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.[1] The device works by derailing 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.
Derailers may be operated remotely (motorized) or manually with a lever. For safe operation, a manually operated derailer may be locked with a key or locked/verified remotely.
A less 'violent' alternative, more common on busy lines, have a switch that diverges offending trains onto a safer route or a short stretch of rail towards something suitable to stop the train, like a buffer stop or sand bank. These could be tagged as normal switches. The diverging track could perhaps be tagged with service=runaway or catch_point in addition to the normal railway=rail.
Node Mapping
Create a node 
on the drawn railway line where the derail is located, mark
it as railway=derail and add an appropriate description.
Appropriate description
Marking of the turnout (if available and marked) *= should start with a
country code or operator prefix, or a standard like Us-BNSF: xxx, where BNSF
represents the railway operator BNSF Rail and xxx stands for the turnout
number.
| Explanatory notes on the markings in the tables:
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| ■ ... Required
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■ ... Recommended
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■ ... Optional
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* ... Selection
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# ... Value
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■ direction=*
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- direction of derail per drawn line
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… forward
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… movement to derail per line drawn ↗
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… backward
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… movement to derail per reverse of line drawn ↗
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… both
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… movement in any direction per line drawn ↗
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■ railway:derail=*
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- type of derail
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… Wedge
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… wedge derail (flop over or temporary) ↗
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… Trap Point
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… incomplete switch (only the switch points) ↗
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… Catch Point
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… turnout (with a short section of track) ↗
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… Sand Drag
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… earth derail (a mound of earth) ↗
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■ railway:local_operated=*
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- is the derail operated at the derail
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* = yes
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… the derail can be controlled locally (ie. you can manually use a lever on site)
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* = no
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… the derail can not be controlled locally (it must be operated remotely)
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May also tag these with..
■ railway:derail:control=*
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- how is the derail controled
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* = manual
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... hands are used to throw
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* = manual_locked
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... hands are used to throw and is locked
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* = remote_locked
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... is remotely locked (hand thrown or remotely)
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* = remote
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... is operated completely remotely
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■ railway:derail:electric=*
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- has electrical mechanism throw
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* = yes
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... yes, it can throw with power
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* = no
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... no, it does not throw with power and needs a human
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■ railway:derail:local_operated=*
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- is the device operated at the derail
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* = yes
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... yes, there is a lever at the derail to throw the derail
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* = no
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... no, the switch is thrown from a switch box, interchange or remotely
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Tags used in combination
name=*ref=* The reference used for this derailer. Usually digits and/or letters.railway:derail=* Suggested values: wedge, trap_point, catch_point.railway:derail:direction=forward/backward/both – Direction in which rolling stock can be derailed, relative to how the way is drawn in OSM.railway:derail:electric=yes/no – Electric motor?railway:local_operated=yes/no – Is the it operated in field (yes) or by a person at the signal box (no)?operator=* Who may have the key or from which signal controller has the remote control.
Possible rendering
suggested by User:Chrisana13
See also
railway = derail
suggested by User:Chrisana13