The period of nationalisation saw sweeping changes in the national railway network. A process of dieselisation and electrification took place, and by 1968 steam locomotion had almost been entirely replaced by diesel and electric traction. Passengers replaced freight as the main source of business, and one third of the network was closed by the Beeching Axe of the 1960s in an effort to reduce rail subsidies. This in effect was the beginning of a downward spiral of the once pioneering British railway system, as for the first time since the very beginning it was no longer looking to expand. Britain's motorways had began construction, and cars had finally started to take over from trains as the publics first choice for travel.