The Transmission Gully project is a project to build a 27 kilometre four-lane (a minimum of two in each direction) motorway from Mackays Crossing to Linden (through Transmission Gully). There will be interchanges connecting the route to State Highway 58 and Kenepuru with a connection to Porirua CBD. In addition, there will be two link roads from the eastern Porirua suburbs of Whitby and Waitangirua to the route. The Porirua City Council is the Road Controlling Authority responsible for these link roads. The project entails extensive protection or relocation of utilities including the complete removal of transmission towers by Transpower from the northern section.