In This Issue
Transportation Infrastructure
June 1, 2008 Volume 38 Issue 2
Transportation Infrastructure issue of The Bridge, Volume 38, Number 2, Summer 2008

The Freight Railroad Renaissance

Sunday, June 1, 2008

Author: John M. Samuels

America’s freight railroad system is the envy of the world.

When I mention freight railroads, most people think of steam engines and passenger trains rather than freight trains, and considering Americans’ love for passenger trains over the years, this is not surprising. Since the advent of the interstate highway system in the 1950s, freight railroads have had a difficult time competing with highway trucks. In fact, by 1980 many freight railroads were on the verge of bankruptcy. In response to this dire situation, Congress passed the Staggers Rail Act of 1980, which deregulated the railroads and allowed them to compete freely in the marketplace.

Changes in the market share of U.S. railroads from 1980 to 2005
FIGURE 1 - Changes in the market share of U.S. railroads from 1980 to 2005. Note: Pipeline does not include natural gas. Source: DOT, 2007.

As freight railroads learned to compete, they emerged from those difficult times to become an increasingly vital part of America’s transportation infrastructure (Figure 1). To compete effectively with other transportation modes, railroads knew they had to not only reduce their costs but also improve their service reliability (Figure 2). With time, as rail freight service became more reliable, the volume of freight transferred from highway trucks and containers back to freight railroads increased dramatically, based on cooperative agreements between trucking companies and railroads.

Improvements in productivity, volume, revenue, and cost reduction since 1980.
FIGURE 2 - Improvements in productivity, volume, revenue, and cost reduction since 1980. Source: AAR, 2008.

The general size of the North American freight railroad network is shown in Figure 3. The industry consists primarily of seven major railroads, called Class 1 railroads, and numerous smaller regional and short-line railroads. Freight railroads in the United States operate as a single system based on universally accepted interchange rules maintained by the Association of American Railroads (AAR) in Washington, D.C. Tracking information on car flow and interchange data are collected by Railinc, a wholly owned subsidiary of AAR.

Map showing the extent of the freight railroad track network in North America.
FIGURE 3 - Map showing the extent of the freight railroad track network in North America. Source: Reprinted with permission of AAR.

The successful operation of individual, for-profit, private companies working together in an integrated system has made America’s freight railroads the envy of the world. Until the 1990s, freight railroads in most other countries were government owned. Since then, however, following the U.S. model, many countries are privatizing their freight rail operations, driven largely by the realization that railroads must be part of the “green” solution to the growing problems associated with global warming and petroleum dependency. From 1980 to 2006, railroad fuel efficiency in the United States improved by 80 percent. Today railroads are three or more times as fuel efficient as highway trucks, and locomotives emit far fewer greenhouse gases than trucks per ton-mile of freight moved. Another reason for the “greening” of railroads is that a typical freight train can carry several hundred truckloads of freight, which helps reduce both highway congestion and wear and tear on highway infrastructure.

Thus the picture of freight railroading today is very different from the picture in 1980. Freight railroads today are poised for a renaissance, and creative applications of science and engineering will ensure that railroads take their rightful place as a strategic part of America’s future.

The Digital Railroad of the Future
Efforts are currently under way to define the railroads of the future. Numerous reports have been issued by AAR and other government agencies involved in planning the U.S. transportation infrastructure, such as the U.S. Department of Transportation and the Federal Railway Administration. In addition, the American Association of State Highway and Transportation Officials (AASHTO) issued a comprehensive report in January 2001 entitled Transportation Investments in America: Freight Railroad Bottom Line Report, reiterating the critical need for a strong American freight railroad infrastructure. In September 2007, AAR issued National Rail Freight Infrastructure Capacity and Investment Study, in which the authors quantified the need for added rail capacity to handle projected traffic levels for 2035.

All of these reports also identified a need for railroads to continue to improve safety, productivity, and service reliability through the creation of a digital railroad communications infrastructure that would enable railroads to expand the use of computerized control systems related to almost every aspect of railroad operations. Some of the most important of these are described below.

Schematic drawing of the critical wheel/rail interface.
FIGURE 4 - Schematic drawing of the critical wheel/rail interface.

Digital Railcar-Inspection Devices
Wheel-Impact Load Detectors
Railroads deploy wayside detector systems along the railroad right-of-way to assess the dynamic health of railroad cars in transit. These detectors measure the forces created at the wheel/rail interface (Figure 4), which should be kept at a minimum to maximize the useful life of the track structure. Today, approximately 107 digital wheel-impact load detectors (WILDS) are deployed on railroad mainline tracks.

As a train passes over the detector at track speed, wheel loads are measured around the circumference of each wheel, and nominal and impact loads are recorded. Wheels that normally have vertical loads of 36,000 pounds per wheel for a loaded railcar can create excessive impact loads, up to approximately 160,000 pounds per wheel, if the wheel running surface is damaged. Wheel-impact data from WILDS are digitally transmitted to InteRRIS, an industry-wide database maintained by Railinc. Railcars with defective wheels are tagged in the computer system and routed to car repair shops.

