operations. These communications, which were originally made using hand signals, now occur using radios. These two-way, short-range, very high frequency radios have a limited range based on “line of sight,” which naturally creates more problems for longer trains, especially those moving through rugged terrain. A crew member who is walking the train looking for broken air hoses, derailments, sticking brakes, and hot bearings or is walking back to cut the train into multiple sections to clear road crossings will be equipped with a handheld radio.83 On long trains, the power limits of the individual radio systems may detrimentally affect communications. Radios in the cab of the locomotive typically have more power (e.g., 35 W) and range than the handheld radios commonly used by conductors (e.g., 5 W). As a result, engineers can transmit to conductors, but not always vice versa. The primary train dispatcher’s union believes long trains have also increased the difficulty of switching operations and inspections, because radio instructions with downrange crew often must be relayed through the locomotive. Besides creating problems with communications, this situation can create a hazard for crews riding equipment to make a coupling, fix a broken knuckle, or switch an industry. Maintaining communications through line of sight may become more hazardous when crew members are riding moving equipment and must use one hand to hold the radio handset aloft (called the statue of liberty position).84
Current regulations require that trains have one working radio in the controlling locomotive and a backup radio somewhere.85 Railroads are currently experimenting with roving conductors or utility people who can drive to where they are needed quicker than if they had to walk from the front of the train.86 It should be noted that, when communication is lost between crew members, these rules require the train crew to stop further movements of all rolling railroad equipment until communication is reestablished, which can often result in lengthy delays.
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82 “Communication and Coordination Demands of Railroad Roadway Worker Activities and Implications for New Technology.” FRA Office of Research and Development, November 2007. https://railroads.dot.gov/sites/fra.dot.gov/files/fra_net/389/ord0728.pdf.
83 GAO (U.S. Government Accountability Office). 2023. “Rail Safety: Freight Trains Are Getting Longer, and Additional Information Is Needed to Assess Their Impact.” June 1. https://www.gao.gov/products/gao-19-443.
84 BLE&T presentation to committee, January 2023.
85 “Railroad Communications.” 2024. 49 C.F.R. Subtitle B, Chapter II, Part 220. Washington, DC: Federal Railroad Administration, U.S. Department of Transportation. https://www.ecfr.gov/current/title-49/subtitle-B/chapter-II/part-220.
86 BLE&T presentation to committee, January 2023.
Although technology has improved communication overall between locomotives, communication among crew members potentially becomes more difficult as train size increases. However, there are currently limited data to fully analyze the risk.87 A focus group–based study of railroad stakeholders found that the perception of long train communication challenges varied among FRA staff, representatives of labor unions, and railroad managers.88 Both FRA staff and labor representatives agreed that the loss of radio communication on long trains is a safety issue, but only the latter directly asserted that long trains consistently exceed radio communication limits.89 While there was no consensus among FRA staff over the extent to which long trains experience radio problems in comparison to shorter trains, FRA representatives agreed that train length is one of several variables that can negatively impact communications.90 Furthermore, the identified communication issues haves been impacted by the lack of bandwidth available from FCC.91
Representatives from the railroads countered concerns about disrupted radio communication by stating that communication problems in the field are a longstanding issue but long trains have operated without incident over the past 80 years.92 In addition, loss of radio communications should not result in an accident as long as railroad staff are following railroad communication rules.93
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87 FRA. 2022. “Stakeholder Perceptions of Longer Trains.” DOT/FRA/ORD-22/43. December. https://railroads.dot.gov/elibrary/stakeholder-perceptions-longer-trains.
88 Ibid.
89 SMART and BLE-T presentations to committee, January 19, 2023.
90 FRA. 2022. “Stakeholder Perceptions of Longer Trains.” DOT/FRA/ORD-22/43. December. https://railroads.dot.gov/elibrary/stakeholder-perceptions-longer-trains.
91 Willauer interview with Bruce Marcheschi, December 14, 2023.
92 AAR presentation to committee, January 20, 2023.
93 Both widely used books of rules require engineers to stop trains at half the distance last requested if radio communications are interrupted.
