Advisory speed limit

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A U.S. advisory speed limit sign, warning drivers of a curve ahead. Advisory Curve Speed English 45.svg
A U.S. advisory speed limit sign, warning drivers of a curve ahead.

An advisory speed limit is a speed recommendation by a governing body, used when it may be non-obvious to the driver that the safe speed is below the legal speed. It is a posting which either approximates the Basic Speed Law or rule (and is subject to enforcement as such) or is based on a maximum g-force exerted at a specific speed. Advisory speed limits are often set in areas with many pedestrians, such as in city centers and outside schools, and on difficult stretches of roads, such as on tight corners or through roadworks. While travelling above the advisory speed limit is not illegal per se, it may be negligence per se and liability for any collisions that occur as a result of traveling above the limit can be placed partially or entirely on the person exceeding the advisory speed limit.


Signposting of advisory speed limits varies from country to country; Australia makes extensive use of advisory speed limits across its highway networks while the Richtgeschwindigkeit ("reference speed") in Germany is valid for the whole autobahn network (but can be overruled by speed limits in particular sections or for special reasons like weather conditions or roadworks), while the United States and the United Kingdom only give advisory speed limits for hazards such as bends.


Use of advisory speed limits varies by locale, but they are generally used to reduce speed along short stretches of dangerous road, such as on the tight curves of an off-ramp or on a busy shopping street. The advisory speed limit when not posted is generally the same as the mandatory speed limit in ideal conditions.


In Australia, if a person is involved in a single vehicle accident and the resulting investigation reveals that the driver was exceeding the Advisory Speed Limit displayed it can be a breach of the Insurance Cover Contract, resulting in no payout.

Advisory speeds in corners are set out in AS (Australian Standard) 1742.2-2009 Manual of Uniform Traffic Control Devices, Part 2, appendix F. [1] Corners are signed to indicate a speed at which lateral g-forces will not exceed 0.22g to fall well within the minimum suggested static rollover threshold of 0.35g for non-dangerous goods. [2]


Zeichen 380-52 - Richtgeschwindigkeit 80 km-h, StVO 1992.svg
Zeichen 381-52 - Ende der Richtgeschwindigkeit 80 km-h, StVO 1992.svg
Now abolished German signs (in km/h) indicating the beginning and end of an advisory speed limit.

The Richtgeschwindigkeit (German Advisory or Suggested Speed of Travel) is a legal term in Germany describing the advisory speed limit for roads without a mandatory speed limit. Autobahns have an advisory speed limit of 130 kilometres per hour (81 mph) on non-signposted sections.

Exceeding the advised speed is not a criminal offense, but may result in greater liability in the case of a collision due to an increased danger of operating the vehicle. [3]

In Germany, the Autobahn-Richtgeschwindigkeits-Verordnung (Directive on Reference Speed on Motorways), introduced in 1974, recommends a speed of no more than 130 km/h (81 mph) for autobahns and similar roads, whose lanes are separated by a median or which have at least two lanes per direction, provided there are no traffic signs posting a lower speed limit.

Until 31 August 2009, a different reference speed could be posted by the traffic signs number 380 and 381, according to §42 of the German traffic code (Straßenverkehrsordnung, StVO), as seen above. As these traffic signs were only rarely used, they have been abolished, and will be fully removed by 31 October 2022.

New Zealand

Advisory speeds are not legal speed limits. [4] Advisory speeds end in 5 to avoid confusion with mandatory speed limits which end in 0. The limits are established at 0.22g lateral g-force [5] to fall well within the minimum static rollover threshold of 0.35g. [6]

United Kingdom

In the United Kingdom, most speed limits imposed by variable-message signs are advisory, and there are no sanctions for drivers who exceed them; a notable exception being the Gatsometer-camera enforced, MIDAS and ATM variable limits on motorways such as the M25, M42 and M6. [7] Crucially, the signs imposing these limits are distinct from regular, advisory VMS displays by the inclusion of a red ring surround, effectively changing them from advance hazard warnings into standard, mandatory speed-limit signs.

