Transport in Auckland, New Zealand's largest city, is defined by factors that include the shape of the Auckland isthmus (with its harbours creating chokepoints and long distances for land transport), the suburban character of much of the urban area, a history (since World War II) of focusing investment on roading projects rather than public transport, and high car-ownership rates. These factors have contributed to a transport system that is highly dependent on private motor vehicles. Several motorways radiating to the north, northwest, southwest and south act as the backbone of the city's road network, with the busiest section of motorway carrying over 200,000 vehicles a day. The use of public transport in Auckland was high until the 1950s but subsequently declined during the second half of the 20th century, before experiencing a strong resurgence from the early 2000s. With the motorway network now largely completed, major efforts are underway to increase public transport use to address Auckland's congestion. Recent efforts have also focused on making cycling a safer and more attractive transport option. Auckland has New Zealand's largest commercial port (mostly used for international commerce) and the country's largest international airport. It also has the Southern Hemisphere's largest marina. History Pre-European period Throughout Auckland's pre-European period, its strategic location on the Waitematā and Manukau harbours had important transport implications. Māori hauled waka (canoes) between the harbours at portages, short traversable sections of land that connected the bodies of water. Some of the most major portages were Te Tō Waka, the shortest portage located at Ōtāhuhu, Te Tōanga Waka (the Whau River portage), as well as Te Pai o Kaiwaka, the Waiuku portage which connected the Manukau Harbour to the Waikato River in the south, and Te Tōangaroa in the north-west, connecting the Waitematā and Kaipara harbours overland at Kumeū. 19th and early 20th century As a port city, Auckland's initial (19th century) urban growth occurred in an intense fashion, concentrated around the harbour in a similar manner to most other mercantile cities, with lack of transportation options limiting development to locations within walking distance of each other. The overcrowding of the inner city eventually created a demand for expansion made viable when new transportation technology appeared around 1900 in the form of streetcars (trams) and railways arriving in Auckland. Auckland's first tram line, from the CBD to Ponsonby via Karangahape Road, opened on 24 November 1902. As the system grew,