the conduit current collection system, where the power supply is carried in a channel or vault under the roadway. This is a tube, open at the top to allow a blade to enter and extend slippers against the power conductors, which are either side of the access opening slot, near the top of the channel. The arrangement is shaped so that live surfaces can not be reached by hand, and the lower part of the conduit provides drainage to remove any water. Conduit power was first designed in the steam age (c.1900) when power was transmitted mechanically from a series of steam-powered rotating screws, as shown in the illustration (left) also published by Harmsworth Popular Science. A more recent roadway power supply design used by the Bordeaux tramway involves alternate (line and neutral) panels which are only powered whilst they are actually under the tram. This system is called APS (French: Alimentation par Sol which implies sub-surface power feed in English). Overhead electrical net A parking area with an overhead electrical net was in use at Seoul Grand Park Zoo in South Korea, to recharge electric vehicles , This was similar to a fairground bumper car arrangement which allowed vehicle batteries to be recharged, prior to introduction of the more modern OLEV Online Electric Vehicle system. The advantage was that vehicles could be parked randomly, as convenient, and there was no need for either the tripping hazard of trailing cables used by most electric vehicles nor for fiddly precise alignment of conductor poles needed by trolley buses. Linear Motor Propulsion An alternative form of electro-magnetic coupling is called a linear motor, first developed by Professor Eric Laithwaite at Imperial College London in the 1960s. Instead of supplying electric motors with power directly or charging on-board batteries, the RPEV is fitted with magnets which are impelled horizontally in the same way as the rotor on an ordinary electric motor is impelled to rotate. A linear motor works in exactly the same way a round motor which has been split to its centre, laid flat and extended. The Shanghai Transrapid and Bombardier Advanced Rapid Transit systems are practical examples of this type of RPEV technology applied to rail transport systems (which are sometimes called railroads, especially in USA). Maglev uses magnetic repulsion to support the carriage weight as well as to propel the vehicle forward, so wheels are not needed. Maglev trains