As local councils require consent from the Department for Transport before changing speed limits, some use advisory speed limits on roads that the DfT refuses to officially downgrade. [8]

The usefulness of advisory speed limits has been questioned by a number of studies: one group from the Transportation Research Board found advisory speed limits through roadworks being consistently flouted by motorists, [9] while an investigation by Manchester Evening News found that almost all buses in Manchester city centre exceeded the local 10 miles per hour (16 km/h) advisory speed limit; some by as much as 30 miles per hour (48 km/h). [10]


The signage for advisory speed limits is not defined by the Vienna Convention on Road Signs and Signals, and is therefore not standardised internationally. The United States uses a small yellow sign under the main warning sign, as well as a standalone variation on the standard speed limit sign, with a yellow background instead of a white one, the words "speed limit" omitted and an additional panel stating the type of hazard ahead. Though they list speeds, the United States advisory speed signs are classified as warning signs, not regulatory signs, as primary speed signs are. [11] Australia uses a similar design as the United States in spite of regulatory speed limit signs being quite different. Germany used a square sign with a blue background and white lettering, similar to the minimum speed limit sign, [3] and New Zealand uses a yellow background with black lettering (similar to the Australian design without the "km/h" lettering). The United Kingdom currently uses an oblong white rectangle with black lettering stating "Max Speed".

Related Research Articles

Speed limit Maximum legal speed of vehicles

Speed limits are used in most countries to set the legal maximum speed at which vehicles may travel on a given stretch of road. Speed limits are generally indicated on a traffic sign reflecting the maximum permitted expressed as kilometres per hour (km/h) and/or miles per hour (mph). Speed limits are commonly set by the legislative bodies of national or provincial governments and enforced by national or regional police and judicial authorities. Speed limits may also be variable, or in some places nonexistent, such as on most of the Autobahn in Germany.

Traffic sign Signboard displaying information for road users

Traffic signs or road signs are signs erected at the side of or above roads to give instructions or provide information to road users. The earliest signs were simple wooden or stone milestones. Later, signs with directional arms were introduced, for example the fingerposts in the United Kingdom and their wooden counterparts in Saxony.

Variable-message sign Electronic traffic sign with changeable messages

A variable-message sign, often abbreviated VMS, CMS, or DMS, and in the UK known as a matrix sign, is an electronic traffic sign often used on roadways to give travelers information about special events. Such signs warn of traffic congestion, accidents, incidents such as terrorist attacks, AMBER/Silver/Blue Alerts, roadwork zones, or speed limits on a specific highway segment. In urban areas, VMS are used within parking guidance and information systems to guide drivers to available car parking spaces. They may also ask vehicles to take alternative routes, limit travel speed, warn of duration and location of the incidents, inform of the traffic conditions, or display general public safety messages.

Warning sign Sign that warns people about something.

A warning sign is a type of sign which indicates a potential hazard, obstacle, or condition requiring special attention. Some are traffic signs that indicate hazards on roads that may not be readily apparent to a driver.

Dual carriageway Type of road

A dual carriageway or divided highway is a class of highway with carriageways for traffic travelling in opposite directions separated by a central reservation. Roads with two or more carriageways which are designed to higher standards with controlled access are generally classed as motorways, freeways, etc., rather than dual carriageways.

Autobahn National expressway in Germany

The Autobahn is the federal controlled-access highway system in Germany. The official German term is Bundesautobahn, which translates as 'federal motorway'. The literal meaning of the word Bundesautobahn is 'Federal Auto(mobile) Track'.

Road signs in the United Kingdom Overview of road signs in the United Kingdom

Road signs in the United Kingdom and in its associated Crown dependencies and overseas territories conform broadly to European design norms, though a number of signs are unique: direction signs omit European route numbers and road signs generally use the Imperial System of units, unlike the rest of Europe.

Road signs in Sweden are regulated in Vägmärkesförordningen, VMF (2007:90), and are to be placed 2 metres from the road with the sign 1.6 m from the base for motorized roads. Except for route numbers, there are a maximum of three signs on a pole, with the most important sign at the top. All signs have a reflective layer added on selected parts of the sign as is custom in European countries; most larger signs also have their own illumination.

Road signs in Singapore closely follow those laid down in the traffic sign regulations used in the United Kingdom, although a number of changes over the years have introduced some slight deviations that suit local road conditions. Road signs in Singapore conform to the local Highway Code under the authority of the Singapore Traffic Police.


Bundesstraße, abbreviated B, is the denotation for German and Austrian national highways.

Road signs in Italy Overview of road signs in Italy

Road signs in Italy conform to the general pattern of those used in most other European countries, with the notable exception that the background of motorway (autostrada) signs is green and those for 'normal' roads is blue. They are regulated by the Codice della Strada and by the Regolamento di Attuazione del Codice della Strada in conformity with the Vienna Convention on Road Signs and Signals.

Road signs in Thailand Overview of road signs in Thailand

Road signs in Thailand are standardized road signs similar to those used in other nations but with certain differences. Until the early 1980s, Thailand closely followed US, Australian, and Japanese practices in road sign design, with diamond-shaped warning signs and circular restrictive signs to regulate traffic. Signs usually use the FHWA Series fonts typeface also used in the United States.

