Ground-level power supply, also known as surface current collection or, in French, alimentation par le sol ("feeding via the ground"), is a concept and group of technologies whereby electric vehicles collect electric power at ground level from individually-powered segments instead of the more common overhead lines. Ground-level power supply has been used primarily for aesthetic reasons. During the late 2010s it has become more economical than overhead lines. Ground-level power supply systems date back to the beginning of electric tramways, with some of the earliest such systems using conduit current collection. Since the turn of the 21st century, new systems such as the Alstom APS, Ansaldo Tramwave, CAF ACR, Elways, and others have been introduced which use modern technology to address some of the limitations and dangers of the older systems, and supply power for buses, trucks, and electric cars. With the increased efficiency and energy density of capacitor and battery powered systems, ground-level power supply systems are used in smaller portions of the line to charge the batteries, for example only during station stops for buses and trains. Early systems Conduit current collection systems were implemented as early as 1881 with the Gross-Lichterfelde Tramway. The system is primarily composed of a channel, or conduit, excavated under the roadway; the conduit is positioned either between the running rails, much in the same fashion as the cable for cable cars, or underneath one of the rails; a car is connected to a "plow" that runs through the conduit and delivers power from two electric rails at the sides of the conduit to the car's electric motor. Plows were manually attached and detached from cars as they switched rail lines. Tram companies in Budapest trialed a conduit current collector system in 1887. Overhead lines were met with public opposition for aesthetic reasons, so the contractor Siemens-Halske implemented a concrete conduit underneath one of the trolley rails, with a narrow opening that allowed a "plow" to be inserted and make electrical contact with wires held by insulators at either side of the conduit. The system was used in several cities in Europe and the United States, where it was known as the "Budapest System". The system was generally safe, but tended to get clogged by mud and dirt. The system fell out of favor within a few years due to the cost of excavating the conduit, and was generally replaced with overhead lines.