New Zealand's transport network comprises  of roads, including  of motorways, and  of railway lines. Most major cities and towns are linked by bus services, although the private car is the predominant mode of transport. The railways were privatised in 1993 but were re-nationalised by the government in stages between 2004 and 2008. The state-owned enterprise KiwiRail now operates the railways, with the exception of commuter services in Auckland and Wellington, which are operated by Transdev and Metlink, respectively. Railways run the length of the country, although most lines now carry freight rather than passengers. The road and rail networks in the two main islands are linked by roll-on/roll-off ferries between Wellington and Picton, operated by Interislander (part of KiwiRail) and Bluebridge. Most international visitors arrive via air, and New Zealand has six international airports, but  only the Auckland and Christchurch airports connect directly with countries other than Australia or Fiji.