A derail or derailer is a device used to prevent fouling (blocking or compromising) of a rail track (or collision with anything present on the track, such as a person, or a train) by unauthorized movements of trains or unattended

rolling stock The term rolling stock in the rail transport industry refers to railway vehicles, including both powered and unpowered vehicles: for example, locomotives, freight and passenger cars (or coaches), and non-revenue cars. Passenger vehicles can ...

. The device works by

derailing In rail transport, a derailment occurs when a rail vehicle such as a train comes off its rails. Although many derailments are minor, all result in temporary disruption of the proper operation of the railway system and they are a potentially ...

the equipment as it rolls over or through it. Although accidental derailment is damaging to equipment and track, and requires considerable time and expense to remedy, derails are used in situations where there is a risk of greater damage to equipment, injury or death if equipment is allowed to proceed past the derail point.

Applications

Derails may be applied: *where sidings meet main lines or other through tracks *at junctions or other crossings to protect the

interlocking In railway signalling, an interlocking is an arrangement of signal apparatus that prevents conflicting movements through an arrangement of tracks such as junctions or crossings. The signalling appliances and tracks are sometimes collectively re ...

against unauthorized movement *temporarily at an area where crews are working on a rail line *approaching a drawbridge, dead end, or similar hazard.

Design

There are four basic forms of derail.

Wedge

The most common form is a wedge-shaped piece of steel which fits over the top of the rail. If a car or locomotive attempts to roll over it, the wheel flange is lifted over the rail to the outside, derailing it. When not in use, the derail folds away, leaving the rail unobstructed. It can be manually or remotely operated; in the former case it will have a lock applied to prevent it from being moved by unauthorized personnel. This type is common on North American railroads.

Split rail

The second type of derail is the "split rail" type. These are basically a complete or partial

railroad switch A railroad switch (), turnout, or ''set ofpoints () is a mechanical installation enabling railway trains to be guided from one track to another, such as at a railway junction or where a spur or siding branches off. The most common t ...

which directs the errant rolling stock away from the main line. This form is common throughout the UK, where it is called trap points or

catch points Catch points and trap points are types of turnout which act as railway safety devices. Both work by guiding railway carriages and trucks from a dangerous route onto a separate, safer track. Catch points are used to derail vehicles which are ou ...

Portable

The third type of derail is the portable derail, and is used by railroad mechanical forces, as well as some industries. This is often used in conjunction with blue flag rules (meaning equipment on the track must not be moved, as workers are on or near the equipment) and is temporary in nature. They are placed onto one side of the rail with the derail pointed to the outside of the track. Then there is a part of the derail that is able to be tightened down to the rail and then secured with a locking mechanism. If the derail is left unlocked for any reason or does not have a locking mechanism deployed then the owner of the derail can face substantial fines if found by an FRA inspector (.)

Powered

The fourth type of derailer is the powered or motorized derailer, electronically powered through an actuator. This type of derailer can be controlled remotely from an external control panel or manually. It is commonly installed as a part of

Depot Personnel Protection System A Depot Protection System (''DPS'') is a system designed to protect staff and equipment by ensuring the safe and controlled movement of rail vehicles into and out of train maintenance depots, a process sometimes known as train movements or shunti ...

s, to ensure personnel safety in maintenance workshops and depots.

Failures

Derails have failed on occasion, such as on April 1, 1987, at Burnham,

Illinois Illinois ( ) is a state in the Midwestern United States. Its largest metropolitan areas include the Chicago metropolitan area, and the Metro East section, of Greater St. Louis. Other smaller metropolitan areas include, Peoria and Rockf ...

, when an unsecured car in a siding defeated a derail and fouled the mainline. Due to rusty rails, the car then failed to shunt the

track circuit A track circuit is an electrical device used to prove the absence of a train on rail tracks to signallers and control relevant signals. An alternative to track circuits are axle counters. Principles and operation The basic principle behind t ...

that should have put block signals to "stop". On May 15, 2001, CSX 8888, pulling a train of 47 cars including some loaded with hazardous chemicals, ran uncontrolled for two hours at up to . A portable derail was used but failed. On April 20, 2017, three workers were killed in an accident on the

Englewood Railway Englewood Railway was a logging railroad on northern Vancouver Island, Canada. Headquartered in Woss, British Columbia, the line ran from Vernon Lake, through Woss, and past Nimpkish Lake Provincial Park to Beaver Cove. It was the last operati ...

Woss Woss, also commonly known as Woss Lake after the nearby lake of the same name, is a small village in the Nimpkish Valley, located southeast of Port McNeill and north of Campbell River on Highway 19, in northeastern Vancouver Island, British C ...

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

when 11 runaway railcars full of logs crashed into them and their equipment while they were working on the line. The railcars had become uncoupled at the top of the hill and as they rolled out-of-control down the hill, they overpowered the derails which had been installed incorrectly and into rotting rail ties.

References

* * * {{Rail tracks Rail infrastructure