 An intersection between SH1 and Mungavin Avenue remained at Porirua until 1989 when the intersection was replaced with a grade-separated roundabout interchange with State Highway 1 passing under the interchange.Porirua City had a population of 56,559 at the 2018 New Zealand census, an increase of 4,842 people (9.4%) since the 2013 census, and an increase of 8,013 people (16.5%) since the 2006 census.There were 17,838 households.