A funicular (//, /( ) -/, /-/) is a grade-separated fixed guideway transit system powered by a cable traction designed for steep inclines. A funicular uses two counterbalanced passenger cars attached to the opposite ends of a cable, which is looped over a pulley at the upper end of the track.
A funicular's two cars move in concert: as one ascends, the other descends simultaneously, an arrangement that distinguishes a funicular from other cable-guided transportation systems — e.g., a single-car inclined elevator.
In a funicular both cars (or trains) are permanently connected to the opposite ends of the same cable, known as a haul rope. At the engine room at upper end of the track the haul rope runs through a system of pulleys. Sheave wheels guide the cable along the track to and from the drive mechanism and the cars. The rope pulls one car upwards while the other car descends the slope as the other end of the rope is paid out from the engine mechanics. This arrangement counterbalances the two cars and thereby reduces the energy needed to lift the ascending car. 
Typically in a modern funicular the propulsion is provided by an electric motor which is linked via a speed-reducing gearbox to a large pulley – a drive bullwheel. The bullwheel in its turn transfers its torque to the haul rope by friction. The bullwheel has two grooves: after the first half turn around it the cable returns back via an auxiliary pulley. High friction liners are used in modern installations to enhance the friction between the bullwheel and the cable.
For emergency and service purposes two sets brakes are used at the engine room: the emergency brake grips directly the bullwheel, the service brake is mounted at the high speed shaft of the gear. In a case of emergency the cars are also equipped by spring applied hydraulically opened rail brakes.
Early funiculars used two parallel straight tracks, four rails, with separate station platforms for each vehicle. The tracks are laid with sufficient space between them for the two cars to pass at the midpoint. Three-rail arrangement was also used to overcome the half-way passing problem. Examples of this type of track layout are the Duquesne Incline in Pittsburgh, Pennsylvania, and most cliff railways in the UK.
In layouts using three rails, the middle rail is shared by both cars, like in the early version of the Petřín funicular in Prague. The three-rail layout is wider than the two-rail layout, but the passing section is simpler to build. If a rack for braking is used, that rack can be mounted higher in a three-rail layout, making it less sensitive to choking in snowy conditions.
Some four-rail funiculars have the upper and lower sections interlaced and a single platform at each station. The Hill Train at Legoland, Windsor, is an example of this configuration.
The track layout can also be changed during the renovation of a funicular, and often four-rail layouts have been rebuilt as two- or three-rail layouts; e.g., the Wellington Cable Car in New Zealand was rebuilt with two rails.
Abt automatic turnout
The Swiss engineer Carl Roman Abt invented the method that allows cars to be used with a two-rail configuration. The cars, in this case, have their wheelsets of a rather unconventional design: the outboard wheel has flanges on both sides whereas the inboard wheel is unflanged.
One car has its dual-flanged wheels on the left side, so it follows the leftmost rail. The other car – on the right side, and it follows the rightmost rail. Given that the left car always goes through the passing loop at its left branch and the right car at its right branch. The car's unflanged wheels are considerably wider than their opposites which allows them to roll over the turnouts easily from one rail to another and above the cables.
This system does not have moving parts for switches and crossings. Hereat in comparison with the other options it is proven to be quite reliable and cost-effective. It was first implemented by Abt in 1886 at the Lugano Città–Stazione funicular (Switzerland). Since when the two rail system with the Abt turnout have grown quite popular so to become a standard for modern funiculars.
A few funiculars have been built using water tanks under the floor of each car that are filled or emptied until just sufficient imbalance is achieved to allow movement. The car at the top of the hill is loaded with water until it is heavier than the car at the bottom, causing it to descend the hill and pulling up the other car. The water is drained at the bottom, and the process repeats with the cars exchanging roles. The movement is controlled by a brakeman using the break handle of the rack and pinion system engaged with the rack mounted between the rails.
