 As part of metrication in 1974, speed limits and speed advisories were converted into kilometres per hour, rounded to the nearest 10 km/h, leading to small discrepancies in speed limits.Signage changed from a North American-style black and white textual sign to a design based on metric signage in use in New Zealand with black number in red annulus (or circle) on white, itself a derivative of the European standard number in red circle design.The urban default, which prior to the 1930s was , applied to any "built up area", usually defined by the presence of street lighting.