The 1968 Vienna Convention on Road Signs and Signals allows for two types of stop sign, as well as three acceptable variants. Sign B2a is a red octagon with the inscription "STOP" in white. Sign B2b is a red circle with a red inverted triangle with either a white or yellow background, and the inscription "STOP" in either black or dark blue. The Convention allows for the word "STOP" to be in either English or the national language of the particular country. The finalized version by the United Nations Economic and Social Council's Conference on Road Traffic in 1968 (and in force in 1978) proposed the standard stop sign diameters of 600, 900 or 1200 mm.
In the United States, stop signs have a size of 750 mm across opposite flats of the red octagon, with a 20 mm white border. The white uppercase letters in small caps forming the stop legend are 250 mm tall. Larger signs of 900 mm (35 in) with 300 mm (12 in) legend and 25 mm (⅞ in) border are used on multi-lane expressways. Regulatory provisions exist for extra-large 1,200 mm (47 in) signs with 400 mm (16 in) legend and 30 mm (1 1⁄4 in) border for use where sign visibility or reaction distance are limited, and the smallest permissible stop sign size for general usage is 600 mm (24 in) with a 200 mm (7.9 in) legend and 15 mm (⅝ in) border. The metric units specified in the US regulatory manuals are rounded approximations of US customary units, not exact conversions. The field, legend, and border are all retroreflective. In the Vienna Convention on Road Signs and Signals of the UN, the instruction on the sign to stop is specified to be either in English as stop or written in the local language. Some countries use both. The sign's distinctive design was developed and first used in the US, and later adopted by other countries and by the UN. Despite this, the US is not a signatory to this UN Convention; the US has the same sign design as specified by the Convention, which adopted the US standard.
Stop signs are used globally. However, most countries see fewer of them than North America and South Africa, because all-way stops are never used and may even be legally prohibited. In a majority of European and Central Asian countries, as well as Cuba in North America, junctions without traffic lights or roundabouts are controlled by stop signs on minor roads and by white, yellow and black priority diamond signs on the major road. In the UK, the Netherlands, Scandinavia, New Zealand and Australia, stop signs are restricted to situations wherein coming to a dead stop is actually necessary because of severely limited sight lines. At the vast majority of minor intersections in these countries Give Way signs and/or equivalent road markings are used. Finally, at the busier crossing streets, Give Way signs may be replaced by (mini) roundabouts, which also work on the give way (rather than stop) principle.
Stop signs are often used in North America to control conflicting traffic movements at intersections that are not busy enough to justify the installation of a traffic signal or roundabout. In the United States, the stop sign is not intended for use as a traffic calming device; it is intended to be installed mainly for safety and/or to assign right-of-way for a certain direction. Nevertheless, in the United States, Mexico and Canada, stop signs are commonly deployed as supposed safety measures in residential areas and near places where children play or walk (such as schoolyards), or that experience frequent automobile collisions, making extra precautions necessary. Stop signs may be erected on all intersecting roads, resulting in three- and four-way stops. However, studies have confirmed that stop signs do not offer measurable safety benefits over the Yield approach adopted in the countries listed above based on original European research dating back many decades.
More recently, Georgia Traffic Engineer Martin Bretherton Jr. reviewed over 70 technical papers to find that multi-way stop signs do not typically control traffic speeds, and can create a variety of problems, including liability issues, traffic noise, pollution, enforcement problems and poor stop compliance when drivers feel that the signs have no justification. Fifteen studies found that unwarranted multi-way stops actually increased speed away from intersections as motorists try to make up lost time spent at "unnecessary" stop signs. Multi-way stop signs impose high vehicle operating costs, longer than needed travel times, excessive fuel consumption and increased vehicle emissions.
Researchers also found that safety of pedestrians (especially small children) may sometimes be actually decreased. Pedestrians expect vehicles to stop, but many drivers run the "unnecessary" signs. Engine exhaust, brake, tire and aerodynamic noise may all increase as cars brake and then accelerate up to speed. While the initial cost of installing stop signs is low, enforcement costs can be prohibitive, and one 1990 study estimated extra travel costs per intersection as $210,061/year. Finally, where unwarranted multi-way stops have been successfully removed with public support, results have included improved compliance at justified stop signs.
Another major issue surrounding the use of stop signs pertains to the public's variegated understanding of their meaning. One prolific source of crashes is the misconception of law that every motorist who attempts to enter a main highway from a side road, does so at his or her peril. Such motorists usually have very definite rights granted by provisions of state vehicle codes, which provide that after the driver has 'yielded' by stopping at an arterial sign he or she may proceed and the drivers of all other vehicles approaching the intersection on the through highway shall yield the right of way to the vehicle crossing the through highway. Where a car has actually entered an intersection before the other approaches it, the driver of the first car has the right to assume that he or she will be given the right of way and be permitted to pass through the intersection without danger of collision. He or she has a right to assume that the driver of the other car will obey the law, slow down, and yield the right of way, if slowing down be necessary to prevent a collision. In order to be able fulfill the duty of yielding to entering motorists who have established control of the intersection, the through-driver must travel no faster than permitted by the assured clear distance ahead.
