The Sydney Harbour Bridge construction started in 1924 and took 1400 men eight years to build at a cost of £4.2 million. Six million hand driven rivets and 53,000 tonnes of steel were used in its construction. It now carries eight traffic lanes and two rail lines, one in each direction, but at the time of its construction the two eastern lanes were tram tracks. They were converted to road traffic when Sydney closed down its tram system in the 1950s.