Truck-Performance Detectors
In-track sensors used in WILDS are placed on curves to measure the lateral forces exerted by railcars as they travel around the curve. These detectors, known as truck-performance detectors (TPDs), measure both vertical and lateral forces exerted on the rail to assess the railcar’s ability to negotiate the curve. Data from these detectors are also sent to InteRRIS, and railcars with poor steering are routed to car repair shops before they cause excessive damage to tracks. TPDs are used to measure the stresses exerted by all 1.8 million railcars that transit America. Data are kept for the life of the railcar, so railroads can monitor railcars over their useful lives and send cars that could potentially cause train derailments to repair shops.

Hot-Bearing Detectors
A third type of wayside detector monitors roller bearings on railcar wheels to determine if the bearings are near failure. Hot-bearing detectors (HBDs) use infrared cameras to measure the temperature of roller bearings to ensure that it is within the normal operating range. If an HBD finds a bearing with too high a temperature, the train is stopped, and the bearing is inspected.

Track-side acoustical detector (TAD).
FIGURE 5 - Track-side acoustical detector (TAD). Source: Reprinted with permission of Norfolk Southern.

Trackside Acoustical Detectors
Recently deployed trackside acoustical detectors (TADs) measure the sounds made by bearings as they pass by the detector at track speed and use digital pattern recognition to identify bearings that are near the end of their useful lives. A TAD detector (Figure 5) usually identifies a bearing long before it is about to fail, so the railcar can continue to its destination and then stop for repairs at the next convenient point in its transit.

Digital Train-Inspection Devices
As part of the Advanced Transportation Safety Initiative (ATSI), the railroad industry research facility in Pueblo, Colorado, known as the Transportation Technology Center Inc. (TTCI), is developing wayside inspection units that use laser cameras and/or digital machine vision pattern-recognition systems. FRA, industry suppliers, AAR member railroads, and TTCI researchers are working hand-in-hand to solve the industry’s most challenging safety problems. Systems positioned on the railroad right-of-way can conduct a complete safety inspection of railcars before they leave the terminal. Thus cars found to have problems can be cut out of the train. This capability will dramatically reduce the probability of in-transit failures.

Digital Track-Inspection Devices
Laser-Acoustic Rail-Flaw Inspection
Railroads have historically used ultrasonic inspection systems to look for internal defects in steel rails. Inspections are carried out by on-track inspection vehicles that move down the track at about 3 miles per hour (mph). Fatigue defects in rail steels develop over time from stress transmitted at the wheel/rail interface. These defects usually grow slowly as a result of repeated stress cycles until they reach a critical size, at which point the rail must be removed.

Current ultrasonic rail-inspection techniques cannot detect defects in the base of a rail, but a new higher powered laser-acoustic system will be able to inspect approximately 98 percent of the rail cross section. With this system, the inspections truck can travel up to about 18 mph along the right-of-way, while computers aboard the car record digitized data from the acoustic signals and process the data into a GIS database. This system will make it significantly easier to find rail flaws before they become a safety concern.

Track-geometry car (TGC).
FIGURE 6 - Track-geometry car (TGC). Source: Reprinted with permission of Norfolk Southern.

Automated Digital Track-Geometry Cars

All Class 1 railroads in America own one or more track-geometry cars (TGCs). A TGC (Figure 6) is equipped with multiple computer systems that measure the quality of the railroad track structure as the TGC rides over it at speeds of up to 70 mph. Lasers and camera systems record both the quality of track geometry (e.g., gauge, cross-level, and vertical bounce) and wear dimensions. These real-time data-acquisition systems feed the latest track-quality parameters into predictive models that can be used to plan maintenance programs. Real-time track measurements are compared to FRA track standards, and variations are immediately tagged for corrective action.

Gauge-restraint measuring car (GRMC).
FIGURE 7 - Gauge-restraint measuring car (GRMC). The self-contained motorized railcar is on the left; a high-rail inspection vehicle is on the right. Source: Reprinted with permission of Norfolk Southern.

Another variation of the TGC, which is being used more and more frequently, is the gauge-restraint measuring system (GRMS). This car is similar to a TGC but has a split-axle system in the middle of the car (Figure 7). When activated, the split-axle system puts a lateral load on the inside gauge faces of the rail simulating the lateral forces exerted by a passing train and testing the ability of the track (i.e., the fastening system that holds the rail to the railroad ties) to withstand the load. GRMS vehicles are usually run at about 30 mph to test lateral track strength. Data acquired from GRMS cars is also fed into a GIS database and used for maintenance planning purposes to ensure that weak spots are repaired.

