 A more detailed plan of a rapid transit system was worked on, and a planning committee known as Auckland Rapid Transit was formed.The scheme design as finalised in 1972 had a tight inner city underground ring, operating in one direction only.The existing suburban rail line routes were to be used with track duplication to avoid freight conflicts, with extensions to Hobsonville and Howick and two new lines; under the harbour to Whangaparaoa and south to the Airport.