thumb|right|[[MetroCentro (Seville)|Seville Tram equipped with CAF ACR ground-level power supply, 2019]]
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 that enable electric vehicles to collect electric power at ground level instead of the more common overhead lines.
Ground-level power supply systems date to the beginning of electric tramways. Often they were implemented where the public expressed an aesthetic desire to avoid overhead lines. Some of the earliest systems used conduit current collection. Systems in the 21st century, such as Alstom APS, Ansaldo Tramwave, CAF ACR, and Elways, were developed to modern standards of safety and reliability, and added the ability to supply power to electric buses, trucks, and cars.
Some ground-level power supply systems use efficient, energy-dense capacitors and batteries to power portions of an electric transit system—for example, enabling buses and trains to charge their batteries during station stops.
Early systems
thumb|Conduit for current collection between the rails of [[streetcars in Washington, D.C., 1939. First installed in 1895, it remained in operation until 1962.]]
thumb|right|Remaining conduit tram track on the ramp to the abandoned [[Kingsway tram subway in London, 2011, with plants growing in the conduit]]
Conduit current collection systems were implemented as early as 1881 with the Gross-Lichterfelde Tramway.
Cleveland opened a conduit line in 1885. Washington, D.C. installed its first conduit current collection system in 1895. By 1899 all downtown lines were converted to the conduit system, which remained in operation until 1962. Stud contact systems were short-lived due to safety issues.
Conduit current collection systems were used in several major cities, including Monaco, Dresden, Prague, Tours, Washington, and London, but were not reliable or safe enough for commercial use.
The first ground-level power supply system developed to modern safety standards was the Ansaldo Stream,
Advancements in technology in the late 2010s led to ground-level power supplies seeing increasing reliability and economic feasibility.
Electric road systems
Sweden
thumb|right|Electric truck driving on a public road with Elways-Evias ground-level power supply, near [[Stockholm Arlanda Airport, 2019]]
Electric roads power and charge electric vehicles while driving. Sweden has tested electric road systems that charge the batteries of trucks and electric cars, and among the tested systems are two ground-level power supply systems tested since 2017, in-road rail by Elways-Evias and on-road rail by Elonroad. Elonroad later developed an in-road rail system for highway use at speeds up to . The rails have been tested while submerged in salt water and were found to be safe for pedestrians.
France
The co-director for one of the French Ministry of Ecology working groups on electric road systems stated that rail-based ERS are the most advantageous, though the specific rail technology has yet to be standardized. France plans to invest 30 to 40 billion euro by 2035 in an electric road system spanning 8,800 kilometers. Ground-level power supply technologies are considered the most likely candidates for electric roads. Two projects for assessment of electric road technologies have been announced in 2023. The first French public road with an electric road system is planned to open in 2024 using a ground-level power supply system derived from Alstom APS.
Standardization
Alstom, Elonroad, and other companies have, in 2020, begun drafting a standard for ground-level power supply electric roads. The European Commission published in 2021 a request for regulation and standardization of electric road systems. Shortly afterward, a working group of the French Ministry of Ecology recommended adopting a European electric road standard formulated with Sweden, Germany, Italy, the Netherlands, Spain, Poland, and others.
A standard for on-board electrical equipment for a vehicle powered by a rail electric road system (ERS) was approved and published in late 2022. The standard, CENELEC Technical Standard 50717, specifies the following: an ERS voltage of 750 volts; a contact shoe capable of withstanding impact of gravel and similar road debris at the maximum operating speed; a weak link that breaks off the current collector at the structural fixing points if the force is larger than the maximum specified by the vehicle manufacturer; automatic monitoring of the presence of ERS infrastructure; automatic engagement and disengagement; a presence signal that may be analog or digital, and optional standard bidirectional communication; ease of inspection and replacement for the wearing parts of the sliding contact; and standard tests, markings, maintenance, and operational environment conditions. The 50717 standard does not encompass, but specifies for normative purposes, three architectures for ERS infrastructure: Type A architecture with two parallel surface-level conductive rails, one positive and one negative; Type B architecture with a single surface-level or raised track with short segments where each two segments in series consist of one positive and one negative segment; and Type C architecture with three parallel conductive rails, one positive and one negative below surface level in 1.5 cm wide channels, and one or more rails earthed at surface level. in accordance with European Union directive 2023/1804 is specified in CENELEC technical standard 50740. The standard was approved in 2025.
