 After the Ennis Avenue turnoff which takes Highway 1 with it, Patterson Road becomes State Route 18 and goes through the Rockingham Beach area until it turns into Railway Terrace one block from the ocean at Mangles Bay, which is part of the Indian Ocean.Until the Kwinana Freeway was built to Safety Bay Road in 2002, Patterson Road was the main road to Mandurah and the South West of Western Australia from Perth.The Freeway construction has relieved pressure on the road.