Road signs in the United States Road / traffic signs utilized in the United States

In the United States, road signs are, for the most part, standardized by federal regulations, most notably in the Manual on Uniform Traffic Control Devices (MUTCD) and its companion volume the Standard Highway Signs (SHS).

Road signs in South Korea are regulated by the Korean Road Traffic Authority.

Speed limits in Germany Overview of speed limits in Germany

Speed limits in Germany are set by the federal government. All limits are multiples of 10 km/h. There are two default speed limits: 50 km/h (31 mph) inside built-up areas and 100 km/h (62 mph) outside built-up areas. While parts of the autobahns and many other freeway-style highways have posted limits up to 130 km/h (81 mph) based on accident experience, congestion and other factors, many rural sections have no general speed limit. The German Highway Code (Straßenverkehrsordnung) section on speed begins with the requirement which may be rendered in English:

Any person driving a vehicle may only drive so fast that the car is under control. Speeds must be adapted to the road, traffic, visibility and weather conditions as well as the personal skills and characteristics of the vehicle and load.

Traffic signs, installations, and symbols used in Germany are prescribed by the Road Traffic Regulation (StVO) and the Traffic Signs Catalog (VzKat).

Road signs in New Zealand are similar to those set by the Vienna Convention on Road Signs and Signals. While New Zealand is not a signatory to the convention, its road signs are generally close in shape and function. New Zealand uses yellow diamond-shaped signs for warnings in common with Australia, the Americas, Ireland, Japan and Thailand. Speed limit signs are a red circle with a white background and the limitation in black, and are in kilometres per hour. There are also some signs unique to New Zealand. Road signs in New Zealand are controlled by the NZ Transport Agency and are prescribed in the Land Transport Rule: Traffic Control Devices 2004 and set out in the Traffic Control Devices (TCD) Manual.

Road signs in Indonesia Overview of road signs in Indonesia

Road signs in Indonesia are standarized road signs similar to those used in other nations but with certain distinctions. As a former Dutch colony, until the 1970s road signs in Indonesia closely followed The Netherlands rules on road signs. Nowadays, Indonesian road sign design are a mix of European, US MUTCD, New Zealand, and Japanese road sign features. According to the 2014 Minister of Transport's Regulation No. 13 concerning Traffic Signs, the official typeface for road signs in Indonesia is Clearview. Indonesia formerly used FHWA Series fonts as the designated typeface though the rules are not being implemented properly.

Road signs in Australia Overview of road signs in Australia

Road signs in Australia are regulated by each state's government, but are standardised overall throughout the country. In 1999, the National Transport Commission, or NTC, created the first set of Rules of the Road for Australia. Official road signs by standard must use the AS1744 series fonts, based on the USA's Highway Gothic typeface.

Road signs in Azerbaijan are similar to the Russian road sign system that ensure that transport vehicles move safely and orderly, as well as to inform the participants of traffic built-in graphic icons. These icons are governed by the Vienna Convention on Road Traffic and Vienna Convention on Road Signs and Signals.


  1. "AS1742.2-2009 Manual of Uniform Traffic Control Devices, Part 2" (PDF).
  2. "Mainroads Western Australia Static Rollover Threshold Calculator".
  3. 1 2 "Autobahnrichtgeschwindigkeitsverordnung" (PDF) (in German). German Federal Government. Archived from the original (PDF) on 29 September 2007. Retrieved 2007-10-28.
  4. "The difference between speed limits and suggested speeds".
  5. "Heavy Vehicle Stability Guide, P.11" (PDF). NZ Transport Agency.
  6. "Curve speed management July 2007 (Research Report 323, section 4)" (PDF). Land Transport New Zealand.
  7. "Safer motorway driving". Department for Transport. Archived from the original on 2007-06-09. Retrieved 2007-10-28.
  8. "Speed limits". Bristol City Council. Archived from the original on 2007-10-17. Retrieved 2007-10-28.
  9. Pesti, Geza; Jessen, Daniel; Byrd, Patrick; McCoy, Patrick. "Traffic Flow Charactaristics of the Late Merge Work Zone Control Strategy" (PDF). Transportation Research Board. Archived from the original (PDF) on 2016-05-30.Cite journal requires |journal= (help)
  10. "Speeding buses put lives at risk". Manchester Evening News . 2005-04-26. Retrieved 2007-10-28.
  11. Manual on Uniform Traffic Control Devices (2009 edition), Section 2C.06