Trap points and a sand drag protect the exit of a station passing loop (left), while catch points stop vehicles from running away down a steep slope (right).

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 out of control on steep slopes (known as runaways). Trap points are used to protect main railway lines from unauthorised vehicles moving onto them from sidings or branch lines. 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. In rail terminology, a loop can mean one of two configurations: a stretch of rail track that provides a place for a train to halt temporarily while other trains pass on an adjacent main line . ... This article does not cite any references or sources. ... A railroad switch is a mechanical installation enabling trains to be guided from one set of rail tracks (or tramway tracks) to another. ... Warning signs, such as this one, can improve safety awareness. ... A railroad car (or, more briefly, car, not to be confused with railcar), also known as an item of rolling stock, is a vehicle on a railroad (or railway) that is not a locomotive — one that provides another purpose than purely haulage, although some types of car are powered. ... Two rail welds in continuous welded rail in Wisconsin. ... A siding, in general rail terminology, refers to a section of rail used to store stationary rolling stock perhaps whilst it is loaded or unloaded, or alternatively, a short length of rail that provides access to and from factories, mines, quarries, wharves, etc. ... A branch line is a relatively minor railway line which branches off a more important through route. ...

A derail is another device used for the same purposes as catch and trap points. Derail device installed at an industry, complete with Blue Flag protection -- Nichols, Florida. ...

Trap points

Diagram showing the use of trap points to protect the main line at the exit of a siding.

An insulated track circuit interrupter fitted to trap points.

Trap points are found at the exit from a siding or where a secondary track joins a main line. A facing turnout is used to prevent any unauthorised movement that may otherwise obstruct the main line. ^[1] 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. ^[2] In the United Kingdom, the use of trap points at siding exits is required by government legislation.^[2] A siding, in general rail terminology, refers to a section of rail used to store stationary rolling stock perhaps whilst it is loaded or unloaded, or alternatively, a short length of rail that provides access to and from factories, mines, quarries, wharves, etc. ... Facing and trailing are terms used to describe railway turnouts in respect to whether they are divergent or convergent. ...

An unauthorised movement may be due to a runaway wagon, or may be a train passing a signal at danger. When a signal controlling passage onto a main line is set to "stop", 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. A railroad car (or, more briefly, car, not to be confused with railcar), also known as an item of rolling stock, is a vehicle on a railroad (or railway) that is not a locomotive — one that provides another purpose than purely haulage, although some types of car are powered. ... Two-aspect signal at danger In railway terminology, a Signal Passed At Danger or SPAD describes an event where a train has run beyond its allocated signal block without authority, as indicated by a lineside signal showing danger. ... A signal is a mechanical or electrical device that indicates to train drivers or engineers information about the state of the line ahead, and therefore whether he or she must stop or may proceed, or instructions on what speed the train may go. ... Interlocking in railway terminology (US) is a term used to describe an at-grade crossing or other junction of two or more railroads, or any railroad switching complex in which the switches and the signals controlling train movement over those switches is interlocked so that it is impossible to give...

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 circuited, then a track circuit interrupter will be fitted to one of the run-off rails in order to break the track circuit and set main line signals to 'danger'. It has been suggested that Rail circuits be merged into this article or section. ...

Types of trap points

There are several different ways of constructing trap points: ^[2]

• 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 furthest 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 gradient of the siding, and whether locomotives enter the siding. ^[2] A Buffer stop is a device to prevent railway vehicles from going past the end of a section of track. ... A grade (or gradient) is the pitch of a slope, and is often expressed as a percent tangent, or rise over run. It is used to express the steepness of slope on a hill, roof, or road, where zero indicates level (with respect to gravity) and increasing numbers correlate to... Great Western Railway No. ...

Types of trap points

Double trap points protecting the South Wales Main Line at the exit of Stoke Gifford Rail Yard near Bristol Parkway railway station. The South Wales Main Line is a branch of the Great Western Main Line. ... Bristol Parkway railway station is a railway station on the northern edge of Bristol (England), at Stoke Gifford in South Gloucestershire. ...