Vehicles that are approaching an intersection from beyond the subtended angular velocity detection threshold (SAVT) limit may be perceived with subjective constancy by the stopped driver; which means the oncoming vehicle cannot be reliably distinguished between moving or parked or give insight to time-to-collision, though they may be traveling at such an imprudent speed as to pose an immediate hazard. An entering driver must have fair notice that his or her contemplated conduct is forbidden by such hazard for it to be illegal.
Stop sign placement can pose an additional challenge to users. There is a trade-off between the salient visual cues provided by increased limit line set-back, and the crucial time that is lost in approaching the intersection from behind that line; being closer can provide a few additional seconds requisite for safe transit. However, common creeping into the intersection past the limit line causes drivers to lose the invaluable perspective of the visual acuity of lateral motion, crippling them to the more dangerous SAVT. This makes it very difficult to estimate the movement of oncoming traffic. As intersections are not engineered to be used this way, the traffic flow ideals have broken down when drivers consistently choose this method as the safer alternative. Stop signs are accompanied with a limit line, which has a mandatory set-back distance which is often not less than 15 feet. While it may be negligence per se to prematurely pass the stop limit line, drivers may be unfairly denied sufficient time gap or opportunity to enter otherwise because of the through-traffic flow and speed; the inherent problem with this traffic control device. While stop signs are a relatively inexpensive method of traffic management, they can be expensive from perspective of the damage they cause users. Pricey but safer traffic signals, roundabouts, and traffic circles are alternatively used where traffic flow dictates it is inappropriate to use a stop sign. It is just as crucial for law enforcement to regulate traffic through-speed that is above the assured clear distance ahead ahead as it is to cite stop sign runners for this device to be a viable option.
A pivoting arm equipped with a stop sign is a piece of equipment required by law on North American school buses. The sign normally stows flat on the left side of the bus, and is deployed by the driver while picking up or dropping off passengers. Some buses have two such stop arms, one near the front facing forwards, and one near the rear facing backwards. The stop sign is retroreflective and equipped either with red blinking lights above and below the stop legend, or with a stop legend that is illuminated by LEDs. Unlike a normal stop sign, this sign requires other vehicles travelling in both directions to remain stopped until the sign is retracted.
In the UK, stop signs may be placed only at sites with severely restricted visibility, and each must be individually approved by the Secretary of State for Transport. Section 79 of the Highways Act 1980 enables the government to improve visibility at junctions, as by removing or shortening walls or hedges, in preference to placing a stop sign. The former UK practice of using "Halt" or "Slow" at Major Road Ahead signs was discontinued in 1965 at the recommendation of the Worboys Committee. Instead of replacing all the old "Halt" signs with the new Vienna Convention "Stop" sign, "Give Way" became the standard sign at UK priority junctions.
Laws and regulations regarding how drivers must comply with a stop sign vary by jurisdiction. In the United States and Canada, these rules are set and enforced at the state or provincial level. At a junction where two or more traffic directions are controlled by stop signs, generally the driver who arrives and stops first continues first. If two or three drivers in different directions stop simultaneously at a junction controlled by stop signs, generally the drivers on the left must yield the right-of-way to the driver on the far right.
In all countries, the driver must come to a complete stop before entering a stop-controlled intersection, even if no other vehicle or pedestrian is visible. If a stop line is marked on the pavement, they must stop before crossing the line.
However, some drivers slow but don't come to a complete stop. This maneuver is called a rolling stop or nicknamed after a city or region regarded as somewhere it is commonplace (e.g., "Rhode Island roll" or "California stop") – slowing down significantly but not stopping completely at the sign. This partial stop is not acceptable to most law enforcement officials, and can result in a traffic citation.
In some jurisdictions, most notably Idaho, the traffic code allows for cyclists approaching a stop sign to slow to a "reasonable speed" and yield to conflicting traffic, but does not mandate a full stop unless "required for safety". This is commonly known as an "Idaho stop" or "stop-as-yield". The Idaho law has been in effect since 1982 and has not been shown to be detrimental to safety. Cyclist advocacy groups have sought similar laws for other jurisdictions in the United States.
Stop signs originated in Michigan in 1915. The first ones had black lettering on a white background and were 24 by 24 inches (61 cm × 61 cm), somewhat smaller than the current sign. As stop signs became more widespread, a committee supported by the American Association of State Highway Officials (AASHO) met in 1922 to standardize them, and selected the octagonal shape that has been used in the United States ever since. The unique eight-sided shape of the sign allows drivers facing the back of the sign to identify that oncoming drivers have a stop sign and prevent confusion with other traffic signs. It was also chosen so that it could be identified easily at night, since the original signs were not reflective. The National Conference on Street and Highway Safety (NCSHS), a group competing with AASHTO, advocated a smaller pink-on-yellow stop sign. These two organizations eventually merged to form the Joint Committee on Uniform Traffic Control Devices, which in 1935 published the first Manual on Uniform Traffic Control Devices for Streets and Highways (MUTCD) detailing the stop sign's specifications.
