Stud contact systems were implemented from 1899 to 1921. Systems by the inventors Dolter and Diatto were used in Tours, Paris, and several towns in England. Power was supplied from studs set in the road at intervals, which connected to the traveling cars with contact shoes or contact skis. The studs were cylinders with their tops flush with the road surface. Underneath there was a switch mechanism that made an electrical connection with the top of the stud when a car with a strong electromagnet at its underside passed over it. The Diatto switches contained mercury, which often leaked or adhered to the side of the cylinder and kept the exposed top electrified. The Dolter switches used pivot arms, which tended to get stuck in the electrified position. Similar systems were operated by Thomson-Houston in Monaco from 1898 to 1903, and by František Křižík in Prague on the King Charles Bridge from 1903 to 1908. 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 posed maintenance issues and road safety issues. The Bordeaux conduit system remained the last in operation until being decommissioned in 1958. For 40 years, these systems were not reintroduced because they didn't meet modern safety standards. Modern systems A number of ground-level power supply systems were developed from the 1970s through the 1990s, but failed to reach commercialization due to reliability and safety issues. The first ground-level power supply system developed to modern safety standards was the Ansaldo Stream. After a competing system, Alstom APS, became the first commercially implemented system in 2003, there has been a proliferation of commercial implementations of ground-level power supply systems. During the late 2010s, ground-level power supply systems have become more cost-effective than overhead line systems. Electric road systems 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. Both systems were found to be more economical than the tested overhead line system and dynamic inductive charging system. The in-road rail system is planned to deliver up to 800 kW per vehicle traveling over a powered segment of the rail, and the system is