Part 1 of this article discussed the concept and basic implementation of the end of train (EOT) device. This part explores the EOT and its larger “ecosystem” in more detail.
First, a bit of history
While the first caboose replacement was a simple flashing rear-end device (FRED), first used by the Florida East Coast Railroad in 1969, it was soon superseded by a more advanced EOT device design primarily due to the impact of the EOT devices. By the mid-1980s, new labor agreements and changes in state laws defining minimum crew sizes allowed the railroads to reduce the crew per train to just the engineer (driver) and conductor, who sits up from in the cab next to the engineer. Many states and union rules initially required a minimum crew of five, which then became four, then three, and then two). Canada’s train rules and laws changed at around the same time. Again, Reference 1 is a good discussion of how railroads made the transition away from cabooses to EOT devices.
EOT device functions advance
The EOT device fits over the rear coupler of the last car on the train or attaches to a grab iron, hook, or frame member of the car. Powered by an internal battery, the device sends a periodic signal to the locomotive indicating the brake pressure at the rear of the train, whether or not the last car of the train is moving, and in which direction. EOT devices are also equipped with a flashing red light, activated at night by a sensor, which serves as the train’s rear marker.
The first EOT devices used disposable primary batteries, but rechargeable secondary batteries were soon are also used. EOT devices were also available, which could also be powered by a small turbine-powered electrical generator using air pressure from the brake line (Reference 7). This did not eliminate the need for batteries, which are still needed when there is no brake pressure, so EOT units can provide location-based “asset tracking” for months and years despite being in sleep mode. Further advances in low-power circuitry and battery technology allow appropriate functions of the EOT devices to operate for months on a single battery, despite all the new capabilities and features.
The mechanical-design considerations for an EOT device – independent of its functions – are challenging. “Reliability” takes on many meanings in this application, as the railroad is a very harsh environment in so many ways. First, there are temperature and water-related extremes which affect the EOT-device components, including battery and displays, from its first minute of operation. There are many photos of cars, couplers, and EOT devices covered with inches of ice and yet they must still work (see the exciting movie “Runaway Train”, Reference 11). For enhanced ruggedness, the antenna is often located inside the tough, engineered-plastic enclosure.
Then there is the constant vibration generated during travel, and also the repeated shocks when coupling or uncoupling, or being bumped by another car during normal activities in the yard or at a siding, Dislodged gravel, track ballast, and stones will pelt it at high speed. There is also malicious vandalism and general abuse. In short, a reliable EOT must be made rugged in ways that even “ruggedized” electronics alone cannot come close to providing.
Even the issue of how to attach the EOT device is not trivial. Some EOT devices attach to the body of that last car – there are various grab irons and frame pieces to use – but most attach to the exposed coupler (Figure 1). Regardless of the locations, it has to be easy to attach and remove yet also be secure, as there are serious consequences if it falls off along the route. The train must go to reduced-operation mode, and it’s a genuine hazard to other trains (and who can say on which track it eventually lands?). Note that the EOT device has no electrical connection to the train, which eliminates one headache. There is only the connection to the brake-pressure line.
Today’s train: isolated no more
Trains engineers and conductors have used radios to communicate with “headquarters” since the 1930s and 1940s. Still, radio coverage was inconsistent and erratic in more-isolated areas as well as electrically noisy urban areas. Providing a reliable link was especially challenging as the antenna sizes, and the installation reality limited types, and the train was likely moving as well. As “walkie-talkies” became available, these were soon adopted for communication among crew members.
In sharp contrast, today’s trains are fully connected in a sort of mobile, rolling “Internet of Things” (IoT) scenario (Figure 2).
2At the same time, the capabilities of these EOT units has grown as well. The first EOT devices were
“dumb” as they provided just a basic, high-intensity, flashing red light – the FRED. Soon, however, EOT devices became smarter with the ability to sense and report on the vital parameter of brake-line pressure to engineer in the cab via basic elementary.
The earlier “smart” EOT units only supported basic one-way communication of brake data to the locomotive. Now duplex two-way communication is used to enable the engineer to apply the brakes from both ends of the train in an emergency such as a blockage in the train’s brake line, which is preventing cutting the air pressure. Unlike a car, it’s the loss or removal of pressure that applies the brakes. By dropping the brake line pressure from both the front and rear, all of the train’s brakes can be applied simultaneously in an emergency.[Note that railroad brakes are normally “fail-safe,” as it takes the addition of pressure to release the brakes, while lack of pressure applies them – that was the highly innovative railroad-brake system developed by George Westinghouse in the 19th century. Any failure of the air compressor, valve, or brake line air-pressure line will cause the brakes to be applied.]
The most advanced EOT-device systems provide Information about air pressure, brake pressure, speed, and defects, and even location derived from an internal GPS receiver. Their routine update rate is every 30-40 seconds, but alarm conditions are reported immediately. This information is relayed between the rear of the train to a head-of-train (HOT) unit in-cab, (Figure 3).
This HOT unit (often referred to as a “Wilma” unit as a complement to “FRED” at the rear, a designation derived from the TV show “The Flintstones”!) is keyed to the assigned on-train EOT unit by entering the code number of the specific EOT device attached to the rear. It shows that simplicity and ease of use are paramount, as distracting and possibly overwhelming the engineer with too much non-critical data, as too many things to initialize is unacceptable. The full-duplex wireless link of modern designs uses coded signals at carrier frequencies such as 457.9375 MHz and 452.9375 MHz, which have been assigned in the spectrum to this application (Figure 4).
The caboose, which has historically marked the physical end of a freight train – whether just a few cars or many tens of cars – is now an obsolete artifact of railroad history. In its place, End of Train units monitor and relay key factors such as brake air pressure to the engineer and central control (in many cases), while also providing a basic flashing red light.
EOT devices were readily adopted as soon as they demonstrated their viability even in the harsh and demanding railroad environment. This was due to the considerable saving is they offered in up-front and operating costs by eliminating the caboose and personnel, as well as improving train operation efficiency while providing earlier warning of impending problems. They have become so “normal” in place of cabooses that accurately detailed models with a flashing light are available for HO-scale model railroads (Figure 5). The emergence of the FRED and advanced EOT devices (aided by Wilma) is yet another example of how multiple technologies and advances can combine to drive disruption of long-established practices and challenge systems of operation.
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