Speed limits in Australia range from 5 kilometres per hour (3.1 mph) shared zones to 130 kilometres per hour (81 mph). In the Northern Territory four highways have 130 kilometres per hour (81 mph) zones. Speed limit signage is in km/h since metrication on 1 July 1974. All speed limits (with the sole exception of the South Australian school and roadworks zones which are signposted at 25 km/h) are multiples of 10 km/h – the last digit in all speed signs is zero. Speed limits are set by state and territory legislation albeit with co-ordination and discussion between governments.