During the early 20th century, the canal network was in decline because of increasing competition from the railways and road transport. Until the 1950s, freight and other cargo was still carried on the canals, by then owned by the railway companies. When the railways were nationalised in 1948, the canals they owned were also incorporated into the new British Transport Commission. The Commission focused on encouraging commercial traffic to the waterways, but with the construction of motorways in the 1950s, and legislation such as the Clean Air Act 1956 affecting the coal carriers using the waterways, that policy could not be sustained. The last regular long-distance narrow-boat-carrying contract, to a jam factory near London, ended in October 1970, although lime juice continued to be carried by narrow boat from Brentford to Boxmoor until 1981, and aggregate from Thurmaston to Syston from 1976 until 1988.