used in Gümmenen and Mühleberg Switzerland between 1918 and 1922 during the construction of the dam that retains Lake Wohlen. The trucks were built by Tribelhorn, and they used the Stoll system of current collection. United States Trolleytrucks have been used in mining operations and in road maintenance projects in the United States. Michigan From 1939 to 1964 the International Salt Company mine in River Rouge, Michigan used trolleytrucks that were converted Euclid models. This was an underground salt mine. Batteries were used to power the trucks when they strayed away from the overhead wires. For use within a mine the overhead wires may occasionally be relocated as excavation activity progresses. Hence the trolleytrucks used in mines do not necessarily have a travel route that is as fixed as the trolleytruck routes used in cities. California From 1956 to 1971 the Riverside Cement Company in Bloomington, California, operated Kenworth dump trucks converted to trolleytruck use at the Crestmore Quarry near Riverside, California. The trucks were equipped with "extension cords" for use of electric power near the shovel down in the mine. The long extension cords stored on powered reels aboard the trolleytrucks offered them increased mobility right at the load point. In 2014 Siemens announced the imminent start of a demonstration phase for an eHighway system in the area served by the Port of Los Angeles and Port of Long Beach. The announcement stated the eHighway would be a one-mile two-way stretch of road on the north- and south-bound sections of Alameda Street near where it intersects with Sepulveda Boulevard in Carson, California. The trucks have a second power source (diesel, compressed natural gas (CNG), or battery) so they can pull out from under the wires e.g. to pass a stopped vehicle, or when not using the eHighway. They are built by Mack Trucks in cooperation with Siemens. The demonstration phase is scheduled to last for one year. The initial announcement anticipated the trials would start in 2015; however, the system did not begin use until 2017 New Mexico The El Chino Mine near Santa Rita, New Mexico installed trolleytrucks in 1967. The trucks are equipped with diesel engines and the trolley power is used to assist the trucks up and down the ramp that leads into the mine. This type of double power arrangement is known as a trolley assist system. Nevada Barrick's Goldstrike mine, Nevada used trolleytrucks from