Simply speaking, Cable-Propelled Transit (CPT) is a transit technology that moves people in motor-less, engine-less vehicles that are propelled by a steel cable.
There are two Cable Propelled Transit types: top supported and bottom supported.
Top supported systems, also known as aerial cable systems, are supported from above via a cable (which may or may not be the same cable that propels the cabins — this varies by technology.) Aerial cable technologies include:
Bottom supported systems are supported by tracks or rails underneath, yet are still propelled by a cable. Bottom supported cable technologies include:
The support describes the guideway along which a vehicle travels. Support can either by provided by rails or cables. In all but the rarest of examples, support from above is provided by cable and support from below is provided by rails.
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Unlike traditional vehicles, CPT vehicles do not have an onboard engine or motor. Propulsion is provided by an off-board engine that moves a cable. Vehicles are equipped with a grip used to attach and detach the vehicle to the cable.
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Grips are what attaches a vehicle to a cable. There are two major types of grips and cable technology can be subdivided into two categories based on those types: detachable and fixed.
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Tower sizes and footprints are dependent on cable technology choice, system capacity and tower span distances.
Lighter-weight systems, such as the MDG, typically have smaller, cylindrical towers while heftier systems, such as the 3S, have larger, lattice-style towers. In general, larger tower sizes are correlated to longer tower span distances and larger system capacities.
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Every modern day CPT cable is made of steel, and configured in a loop. This is done by "splicing" the cable. The most basic cable system operates on one single cable loop, while others have multiple loops as well as several stationary cable lines.
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Gondolas (MDG, BDG, 3S, pulsed) can turn corners in various ways, depending on the technology in use, the degree of the turn, and the alignment. Most often, a standard turn would occur in a station where two cable loops would meet at an angle and cabins would seamlessly move from one to the next.
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The first documentation of cable dates back to 250 BC. For hundreds of years, rope propelled transit was used to move people and goods, such as minerals and ores.
Major cable innovations occurred in the 1800s with such inventions as the steel cable and the detachable grip. During this time period, cable was largely used for industrial purposes.
Cable was first adapted for human transit in the form of cable cars, with cities such as San Francisco and Chicago pioneering this mode. As transit technology shifted to electric power, these systems became largely obsolete. At this point, around the 1930s and 40s, cable, for the movement of people, shifted to the recreational market, where it continued to grow and innovate until the last few decades.
While the use of cable does not ever fully shift from one market to the next (it is still used for industry and recreation) in the recent years there has been a noticeable growth of the technology within the urban market.
CC images / photo credits (links): Top Supported, Bottom Supported, Support, Propulsion, Grips, Towers, The Cable, Cornering, and Cable Evolution.