Flashing rear end device
Design and use
More than just a flashing red taillight, the FRED monitors functions such as brake line pressure and accidental separation of the train using a motion sensor, functions that would have been monitored by a crew in the caboose. The FRED transmits the data via a telemetry link to the Head-of-Train Device (HOT) in the locomotive, known colloquially among railroaders as a Wilma—the FRED is said to be "married to Wilma," a play on Fred Flintstone's wife from The Flintstones cartoon. A typical HOT contains a number of indicator lights indicating telemetry status and rear-end movement as well as a digital readout of the brake pipe pressure transmitted by the FRED. It also contains a toggle switch used to place the train's brakes into emergency from the rear end. In modern locomotives, the HOT is built into the locomotive's computer system, and the data is displayed on the engineer's computer screen.
Railroads have strict government-approved air brake testing procedures for various circumstances when making up trains in a yard or switching out cars en route. After a cut is made between cars in a train and the train is rejoined, in addition to other tests, the crew must verify that the brakes apply and release on the rear car (to ensure that all of the brake hoses are connected and the angle cocks, or valves, are opened). In most cases, the engineer is able to use data from the FRED to verify that the air pressure reduces and increases at the rear of the train accordingly, indicating that brake pipe continuity exists throughout the train.
Though the FRED greatly cuts labor costs as well as the costs of the purchase and upkeep of cabooses, railroad purist fans seem to agree that a train simply isn't complete without a caboose at the end. The Brotherhood of Conductors, and Brotherhood of Railroad Brakemen were also greatly affected by FRED seeing that this electronic Unit replaced 2 career jobs per Freight Train in Transit. Somewhat earning the nickname "fucking rear end detector." The widespread use of FREDs has made the caboose all but obsolete, but some roads still use cabooses where the train must be backed up, on short local runs, as rolling railroad police stations and transportation for right-of-way maintenance crews.
The first FRED use is attributed to Florida East Coast Railway in 1973; soon other Class I railroads began using FREDs as well. Early models were little more than a brake line connection, battery and flashing tail light. As their use became more widespread through the 1980s, FREDs were equipped with radio transmitters to send brake pressure data to a receiver in the locomotive. In order to alleviate the cost of constant battery replacements, ambient light sensors were added so the flashing light on the FRED would illuminate only after dark. Later models include a small turbine-powered electrical generator using air pressure from the brake line to power the FRED's radio and sensors.
The one-way communication of brake data from the FRED to the locomotive evolved into two-way communication that enables the engineer to apply the brakes from both ends of the train simultaneously in an emergency. This is useful in the event that a blockage in the train's brake pipe is preventing all of the cars in the train from going into an emergency application. Such a situation could be dangerous, as stopping distance increases with fewer functional brakes. Dumping the brake pipe pressure from both the front and rear of the train ensures that the entire train applies its brakes in emergency. Other electronics within the FRED were also enhanced and many now include GPS receivers as well as the two-way radio communications.
Railfans and railway photographers sometimes use FREDs as early warning systems to indicate the approach of an impending train. FREDs in North America operate on the 452.9375/457.9375 MHz frequency pair with the exception of those operated by Norfolk Southern Railway, which uses Association of American Railroads (AAR) channel 67 (161.115 MHz). Railfans often program these frequencies into their scanners, which can provide a handy indicator of train activity (usually 2-5 miles, transmitting at 2 watts).
- Lustig, David (August 2006). "End-of-train devices keep on evolving in back". Trains 66 (8): p 18. ISSN 0041-0934.