Public transport in Ireland exists in many of the Ireland's urban areas and rural areas, and takes a number of forms. Bus transport is the main form of public transport and is common in all cities. The cities, Dublin, Belfast, Cork, Derry, Limerick and Galway all have their own suburban rail networks, although Dublin is the only to have its own tram line, in the form of the Luas. Ireland has a population of 5 million people.