Double trap points with much longer rails, at Castle Cary railway station. Castle Cary station serves the town of Castle Cary in Somerset. ...

A trap road with buffer stops at the railway station of Allersberg, on the Nuremberg-Munich high-speed rail line. 72,4 Reichertshofen (Oberbayern) 60,2 Rohrbach (Ilm) 49,7 Pfaffenhofen 43,8 Reichertshausen (Ilm) 40,2 Paindorf 36,4 Petershausen (Oberbayern) 17,8 Dachau 0,0 München Hauptbahnhof An ICE 1 leaves Schellenberg-tunnel to pass through the station of Kinding at 250 km/h In July 2006...

Catch points

Catch points are used where track follows a rising gradient. They are used to derail (or "catch") any unauthorised vehicles travelling down the gradient.^[1] This may simply be a vehicle that has accidentally been allowed to runaway down the slope, or could be a wagon that has decoupled from its train. ^[2] In either case, the runaway vehicle could collide with a train further down the slope, causing a serious accident. A grade (or gradient) is the pitch of a slope, and is often expressed as a percent tangent, or rise over run. It is used to express the steepness of slope on a hill, roof, or road, where zero indicates level (with respect to gravity) and increasing numbers correlate to... In physics, decoupling is the general phenomenon in which the interactions between some physical objects (such as elementary particles) disappear. ...

Catch points may consist of a full turnout or a single switch blade. In some cases, on a track that is only traversed by uphill traffic, 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 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 springs. ^[2] 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 word turnout can refer to: Voter turnout A railroad switch or point This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Rail tracks. ... Facing and trailing are terms used to describe railway turnouts in respect to whether they are divergent or convergent. ... The word turnout can refer to: Voter turnout A railroad switch or point This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Helical or coil springs designed for tension A spring is a flexible elastic object used to store mechanical energy. ...

The use of catch points became widespread in the United Kingdom after the Abergele train disaster, where runaway wagons containing 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, continuous automatic brakes, which automatically stop any vehicles separated from their train, were widely adopted, making catch points largely obsolete. The Abergele Train Disaster in 1868 was the first major railway disaster in Britain. ... Kerosene or paraffin is a colorless flammable hydrocarbon liquid. ... Express trains (also sometimes referred to as fast trains) are a form of rail service. ... Brakes are used on railway trains to bring the train to a standstill. ...

Sand drag

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 siding simply leading to a mound of sand, gravel or other granular material, or a siding where the rails are within sand-filled troughs.^[1] This method of stopping a vehicle travelling at speed is preferred over a buffer stop as there is less shock to the vehicle involved. ^[2] A siding, in general rail terminology, refers to a section of rail used to store stationary rolling stock perhaps whilst it is loaded or unloaded, or alternatively, a short length of rail that provides access to and from factories, mines, quarries, wharves, etc. ... Patterns in the sand Sand is a granular material made up of fine rock particles. ... Gravel (largest fragment in this photo is about 4 cm) Gravel is rock that is of a certain particle size range. ... A Buffer stop is a device to prevent railway vehicles from going past the end of a section of track. ... In mechanics, a shock is a sudden acceleration or deceleration caused, for example, by impact or explosion. ...

References

1. ^ ^{a b c} Glossary of Signalling Terms, Railway Group Guidance Note GK/GN0802, Issue One (PDF). Rail Safety and Standards Board (UK) (April 2004). Retrieved on 2007-02-18.
2. ^ ^{a b c d e f g} in D. H. Coombs: British Railway Track: Design, Construction and Maintenance, 4th edition (1971), The Permanent Way Institution, pp. 150-152. 

Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 49th day of the year in the Gregorian calendar. ...

External links

• Illustrated explanation of catch points at Springwell