A wartime invention converted to peace time needs is a mechanical road layer and it was in operation re-laying the road on Constitutional Hill , London , England . Brought here by the Americans in 1941 the machines were used to lay airfield runways quickly . One machine lays a 300 yard strip , 12 feet wide in two hours . Fed by a lorry acting as a hopper the machine moves at a slow walking pace and works at least twice as fast as men doing the same job . The actual machine used here was built in Britain for the Neuchatel Asphalte Company and cost about 瞿3000 . 2 October 1947