Modern implementations
Ansaldo Stream
The first modern ground-level power supply system to be developed is the Ansaldo Stream system. STREAM is an acronym that stands for "Sistema di TRasporto Elettrico ad Attrazione Magnetica", meaning "System of Electric Transport by Magnetic Attraction". The system uses a channel in the road made of insulating composite fiberglass material which contains a flexible copper strip; a vehicle passing over the channel with a special magnetic contact shoe raises the conductor to the surface, allowing power to flow to the vehicle. Segments of the strip are powered only when a vehicle passes over them. The system was developed in 1994 and trialed on a public tram line in 1998,
Alstom APS
thumb|right|[[CBD and South East Light Rail|Light rail at the Queen Victoria Building, Sydney in 2019. Vehicles and pedestrians may safely move across the electrified rail because segments are powered only when there is a compatible vehicle covering them.]]
Alstom APS uses a third rail placed between the running rails, divided electrically into 11-metre segments. These segments automatically switch on by radio control only when a tram is passing over them, thereby avoiding any risk to other road users. The tram has two collector shoes, and two segments of rail are active at any given time, to avoid interruption of power when passing between segments.
APS was developed by Innorail, a Spie Enertrans subsidiary acquired by Alstom. It was created for the Bordeaux tramway, which was built from 2000 to 2003. Since 2011, other cities have used the technology. The French government reports no electrocutions or electrification accidents on any tramway in France from 2003 through 2022.
Alstom is modifying the APS system for use by electric road vehicles, such as buses, trucks, utility vehicles, and cars. The system is expected to supply 500kW to vehicles moving at up to . As of 2024, the system had been tested for safety when the road is cleared by snowplows, under exposure to snow, ice, salting, and saturated brine, and for skid and road adherence safety for vehicles, including motorcycles.
CAF ACR
thumb|CAF ACR tram, [[Luxemburg, 2021. The tram is powered between stations by supercapacitors charged from the two metal strips between the rails at station stops.]]
Construcciones y Auxiliar de Ferrocarriles (CAF) trialed its Acumulador de Carga Rápida (ACR) system in 2007 in Seville. The system is capable of charging from strips on the ground or from overhead wires. Sections of the Seville MetroCentro tramway around the Seville Cathedral were converted to the ACR ground-level power supply system. ACR's first commercial installation was aboard Urbos trams supplied to MetroCentro in 2011, allowing the permanent removal of overhead lines around the cathedral.
Line 1 of the Tranvía de Zaragoza has also used ACR since its second construction phase was completed in 2013. The use of ACR avoided the installation of overhead lines in the city's historic centre.
ACR was included in the Newcastle Light Rail in Australia and Luxembourg's new tram system.
Ansaldo Tramwave
Derived from Ansaldo Stream and developed by Italian company Ansaldo STS (which later became Hitachi Rail STS), the Ansaldo TramWave ground-level power supply system successfully entered commercial application in 2017, with the opening of Zhuhai tram Line 1 first phase in China. The tram is the first fully low-floor tram system adopting ground level power supply technology. Later in 2017, Western Suburb Line in Beijing was opened with the same technology from Ansaldo. The technology has been licensed to CRRC Dalian and all the technologies were transferred to China.
In 2019, Zhuhai City evaluated whether to dismantle the tram line, after 3 years of operation. As of 2024, CRRC Dalian opposes dismantling, proposing to restart operation.