While trams and railway lines shaped Auckland's rapid extension in the early first half of the 20th century, they were soon overtaken by motor vehicles, with Auckland boasting one of the highest car-ownership rates of the world even before World War II. Their growing popularity meant that urban development was freed from narrow corridors, and could occur anywhere new roads were built, leading to a rapid decentralisation, with urban growth spreading all over the isthmus. In 1959 the new Auckland Harbour Bridge linked North Shore with the city, further extending its reach.