The MUTCD stop sign specifications were altered eight times between 1935 and 1971, mostly dealing with its reflectorization and its mounting height. From 1924 to 1954, stop signs were made with a black stop legend on a yellow field. The reflective sign, initially yellow, was developed by the reflective applications division of 3M spearheaded by Joseph E. Van Kirk, Sr.. The sign gained its current white legend/red field color configuration. Red signifies stop on traffic signals, so this specification unified red as a stop signal whether indicated by sign or by light. The original decision to use a yellow background for the stop sign was based “largely on the unavailability of red pigments that would not fade on exposure.” The mounting height reached its current level of 7 ft (2.13 m) in 1971; previously, stop signs were typically mounted 2–3 feet (0.61–0.91 m) above the ground.
The already-widespread use of the MUTCD stop sign became law in the United States in 1966. In 1968, this sign was adopted by the Vienna Convention on Road Signs and Signals as part of United Nations Economic Commission for Europe's effort to standardize road travel across borders. The Convention specifies that 'stop' be written in English or the national language and allows an alternative circular yellow sign. Many European countries are party to the Convention. English-speaking countries, the exception being India, are not party to the Convention but usually use the red octagonal stop sign per their own standards, like the MUTCD. Even in countries not associated with either standard mentioned above, the red octagonal stop sign is often used. Unique types of stop signs may still be observed in countries like Japan.
Although all English-speaking and many other countries use the word stop on stop signs, some jurisdictions use an equivalent word in their primary language instead of or in addition to it. Israel uses the image of a hand in a "stop" gesture.
In some Caribbean and South American countries (Argentina, Bolivia, Brazil, Chile, Colombia, Cuba, Dominican Republic, Ecuador, Paraguay, Peru, Puerto Rico, Uruguay and Venezuela), signs bear the legend pare ("stop" in Portuguese and Spanish). Mexico and Central American countries bear the legend alto ("halt") instead.
In the Canadian province of Quebec, modern signs read either arrêt or stop; however, it is not uncommon to see older signs containing both words in smaller lettering, with arrêt on top. Both stop and arrêt are considered valid French words and the Office québécois de la langue française (OQLF) notes that the use of "stop" on stop signs is attested in French since 1927. At the time of the debates surrounding the adoption of the Charter of the French Language ("Bill 101") in 1977, the usage of "stop" on the older dual-word signs was considered to be English and therefore controversial; some signs were occasionally vandalized with red spray paint to turn the word stop into "101". However, it was later officially determined by the OQLF that "stop" is a valid French word in this context, and the older dual arrêt + stop usage is therefore not considered bilingual but merely redundant and therefore deprecated (à éviter). All newly installed signs thus use either one word or the other, but not both. In practice, the vast majority of signs use "arrêt" in the province of Québec. The "stop" word is usually seen in predominantly english-speaking areas.
The province of New Brunswick has bilingual stop arrêt in English-speaking areas. Acadian regions of Nova Scotia and Prince Edward Island also have bilingual signs. Some areas in Manitoba and Ottawa, Ontario also have bilingual signs, as do entrances to the country through Canada Customs. On First Nations or Inuit territories, stop signs sometimes use the local aboriginal language in addition to or instead of English, French or both. Other parts of Canada use stop. The use of native languages is also commonplace on U.S. native reservations, especially those promoting language revitalization efforts.
The white text on red background appearance is usually the same. Exceptions include Japan, which uses an inverted solid red triangle, and Zimbabwe, which (until 2016) used a disc bearing a black cross.
The red octagon with "STOP" in the English language has become the most common version of the stop sign used around the world. Many countries however use different variations.
A number of laboratory researchers have reported values of the looming threshold to be in the range of 0.003 radian/sec. Forensic practitioners routinely use elevated values of the looming threshold, e.g., 0.005-0.008, to account for the complexity of real-world driving tasks. However, only one source has used data from actual vehicle accidents to arrive at a looming threshold – and that value, 0.0275 rad/sec, is an order of magnitude larger than that derived from laboratory studies. In this study, we examine a much broader range of real-world accident data to obtain an estimate of the reasonable upper end of the looming threshold. The results show a range of 0.0397 to 0.0117 rad/sec...
Displacement thresholds for peripheral motion were affected by acuity limits for speeds below 0.5 degrees/s.
The driver of any vehicle approaching a stop sign at the entrance to, or within, an intersection shall stop at a limit line
The MUTCD approved by the Federal Highway Administrator is the national standard for all traffic control devices installed on any street, highway, or bicycle trail open to public travel in accordance with 23 U.S.C. 109(d) and 402(a)...Where State or other Federal agency MUTCDs or supplements are required, they shall be in substantial conformance with the National MUTCD.
Chapter 3B.16.10: If used, stop and yield lines should be placed a minimum of 4 feet in advance of the nearest crosswalk line at controlled intersections...In the absence of a marked crosswalk, the stop line or yield line should be placed at the desired stopping or yielding point, but should not be placed more than 30 feet or less than 4 feet from the nearest edge of the intersecting traveled way.
Chapter 405.1: Set back for the driver of the vehicle on the crossroad shall be a minimum of 10 feet plus the shoulder width of the major road but not less than 15 feet.