Speed limits in Australia
Speed limits in Australia range from shared zones to. In the Northern Territory four highways have zones. Speed limit signage is in km/h since metrication on 1 July 1974. All speed limits 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.
Common limits
Australian states and territories use two "default" speed limits. These apply automatically in the absence of 'posted' speed restriction signage. The two default speed limits are:- within built-up areas,, except for the Northern Territory which remains at
- outside built-up areas, ; two exceptions are Western Australia and the Northern Territory at
- Shared zones are.
- School zones are variable speed zones, with a limit applying during gazetted school terms and at specific times of the day when children are expected to be present. In South Australia, the limit is. A minority of school zones have flashing lights to indicate when the lower speed limit applies.
- 40 km/h zones. A number of local governments have implemented lower speed limits, typically 40 km/h, in certain areas, such as shopping precincts, whole suburbs such as Balmain and Rozelle in Sydney, or areas with high pedestrian activity.
- Many sub-arterial roads are zoned.
- Major connector roads and smaller highways are zoned,, or.
- Some highways and freeways are zoned.
- Most of the Stuart, Arnhem, Barkly and Victoria highways in the Northern Territory are zoned.
Speed limits are enforced in all areas of the country. Tolerance ranges from 3% to 10% in most states but only 3 km/h in Victoria, an issue that has caused much controversy in that state, especially in light of the fact that earlier Australian Design Rules specified that vehicle speedometers may have up to 10% leeway in accuracy. This was updated in 2006 to require that the "speed indicated shall not be less than the true speed of the vehicle." Detection measures used are radar, LIDAR, fixed and mobile speed cameras, Vascar, pacing and aircraft.
Default speed limits by state and territory
Despite introduction of model national road rules by the states in 1999, Western Australia and the Northern Territory retain different default speed limits. The table below indicates the default speed limits along with typical school zone limits and the highest zone in each locality.In the external territories, and in some special cases, the speed limits may differ significantly from those found across the rest of the nation.
| State / territory | School zone | Built-up area | Rural area | Highest speed zone |
| Australian Road Rules | number on school zone sign | 50 | 100 | number on speed-limit sign |
| Australian Capital Territory | 40 | 50 | 100 | 100 |
| New South Wales | 40 on all roads 40 km/h or more 30 in designated 30 km/h zones in Manly and Liverpool | 50 | 100 | 110 |
| Northern Territory | 40 | 60 | 110 | 130 |
| Queensland | 40 on roads 70 km/h or less 60 on roads 80 km/h and some 90/100 km/h 80 on roads 110 km/h and some 90/100 km/h | 50 | 100 | 110 |
| South Australia | 25 on roads 60 km/h or less | 50 | 100 | 110 |
| Tasmania | 40 on roads 70 km/h or less 60 on roads 80 km/h or more | 50 | 100 | 110 |
| Victoria | 40 on roads 70 km/h or less 60 on roads 80 km/h or more | 50 | 100 | 110 |
| Western Australia | 40 on roads 70 km/h or less 60 on roads with 80 km/h or 90 km/h | 50 | 110 | 110 |
| External territories | ||||
| Christmas Island | 40 | 40 | 90 | 90 |
| Cocos Islands | -- | 30 | 50 | 50 |
| Norfolk Island | 30 | 30 - Kingston Foreshore 40 - Burnt Pine Central Business District | 30 - Norfolk Island National Park 50 - Other Areas | 50 |
| Special cases | ||||
| Lord Howe Island | -- | -- | -- | 25 |
Signage
Historical limits
Historically, Australia operated a simple speed limit system of urban and rural default limits, denoted in miles per hour. 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 on white, itself a derivative of the European standard number in red circle design.Urban limits
The urban default, which prior to the 1930s was, applied to any "built up area", usually defined by the presence of street lighting. This limit was progressively increased to over the next 30 years by each of the states and territories, with New South Wales being the last to change in May 1964. South Australia adopted on 30 November 1950 along with the "new short-right hand turn".Metrication led to the default urban limits of being converted to 60 km/h, an increase of.
In the late 1990s and early 2000s, the urban default limit was progressively lowered to nationally for reasons of road, and especially pedestrian, safety. However, many existing roads, especially subarterial roads in urban areas, have had limits posted on them. Queensland's Manual of Uniform Traffic Control Devices states that is the general minimum speed limit for traffic-carrying roads. The Northern Territory has retained the limit; however, is also a common speed limit.
Rural limits
Outside of built up areas, a prima facie speed limit applied. In New South Wales and Victoria, speed limit was 50 miles per hour. In the 1970s however, most state speed limits were gradually replaced by absolute limits. An absolute speed limit of was introduced to Victoria in 1971, as a trial. This was subsequently reduced to in late 1973. South Australia introduced an absolute speed limit of in 1974.With metrication in 1974, the rural defaults of and became and respectively. The 50 mph limit in New South Wales became a limit of 80 km/h.
New South Wales introduced an absolute speed limit of in 1979, replacing the limit of The Northern Territory introduced an absolute speed limit of in 2007, along with zones on the Territory's four major highways.
NT open speed limits
The Northern Territory had no blanket speed limits outside major towns until January 2007, when a general rural speed limit of was introduced, although four major highways had higher zones. Speed-limit advocates note that the per-capita fatality rate in 2006 was the highest in the OECD and twice the Australian average. In 2009, the opposition unsuccessfully sought the removal of the limits on three out of the four highways where it applied, arguing that total fatalities in the Northern Territory had increased significantly during the first two years of the speed limit. In argument against the motion, the government provided more detailed statistics than normally published; these statistics showed a reduction in fatalities along the highways where limits were introduced. In 2011 the opposition argued for a return to "open speed limits". For the 2012 election the Country Liberals' transport policy promised an evidence-based approach. After winning government, de-restriction of Stuart Highway was proposed; a planned 12-month de-restriction was initiated on 1 February 2014. The trial on of Stuart Highway was expanded later in the year to another, and continued indefinitely in January 2015 during a review of the initial results since "in the first 11 months, there were no recorded fatalities." From September 2015, a stretch of Stuart Highway between Barrow Creek and Alice Springs had speed limits removed for a 12-month trial. speed limits were restored on 20 November 2016 due to the electoral loss of the Country Liberal Party.
Derestriction signs in NSW
Often the start of rural default 'limits' or prima facie allowances were signalled by use of the speed derestriction sign, catalogued R4-2 in AS1742.4. . The speed derestriction sign had developed 'different meaning' over time at state and territory level, although its contract-meaning under "The United Nations Convention on Road Traffic, Signs & Signals" where the sign is catalogued "C,17a", is; "End of all local prohibitions imposed on moving vehicles" and has never changed. In the Northern Territory, they designated the end of speed restrictions. In Victoria and Western Australia they meant that the rural default speed limit applied, whilst in New South Wales, they indicated that the prima facie limit applied.New South Wales's prima facie limit, often signed by derestriction signs, was only enforced in cases where a driver's speed could be demonstrated to be excessive or dangerous in the context of prevailing road conditions. This was somewhat similar in principle to "reasonable and prudent" limits in other jurisdictions. This led to the widespread but misleading belief that no limit applied, and that derestriction signs indicated an "unlimited" limit. This belief, coupled with repeated studies showing 85th percentile speeds in excess of on major routes, comparatively high road tolls, difficulty in prosecuting speeding offences, and the variance in meaning of the derestriction sign across states, led New South Wales to harmonise its rural default limit to in 1978. The use of derestriction signs in New South Wales was officially discouraged, and on state controlled routes, signs were progressively used instead.