A railroad switch (AE), turnout, or [set of] points (CE) 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.
An overhead line or overhead wire is an electrical cable that is used to transmit electrical energy to electric locomotives, trolleybuses or trams. The generic term used by the International Union of Railways for the technology is overhead line. It is known variously as overhead catenary, overhead contact line (OCL), overhead contact system (OCS), overhead equipment (OHE), overhead line equipment, overhead lines (OHL), overhead wiring (OHW), traction wire, and trolley wire.
A level crossing is an intersection where a railway line crosses a road, path, or airport runway, at the same level, as opposed to the railway line crossing over or under using an overpass or tunnel. The term also applies when a light rail line with separate right-of-way or reserved track crosses a road in the same fashion. Other names include railway level crossing, railway crossing, grade crossing or railroad crossing, road through railroad, criss-cross, train crossing, and RXR (abbreviated).
Railway signalling (BE), also called railroad signaling (AE), is a system used to control the movement of railway traffic. Trains move on fixed rails, making them uniquely susceptible to collision. This susceptibility is exacerbated by the enormous weight and inertia of a train, which makes it difficult to quickly stop when encountering an obstacle. In the UK, the Regulation of Railways Act 1889 introduced a series of requirements on matters such as the implementation of interlocked block signalling and other safety measures as a direct result of the Armagh rail disaster in that year.
A third rail, also known as a live rail, electric rail or conductor rail, is a method of providing electric power to a railway locomotive or train, through a semi-continuous rigid conductor placed alongside or between the rails of a railway track. It is used typically in a mass transit or rapid transit system, which has alignments in its own corridors, fully or almost fully segregated from the outside environment. Third-rail systems are usually supplied from direct current electricity.
Wigwag is a nickname for a type of railroad grade crossing signal once common in North America, referring to its pendulum-like motion that signaled a train's approach. The device is generally credited to Albert Hunt, a mechanical engineer at Southern California's Pacific Electric (PE) interurban streetcar railroad, who invented it in 1909 for safer railroad grade crossings. The term should not be confused with its usage in Britain, where "wigwag" generally refers to alternate flashing lights, such as those found at modern level crossings.
Rail transport terms are a form of technical terminology applied to railways. Although many terms are uniform across different nations and companies, they are by no means universal, with differences often originating from parallel development of rail transport systems in different parts of the world, and in the national origins of the engineers and managers who built the inaugural rail infrastructure. An example is the term railroad, used in North America, and railway, generally used in English-speaking countries outside North America and by the International Union of Railways. In English-speaking countries outside the United Kingdom, a mixture of US and UK terms may exist.
Cab signaling is a railway safety system that communicates track status and condition information to the cab, crew compartment or driver's compartment of a locomotive, railcar or multiple unit. The information is continually updated giving an easy to read display to the train driver or engine driver.
A crossbuck is a traffic sign used to indicate a level railway crossing. It is composed of two slats of wood or metal of equal length, fastened together on a pole in a saltire formation. Crossbucks are sometimes supplemented by electrical warnings of flashing lights, a bell, or a boom barrier that descends to block the road and prevent traffic from crossing the tracks.
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.
The 1995 Fox River Grove bus–train collision was a grade crossing collision that killed seven students riding aboard a school bus in Fox River Grove, Illinois, on the morning of October 25, 1995. The school bus, driven by a substitute driver, was stopped at a traffic light with the rearmost portion extending onto a portion of the railroad tracks when it was struck by a Metra Union Pacific Northwest Line train en route to Chicago.
An axle counter is a system used in railway signalling to detect the clear or occupied status of a section of track between two points. The system generally consists of a wheel sensor and an evaluation unit for counting the axles of the train both into and out of the section. They are often used to replace a track circuit.
A slide fence is a structural fence designed to physically stop falling rocks from reaching the tracks. The fence is designed to retain a rockslide if possible, but if it is displaced by such it also can cause the signaling system to display a restrictive aspect to approaching trains.
Digital model railway control systems are an alternative to control a layout and simplify the wiring and add more flexibility in operations. A number of control systems are available to operate locomotives on model railways. Analog systems where the speed and the direction of a train is controlled by adjusting the voltage on the track are still popular while they have recently given way to control systems based on computer technology.
ALSN is a train control system used widely on the main lines of the ex-Soviet states. It uses modulated pulses inducted into rails similar to the Italian RS4 Codici and American Pulse Code Cab Signaling. On high-speed lines the variant ALS-EN (АЛС-ЕН) is used which takes advantage of a double phase difference modulation of the carrier wave.
The intermittent inductive automatic train stop is a train protection system used in North American mainline railroad and rapid transit systems. It makes use of magnetic reluctance to trigger a passing train to take some sort of action. The system was developed in the 1920s by the General Railway Signal Company as an improvement on existing mechanical train stop systems and saw limited adoption before being overtaken by more advanced cab signaling and automatic train control systems. The system remains in use after having been introduced in the 1920s.
There are around 6,000 level crossings in the United Kingdom, of which about 1,500 are public highway crossings. This number is gradually being reduced as the risk of accidents at level crossings is considered high. The director of the UK Railway Inspectorate commented in 2004 that "the use of level crossings contributes the greatest potential for catastrophic risk on the railways." The creation of new level crossings on the national network is banned, with bridges and tunnels being the more favoured options. The cost of making significant reductions, other than by simply closing the crossings, is substantial; some commentators argue that the money could be better spent. Some 5,000 crossings are user-worked crossings or footpaths with very low usage. The removal of crossings can improve train performance and lower accident rates, as some crossings have low rail speed limits enforced on them to protect road users. In fact, between 1845 and 1933, there was a 4 miles per hour (6.4 km/h) speed limit on level crossings of turnpike roads adjacent to stations for lines whose authorising act of Parliament had been consolidated in the Railways Clauses Consolidation Act 1845 although this limit was at least sometimes disregarded.
In electronics, power amplifier classes are letter symbols applied to different power amplifier types. The class gives a broad indication of an amplifier's characteristics and performance. The first three classes are related to the time period that the active amplifier device is passing current, expressed as a fraction of the period of a signal waveform applied to the input. This metric is known as conduction angle (θ). A class A amplifier is conducting through all the period of the signal (θ=360°); Class B only for one-half the input period (θ=180°), class C for much less than half the input period (θ<180°). Class D amplifiers operate their output device in a switching manner; the fraction of the time that the device is conducting may be adjusted so a pulse-width modulation output can be obtained from the stage.
The E-signal is a type of grade crossing signal used in Sweden on very low-traffic roads crossing a railroad track, when the same landowner owns the property on both sides of the railway track and only a few residential buildings and no facility of public interest can be reached from the road. An e-signal operates in the opposite fashion of a conventional grade crossing signal: it is lit when no train is approaching the crossing, and when a train approaches, it extinguishes approximately 30-60 seconds before the train's arrival. This is intended to provide a 'fail safe' function, in the event the power has failed or the signal bulb has blown; e-signal mountings are always supplemented with an information plate indicating the function of the signal. It is supplied from the track circuit which supply a voltage to one rail in order to detect trains. When there is a train there can be no voltage difference between the rails. This means that no external uninterruptible power supply is needed and the installation cost is reduced a lot, and many more can be installed within limited budgets.
Designs of level crossings, where railway lines cross roads or other paths, vary country-to-country.
