The first completed tunnel tube, for northbound traffic, was eventually opened by Queen Elizabeth II on 3 July 1963, with the southbound tunnel opening in March 1964. The total cost of the project was £10 million. By this point, the migration of port facilities downstream to the deeper waters of the Firth of Clyde and improvements in engineering technology had allowed the consideration of bridges downstream of the city centre, namely the Kingston Bridge and, much further downstream than the Tunnel, the Erskine Bridge.