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((Short description|Railway points used as safety devices))
((refimprove|date=April 2017))
[[File:Catch trap drag.jpg|thumb|right|Trap points and a sand drag (left) and catch points (right) protect the entrance to a single track on a steep grade.]]
'''Catch points''' and '''trap points''' are types of [[railroad switch|points]] which act as [[railway]] [[safety]] devices. Both work by guiding [[railroad car|railway carriages and trucks]] from a dangerous route onto a separate, safer track. Catch points are used to [[derailment|derail]] vehicles which are out of control (known as [[Runaway train|''runaways'']]) on steep slopes. Trap points are used to protect [[rail terminology#M|main railway lines]] from unauthorised vehicles moving onto them from [[rail siding|sidings]] or [[branch line]]s. Either of these track arrangements may lead the vehicles into a '''sand drag''' or '''safety siding''', track arrangements which are used to safely stop them after they have left the main tracks.

A [[derail]] is another device used for the same purposes as catch and trap points.

== Trap points ==

[[File:Trap points.png|thumb|right|Diagram showing the use of trap points to protect the main line at the exit of a siding]]

[[File:Track circuit interrupter.jpg|thumb|right|An insulated [[track circuit interrupter]] fitted to trap points]]

''Trap points'' are found at the exit from a [[rail siding|siding]] or where a secondary track joins a main line. A [[facing and trailing|facing]] turnout is used to prevent any unauthorised movement that may otherwise obstruct the main line.<ref name=signalling_glossary>((cite web
 |title=Glossary of Signalling Terms, Railway Group Guidance Note GK/GN0802, Issue One 
 |publisher=Rail Safety and Standards Board (UK) 
 |date=April 2004 
 |url=http://www.rgsonline.co.uk/docushare/dsweb/Get/Rail-41325/gn0802.PDF 
 |access-date=2007-02-18 
 |url-status=dead 
 |archive-url=https://web.archive.org/web/20160129083621/http://www.rssb.co.uk/ 
 |archive-date=2016-01-29 
))  </ref> The trap points also prevent any damage that may be done by a vehicle passing over points not set for traffic joining the main line.<ref name=british_railway_track>((cite book
  |editor=D. H. Coombs 
  |title=British Railway Track: Design, Construction and Maintenance 
  |edition=4th edition (1971)
  |publisher=The Permanent Way Institution
  |pages=150–152 ))</ref> In the [[United Kingdom]], the use of trap points at siding exits is required by government legislation.<ref name=british_railway_track/>

An unauthorised movement may be due to a runaway [[Railroad car|wagon]], or may be a train [[signal passed at danger|passing a signal at danger]]. When a [[Railway signal|signal]] controlling passage onto a main line is set to "danger", the trap points are set to derail any vehicle passing that signal. [[Interlocking]] is used to make sure that the signal cannot be set to allow passage onto the main line until the trap points have been aligned to ensure this movement can take place.

Trap points should preferably be positioned to ensure that any unauthorised vehicle is stopped a safe distance from the main line. However, due to space limitations, it is not always possible to guarantee this.

If the lines are [[track circuit]]ed and a wagon or train using the catchpoint could foul an adjacent line, then a [[track circuit interrupter]] will be fitted to one of the run-off rails. When a train runs off it will break the track circuit and set main line signals to 'danger'.

=== Types ===

There are several different ways of constructing trap points:<ref name=british_railway_track/>
* A ''single tongue trap'' consists of only one switch rail, leading away from the main line to a short tongue of rail. This is usually placed in the rail farthest from the main line.
* ''Double trap points'' are a full turnout, leading to two tongues. Usually the tongue nearer the main line is longer than the other.
* ''Trap points with a crossing'' are double trap points where the tongues of rail are longer, so that the trap point rail nearest the main line continues over the siding rail with a common crossing or frog.
* A ''trap road with stops'' is a short dead-end siding leading to some method of stopping a vehicle, such as a sand drag or [[buffer stop]].
* ''Wide to gauge trap points'' have switches that work in opposite directions and are therefore either both open or both closed. Vehicles derailed at these points will tend to continue in a forward direction rather than being thrown to one side. Wide to gauge points are typically found on sidings situated between running lines.
The type of trap points to be used depends on factors such as the [[Grade (slope)|gradient]] of the siding, and whether [[locomotive]]s enter the siding.<ref name=british_railway_track/>
* ''Independent switches'' are a kind of wide to gauge switch which are part of two separate crossovers. There are three positions: part of crossover A to left; wide to gauge switches; part of crossover B to right. A good place to view these independent switches are at both ends of Platforms 1 and 2 at [[Hornsby railway station]], Sydney.

<gallery caption="Types of trap points" class=center>
File:StokeGiffordYard-catchpoints.jpg|Double trap points protecting the [[South Wales Main Line]] at the exit of Stoke Gifford Rail Yard near [[Bristol Parkway railway station]]
File:Castle Cary catch points - 02.jpg|Double trap points with much longer rails, at [[Castle Cary railway station]]
File:Schutzweiche.jpg|A trap road with buffer stops at the railway station of ''Allersberg'', on the [[Nuremberg–Munich high-speed railway]]
Strasbourg_aiguillage-déraillant.jpg|Trap point in France
</gallery>

[[File:Trap points - R162020 201223 Clitheroe UK.png|thumb|[[Rail Accident Investigation Branch|RAIB]] accident investigation image of a cement wagon derailed by trap points at Clitheroe, 9 March 2020, successfully protecting the adjacent running lines (left)]]

''Catch points'' are used where track follows a rising [[Grade (slope)|gradient]]. They are used to [[Derailment|derail]] (or "catch") any unauthorised vehicles travelling down the gradient.<ref name=signalling_glossary/> This may simply be a vehicle that has accidentally been allowed to run away down the slope, or could be a wagon that has [[railway coupling|decouple]]d from its train.<ref name=british_railway_track/> In either case, the runaway vehicle could collide with a train farther down the slope.

