How Do Railroads Keep Track of Cars?

How do railroads keep track of cars? To keep track of cars, railroads utilize various technological methods including RFID technology, AEI tag readers, and virtual geographic zones. These technologies have helped to revolutionize the efficiency of daily railroad operations. 


Since the dawn of commercial rail travel, keeping an accurate account of the goods being shipped has proved to be a tedious task. In North America, many railcars are leased by railroads via leasing companies, therefore, rail car owners oftentimes want exact locations of their stock. With the advent of radio frequency identification (RFID), tracking railcars has become easier for both the railroad and the customer. Prior to this groundbreaking technology, railroad workers would have to view slow motion film of trains departing the rail yard, taking note of each car’s reporting mark and running number to determine on which train the railcars were leaving the yard.

In the 1960s, North American railroads began looking for an alternative to the time and resource consuming practices that were currently in use. In the late seventies, various American railroads began experimenting with railcar tracking technology called Automatic Car Identification (ACI). The ACI system operated via optical technology, where the trackside transponders read a colored bar code on the side of the rolling stock. This system worked effectively, however, not without its drawbacks, as the transponders failed to read the bar codes when they accumulated dirt. This system remained in place until the late seventies.

After ACI technology, various companies such as General Electric, devised their own form of railcar tracking systems utilizing Radio Frequency Identification. One of the most prominent, the RailTrak system, developed by General Electric, operated by placing an interrogator in the track gauge, while a RFID tag was mounted underneath the railcar. However, the latest emerging technology, called Automatic Equipment Identification (AEI), has taken the industry into a new dimension of efficiency.

Ed Gately

Automatic Equipment Identification (AEI)

Automatic Equipment Identification (AEI) had revolutionized the railcar tracking process. This technology is operated through trackside wayside detectors, which read transponders on the side of the railcars. Once the wayside detector reads the transponder on the side of the car, the information is sent to the railroad’s central computer, which displays the car’s location. Although many believe the technology is dated, railroads continue to maximize the capabilities of the system and other forms of wayside equipment to track their trains.

One approach is the linking between the wayside devices and GPS technology to track trains with information such as arrival time into a terminal or classification yard. Many railroads have fitted their locomotives with GPS to track their location in real-time. Thus, the technology is used in unison with the AEI system by combining AEI information with the timestamp on GPS equipped locomotives, thus, recording more accurate readings on train location.

In addition to tracking railcar location, railroads also use wayside technology to detect rolling stock defects. Defects detected by wayside devices include hot wheels, axles, and bearings, (also called a hotbox), which alerts the engineer via radio communications. This reduces the number of staff needed to inspect the railcars, and allows trains to operate on time and with increased efficiency.

Although the AEI system is an effective way to keep tabs on rolling stock, it is not cost effective to install a reader at every track in a major classification yard. Therefore, various whereabouts are oftentimes taken manually, for example, if a railcar is moving to an adjacent track, the move would be manually recorded. However effective, keeping track of rolling stock manually is prone to error, thus, an AEI tag reader placed on the outskirts of the yard would detect the error, and create a automated waybill detailing the correct destination of the car.

Virtual Geographical Zones

An emerging technology utilized by various railroads, such as Norfolk Southern and CSX, are the implementation of a “geo-fence”, or “virtual zone”. This system works by assembling a virtual perimeter around various stretches of track, or a large classification yard, therefore, the locomotive and its subsequent cars in the relative consist are accounted for via the timestamp on the locomotive’s GPS. With these virtual perimeters in place, when the train is introduced to the “geo-fence”, its GPS relative to the time the locomotive entered the geo-fence is arranged, thus, the train’s location is decided based on when it enters and exits the virtual perimeter. These types of geo-fences are called passive geo-fences, as the locomotives must be equipped with GPS systems, thus, the geo-fence will only be able to locate trains if the GPS technology is engaged.

The desired perimeter is prepared by the railroad, which sets the desired area of the geo-fence. When a GPS equipped locomotive enters and departs the the virtual perimeter, the railroad is notified. The railroad knows that the cars on the train are allocated to the GPS equipped locomotive by its road number, thus, the railroad knows the location of each railcar when it enters or exits a virtual zone. This technology even allows railroads to track cars in parts of their system where AEI is not employed, if the locomotive is GPS equipped. This allows the railroad to attain a more accurate account on where railcars are located, even when they are on a customer’s freight siding being unloaded or waiting to be picked up. Although GPS systems are usually only installed in locomotives, a select number of railcars will receive the technology, however, only if the car is carrying extremely hazardous material, however, this practice is not commonplace.

With real-time information traveling faster than ever before in the modern era, railroads are continually searching for improved ways of tracking railcars. Some rail companies are researching to use of motes, which are small devices with a powerful computer chip, capable of communicating with other motes in the surrounding area. The motes would be attached to the side of a railcar, and would be capable of realizing car status in real-time. These devices could also monitor the mechanical status of the car, and even detect defects, such as radiation from a tanker car.

With the ever expanding world of communications, and the availability of real time information in the modern age. Railroads continually search for enhancements and even replacements to the current system, as AEI was introduced in the eighties, and many in the industry believe the technology is outdated.

Ben Sutton

Tracking Railcars in Britain

Developed by the Southern Pacific Railway operating on the west coast of the United States, the British Total Operations Processing Systems (TOPS) system is employed to track railcars and locomotives in Britain. Originally purchased by British Rail in the 1970’s, the computerized TOPS system is designed to handle tracking the location of cars, maintenance status, and destination, updated by computers at each depot or maintenance facility, as this data was previously handled via paperwork.

In the height of advancement, British Rail began looking for a way to improve efficiency, and decided to implement the TOPS systems after a presentation by an IBM representative from the U.S. However, locomotives had to be renumbered, as the TOPS system was not compatible with the current arrangement. Previously under British Rail, diesels were denoted with a prefix”D” before its running number, and electric locomotives with a prefix “E”, however, this system lacked sequential numbers, thus, every locomotive in the country had to be renumbered. The locomotives were hereby divided into classes, with three digit running numbers. Below is an report that could be assembled on a TOPS computer, courtesy of the South Devon Railway Newsletter:

K383400 0010 2837 22/10/86 U483 ON N199 BY KO
LOCO 25901
LOCO 25908
37015 OVER&WHAR 1520 025 00071212
65700 BESCOTYDNRP1707 EST 1709 EST 025 000
74260 READINGWJDETAIL2007 EST025 000

This system revolutionized the way rolling stock was tracked, as information about location were stored in computers instead of paperwork, which was oftentimes, difficult to keep track of. However, many believe that the TOPS system is outdated, especially after privatization in the mid-nineties. Additionally, the system utilizes its own programming language, which proves difficult when familiarizing developers with the system. Although outdated, the benefits of the system have far outweighed its flaws.


Lifelong Rail Enthusiast and Owner of Worldwide Rails

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