Flashing Rear-end Device - Design and Use

Design and Use

The 'smart' FRED devices monitor functions such as brake line pressure and accidental separation of the train using a motion sensor, functions that were previously monitored by a crew in the caboose. The FRED transmits the data via a telemetry link to the Head-of-Train Device (HTD) in the locomotive, known colloquially among railroaders as a 'Wilma'. This is a play on the first name of the wife of cartoon character Fred Flintstone. In Canada, this device is known as an SBU (Sense and Braking Unit).

A typical HTD contains several lights indicating telemetry status and rear end movement, along with a digital readout of the brake line pressure from the FRED. It also contains a toggle switch used to initiate an emergency brake application from the rear end. In modern locomotives, the HTD 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 assembling trains 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 proper brake pipe continuity. This device is said to constitute a fail-safe condition.

The FRED reduced labor costs, as well as the costs of the purchase and upkeep of cabooses. The Brotherhood of Conductors, and Brotherhood of Railroad Brakemen were also greatly affected by FRED, as this electronic unit replaced two crewmen per train. The widespread use of FREDs has made the caboose nearly obsolete. Some roads still use cabooses where the train must be backed up, on short local runs, as rolling offices, or railroad police stations and as transportation for right-of-way maintenance crews.