Catch points may consist of a full [[Railroad switch|turnout]] or a single switch blade. In some cases, on a [[Rail tracks|track]] that is only traversed by uphill traffic, [[facing and trailing|trailing]] point blades are held in a position to derail any vehicle travelling downhill. However, any traffic travelling in the correct (uphill) direction can pass over the [[Railroad switch|turnout]] safely, pushing the switch blades into the appropriate position. Once the wheels have passed, the catch points are forced back into the derailing position by [[Spring (device)|spring]]s.<ref name=british_railway_track/> In these cases, a lever may be provided to temporarily override the catch points and allow safe passage down the gradient in certain controlled circumstances.

The use of catch points became widespread in the [[United Kingdom]] after the [[Abergele rail disaster]] (1868), where runaway wagons containing [[Kerosene|paraffin oil]] (kerosene) collided with an [[express train]]. Catch points continued to be used in the UK until the mid-20th century. At this time, [[Brake (railway)|continuous automatic brakes]], which automatically stop any vehicles separated from their train, were widely adopted, making catch points largely obsolete.((cn|date=October 2020))

== Wide to gauge catch points ==

Sometimes a track is located between two other tracks that are converging, and there is nowhere for a catchpoint to divert a train to.  In such cases, a pair of single catchpoints of left and right hand may be provided to derail the overrunning train without directing it to either side.  The two blades of an ordinary turnout may also be operated separately for the same purpose.

Examples would be the north and south ends of platforms 1 and 2 at [[Hornsby railway station|Hornsby]] in [[New South Wales]]((citation needed|date=April 2013)).

== Sand drag ==
((redirect|Sand drag|off-road drag racing|Drag racing))
[[Image:QC-STM GarageBeaugrand 20040706-132759 VoieEssai.jpg|thumb|right|View of a track from a '''sand drag''', in the [[Montreal Metro]] beyond the [[Honoré-Beaugrand (Montreal Metro)|Honoré-Beaugrand station terminus]]]]

In some cases, catch points and trap points direct vehicles into a ''sand drag'' or ''safety siding'', also sometimes called an ''arrestor bed''. This may be a [[Rail siding|siding]] simply leading to a mound of [[sand]], [[gravel]] or other granular material, or a siding where the rails are within sand-filled troughs.<ref name=signalling_glossary/> This method of stopping a vehicle travelling at speed is preferred over a [[buffer stop]] as there is less [[Shock (mechanics)|shock]] to the vehicle involved.<ref name=british_railway_track/>

== Chock block ==

A cheap and simple alternative to catch points or a derail is a chock block, which is a piece of timber that can be positioned and locked over one of the rails at the end of a siding to protect the main line from runaways. In order for the siding to be used the chock block must be removed.<!-- No kidding! -->

== Effectiveness ==
[[File:British Rail Class 165 165124 derailed at Paddington, 2016.jpg|thumb|A [[British Rail Class 165]] that was derailed by a set of trap points at [[London Paddington station]], June 2016. The train suffered severe damage to the rear driving unit and also damaged a [[stanchion]] after the derailed train collided with it.]]
Because catch points are rarely needed, it is not always clear whether they will in fact derail a runaway train effectively and as safely as possible. For example, use of catch points to derail a train that had [[Signal passed at danger|passed a signal at danger]] at [[Paddington railway station|London Paddington]] station in June 2016 resulted in the empty train, a [[British Rail Class 165|Class 165]], hitting and severely damaging  an [[Overhead line|overhead line electrification]] stanchion, causing all services to and from the station to be halted for hours.<ref>((cite news|last1=Chandler|first1=Mark|title=Paddington station train derailment: Fire brigade called in as incident causes travel chaos|url=https://www.standard.co.uk/news/transport/paddington-station-fire-brigade-called-in-as-train-derailment-causes-travel-chaos-a3273941.html|access-date=17 June 2016|work=Evening Standard))</ref>

== Accidents ==
In 2010, in snowy conditions, at [[Rail accidents at Carrbridge#2010 freight train derailment|Carrbridge]], a [[British Rail Class 66|Class 66]] passed a red signal as well as catch points, leading to the train going down the embankment, injuring the two crew on board.<ref>((cite web |title=Derailment of a freight train at Carrbridge |url=https://www.gov.uk/raib-reports/derailment-of-a-freight-train-at-carrbridge-badenoch-and-strathspey |website=GOV.UK |publisher=RAIB |access-date=13 July 2021))</ref>

== See also ==
* [[Buffer stop]]
* [[Derail]]
* [[Runaway train]]
* [[Runaway truck ramp]]
* [[Runway safety area]] (RSA/RESA) for airplanes

== References ==
((reflist))

== External links ==
((commons category))
* [http://www.bowesrailway.co.uk/SiteTour/Sprngwel/b_swell0301.htm Illustrated explanation of catch points at Springwell] ((Webarchive|url=https://web.archive.org/web/20050509041351/http://www.bowesrailway.co.uk/SiteTour/Sprngwel/b_swell0301.htm |date=2005-05-09 ))
* [https://www.youtube.com/watch?v=Yr5EztEPJS8 Steam locomotive derailed by catch points] at [[Great Central Railway (heritage railway)|Great Central Railway]] &mdash; video footage on YouTube

((Rail tracks)) 
((Railwaysignalling))

[[Category:Railway safety]]
[[Category:Railway track layouts]]

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