 In 1940, the Centennial Highway developments saw the opening of a four-lane high-speed highway in Ngauranga Gorge bypassing the slower routes through Ngaio and Khandallah.During the 1950s, the high-speed Johnsonville–Porirua Motorway was built through Tawa on the eastern side of the valley.The first section from Johnsonville to the Tawa turnoff at Takapu Road at the southern entrance to Tawa opened on 15 December 1951, broadly following the line of the old North Island Main Trunk railway.