Digital Train-Control Systems
Positive Train-Control Systems
Today the majority of high-tonnage mainline track is equipped with failsafe signal-control systems that work very much like traffic signals on highways. Although there is a wide variety of signal systems, most of them work on the principle that when a locomotive crew receives signal-light indications either from fixed signals on the right-of-way or in the locomotive cab, the crew will obey those signals. Crews also have analog voice radio communications with train dispatchers who control the movement of trains. Dispatchers give train crews permission to proceed, either by changing the signal indications along the right-of-way or by issuing authority verbally (a track warrant) via analog voice radio.

These systems, which have been in place since the early 1900s, have been refined and improved technologically over the past 60 years. However, all of them require a great deal of human voice communication and rely on employees to follow operating rules and signal indications properly. Converting train-control systems to digital communications systems will create endless possibilities for computer-based interventions that can prevent human error.

General structure of a positive train-control (PTC) system.
FIGURE 8 - General structure of a positive train-control (PTC) system. Source: Reprinted with permission of AAR.

The generic conceptual structure of the digital systems, called positive train-control (PTC) systems, is shown in Figure 8. Digital authority to proceed is sent to a crew from a central office computer system that tracks all train movements and checks for conflicts. The main office computer also controls all wayside devices, such as switches at the dispatchers’ command, but only after all routes have been checked for conflicts. By digitally downloading instructions, PTC systems can fully automate the train-control system.

The component of the system aboard the locomotive, the locomotive-control unit (LCU), consists of computers with software functions that monitor the crew’s implementation of movement authorities. An LCU can stop the train if conditions are unsafe. Once PTC systems are installed, the possibilities for improvement are endless. Several systems currently under development are being tested on several railroads and at the TTCI research facility. As PTC systems become cost effective, they will be widely implemented in the next 15 years. Real-Time Onboard Train-Performance Simulators
With PTC systems aboard, the automation of real-time train operations will become feasible. PTC systems will be able to optimize acceleration and/or braking to minimize fuel consumption and train-handling forces. To assist crews, these systems can recommend train-handling instructions based on tonnage, track grade and curvature characteristics, allowable speed, and train-dynamic performance. Simulators can optimize operations by calculating several hundred train-handling alternatives per second and forecasting train velocity several miles in advance.


A typical coaching screen for real-time train-performance simulation.

A typical coaching screen for real-time train-performance simulation. Source: Reprinted with permission of Norfolk Southern.

Figure 9 shows a typical coaching screen on a locomotive for a PTC system (right). This screen is from a system called LEADER, manufactured by New York Airbrake Corporation, which is currently being installed on several railroads around the world. The locomotive engineer is shown train position, track grade and curvature, in-train tension and compression forces, and train speed and acceleration. The number in the small blocks at each track milepost location is the predicted train speed at that location, provided that throttle and brake conditions remain unchanged. In the lower right-hand block on the screen, the locomotive engineer is given suggestions for changing throttle or braking conditions.

Electronically Controlled Pneumatic Braking Systems
Digital applications can be extended to current braking systems, which have been used for more than 100 years. Designed as failsafe systems, brakes are applied automatically if there is a loss of air pressure in the brake pipe that runs the length of the train. Compressors on the locomotive pump air under pressure through the brake pipe, and airbrake valves on each railcar respond to changes in air pressure in the brake pipe. Currently, it can take several minutes for the air pressure drop to travel from the front of the train to the rear.

With an electronically controlled pneumatic (ECP) braking system, the brakes on all cars are activated at the same time by electrically activated valves, providing a much smoother braking action that can stop a train in approximately half the distance it takes for a conventional braking system. With ECP, a wire extends power to each car in the train. The wire also has circuits for digital communications from each car to the locomotive. Thus it will be feasible to power a monitoring system of the performance of each railcar in the train in real time. Railcars in the future may have low-power, wireless monitoring systems that report unsafe conditions to the crew even as the train is moving.

As the descriptions of digital applications described in this article show, the railroad renaissance is alive and well. Railroads today offer the safest, most energy-efficient mode of handling long-haul freight, and operations will only get better in the future. Conversion of railroad communications systems from an analog infrastructure to a digital infrastructure will facilitate the rapid deployment of computer-based applications that will accelerate improvements in safety, productivity, and reliability. The benefits of the digital railroad to the future of the U.S. transportation infrastructure will rival the benefits of railroads in the 1800s to the western United States. It will be a true renaissance.

AAR (Association of American Railroads). 2007. National Rail Freight Infrastructure Capacity and Investment Study. Washington, D.C.: AAR.
AAR. 2008. Overview of America’s Freight Railroads. Washington, D.C.: AAR.
AASHTO (American Association of State Highway and Transportation Officials). 2001. Transportation Investments in America: Freight Railroad Bottom Line Report. Washington, D.C.: AASHTO.
DOT (U.S. Department of Transportation). 2007. National Transportation Statistics 2007. Available online at statistics/excel/table_01_46b.xls.



About the Author:John M. Samuels is president of Revenue Variable Engineering LLC and an NAE member.