In 2010 the state government added commissioner of Main Roads Western Australia and director-general of the department to his roles, giving him responsibility for all three of the major transport bodies.
Mr Waldock will leave all three roles at the end of his current term on July 29.
Also leaving is Main Roads chief executive Stephen Troughton, who takes up the role of Transport for NSW’s deputy secretary, infrastructure services in July.
Mr Conran had held the position since 2008.
WA Child and Adolescent Health Service executive director, commissioning Tina Chinery has resigned from her position in order to take up the job of chief operating officer for the Cairns and Hinterland Health Service.