The Bom Jesus funicular built in 1882 near Braga, Portugal is one of the extant systems of this type. Another example, the funicular Neuveville - St-Pierre in Fribourg, Switzerland, which is of a particular interest as for counterbalancing it utilizes waste water, coming from a sewage plant at the upper part of the city.
Some of funiculars of this type were converted later on to electrical power. For example, the Giessbachbahn in the Swiss canton of Berne, opened in 1879, originally was powered by water ballast. In 1912 its energy provision was replaced by a hydraulic engine powered by a Pelton turbine. In 1948, it was replaced by an electric motor.
The cars can be attached to a second cable running through a pulley at the bottom of the incline in case the gravity force acting on the vehicles is too low to operate them on the slope. One of the pulleys must be designed as a tensioning wheel to avoid slack in the ropes. In this case, the winching can also be done at the lower end of the incline. This practice is used for funiculars with slopes below 6%, funiculars using sledges instead of cars, or any other case where it is not ensured that the descending car is always able to pull out the cable from the pulley in the station on the top of the incline. Another reason for a bottom cable is that the cable supporting the lower car at the extent of its travel will potentially weigh several tons, whereas that supporting the upper car weighs virtually nothing. The lower cable adds an equal amount of cable weight to the upper car while deducting the same weight from the lower, thereby keeping the cars in equilibrium.
A number of cable railway systems which pull their cars on inclined slopes were built since the 1820s. In the second half of the 19th century the design of a funicular as a transit system emerged. It was especially attractive in comparison with the other systems of the time as counterbalancing of the cars was deemed to be a cost-cutting solution.
The first line of the Funiculars of Lyon (Funiculaires de Lyon) opened in 1862, followed by other lines in 1878, 1891 and 1900. The Budapest Castle Hill Funicular was built in 1868–69, with the first test run on 23 October 1869. The oldest funicular railway operating in Britain dates from 1875 and is in Scarborough, North Yorkshire. In Istanbul, Turkey, the Tünel has been in continuous operation since 1875 and is both the first underground funicular and the second-oldest underground railway. It remained powered by a steam engine up until it was taken for renovation in 1968.
Until the end of the 1870s, the four-rail parallel-track funicular was the normal configuration. Carl Roman Abt developed the Abt Switch allowing the two-rail layout, which was used for the first time in 1879 when the Giessbach Funicular opened in Switzerland.
In the United States, the first funicular to use a two-rail layout was the Telegraph Hill Railroad in San Francisco, which was in operation from 1884 until 1886. The Mount Lowe Railway in Altadena, California, was the first mountain railway in the United States to use the three-rail layout. Three- and two-rail layouts considerably reduced the space required for building a funicular, reducing grading costs on mountain slopes and property costs for urban funiculars. These layouts enabled a funicular boom in the latter half of the 19th century.
In 1880 the funicular of Mount Vesuvius inspired the Italian popular song Funiculì, Funiculà. This funicular was destroyed repeatedly by volcanic eruptions and abandoned after the eruption of 1944.
An inclined elevator is not a funicular, since its cars operate independently on the slope, not in interconnected pairs.
Notably, Paris' Montmartre Funicular is today a funicular in name only. Its formal title is a vestige of its earlier configuration, namely when its two cars originally operated in a counterbalanced, interconnected pair, always moving in opposite directions in concert, thus meeting the definition of a funicular. The system now uses two independently operating cars that can each ascend or descend on demand, qualifying as a double inclined elevator, but retaining the term "funicular" in its title as a historical, albeit misleading, reference. 
The city of Valparaiso in Chile used to have up to 30 funicular elevators (Spanish: ascensores). The oldest of them is dating from 1883. 15 remain with almost half in operation, and others in various stages of restoration.
The Carmelit in Haifa, Israel, with six stations and a tunnel 1.8 km (1.1 mi) long, is claimed by the Guinness World Records as the "least extensive metro" in the world. Technically, it is an underground funicular.
- Cable car (railway)
- Gravity railroad
- Inclined elevator
- List of funicular railways
- Steep grade railway
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