|
For a discussion of the maximum speed possible in the universe, see speed of light and special relativity. A road speed limit is the maximum speed allowed by law for road vehicles. Ignoring countries without a speed limit, the highest speed limit is 160 km/h (100 mph), experimentally posted on selected test stretches in Austria and the United Arab Emirates. Very few public roads have no speed limit. The first speed limit was the 10 mph limit introduced by the Locomotive Act of 1861 in the United Kingdom. Some roads also have minimum speed limits, where slow speeds are considered to impede traffic or be dangerous. Factors in Setting Speed Limits Speed limits are set based on many factors, such as road features, crash records, legal statutes, administrative judgment, engineering judgment and political dictate. Two common measures for setting speed limits are the design speed of the road and the 85th percentile of travel speeds (See Design Speed, Operating Speed, and Posted Speed Practices). Definition In the United States, the design speed is officially defined as "a selected speed used to determine the various geometric design features of the roadway", according to the 2001 American Association of State Highway and Transportation Officials highway design manual, commonly referred to as the "Green Book". Previous versions of the Green Book referred to design speed as the "maximum safe speed that can be maintained over a specific section of highway when conditions are so favorable that the design features of the highway govern"; however the 2001 edition removed the term "safe" in order to avoid the implication that speeds greater than the design speed were necessarily "unsafe". Limitations Safe operating speeds can exceed the design speed. Example reasons include: In commonly accepted engineering practice, design speed is considered a "first guess" at an appropriate speed limit. 85th percentile rule In the United States, traffic engineers may rely on the 85th percentile rule to establish speed limits. The speed limit should be set to the speed that separates the bottom 85% of vehicle speeds from the top 15%. The 85th percentile is slightly greater than a speed that is one standard deviation above the mean of a normal distribution. The theory is that traffic laws that reflect the behavior of the majority of motorists may have better compliance than laws that arbitrarily criminalize the majority of motorists and encourage violations. The latter kinds of laws lack public support and often fail to bring about desirable changes in driving behavior. An example is the federally-mandated 55 mph (90 km/h) speed limit that was scrapped in part because of notoriously low compliance. Traffic engineers observe that the majority of drivers drive in a safe and reasonable manner, as demonstrated by consistently favorable driving records. Studies have shown crash rates are lowest at around the 85th percentile. Vehicles traveling over the 85th percentile speed (or faster than the flow of traffic) have a significantly higher crash risk than vehicles traveling around or modestly below this speed. Most U.S. jurisdictions report using the 85th percentile speed as the basis for their speed limits, so the 85th-percentile speed and speed limits should be closely matched. However, a review of available speed studies demonstrates that the posted speed limit is almost always set well below the 85th-percentile speed by as much as 8 to 12 mph (see p.88) (13 to 19 km/h). Some reasons for this include: Signage
Speed limits in specific countries The following table shows the respective speed limits (excepting the local 30 km/h or lower limits in many countries) in km/h (mph for the United Kingdom and the United States in brackets): Remarks: 1 130 km/h is the recommended maximum speed on motorways, as indicated by a blue sign. Many sections of the German motorway network are now covered by speed limits, usually ranging from 80 to 130 km/h (140 km/h as speed limit is being tested in Lower Saxony -some politicians are against it, because 140 km/h is over the recommended maximum speed, depending on local conditions (i.e., frequent traffic, terrain, etc.). It is usual for drivers involved in crashes who were exceeding the 'recommended' speed limit to be held to be at least partly at fault, regardless of the circumstances of the crash, and insurance companies have the right to withhold payment. 2 110 km/h for motorcycles. 3 Two-lane expressways: 130 km/h; three-lane expressway: 150 km/h (since 2003, the speed limit of 150 km/h is only valid when signed). 4 Cars with heavy trailer: 80 km/h; lorries with heavy trailer: 70 km/h. 5 Cars with heavy trailer: 100 km/h; lorries with heavy trailer: 80 km/h. 6 During winter, when conditions are often bad, all Finnish motorways have a speed limit of 100 km/h or less. 7 Additional trailer checkup (TÜV) and special speed plaque required on vehicle. 8 Effective January 20, 2005 9 A provisional increase of the speed limit on motorways from 90 to 100 km/h was made permanent when the number of accidents decreased. 10 Signs are posted in mph, a situation unlikely to change in the near future. 11 100 km/h is default limit on all National Routes regardless of design standard when local limits do not apply. 12 Iceland does not have expressways/motorways in the traditional sense. There is really only one such road, with three and four lanes and no traffic lights. It is within city limits, and the maximum speed is 80 km/h. 13 Between 90 and 110 km/h depending on how many lanes the road has. 14A provisional increase on a 12 km stretch. 15 Built up area speed limit of 50 km/h in all states and territories except for the Northern Territory, where it remains at 60 km/h. The Northern Territory also has no default limit outside built up areas, but, starting in January 2007, a speed limit of 110 or 130 km/h will be imposed on roads in rural areas. Western Australia has a rural limit of 110 km/h. See separate article for details. 16 Speed limit is 110 km/h in several provinces, 100 km/h in others. Europe In some countries in Europe, "traffic calming" is gradually becoming a regular part of urban traffic management, after a long evolution of opinions and attitudes towards car use and vulnerable road users. Regulations for "30 km/h zones" have been enacted from about 1980 and have been widely applied. New urban policies have been defined with a view to encouraging a switch from car use to public transport and non-motorised modes (cycling, walking), with the additional condition of lower speeds to improve safety of vulnerable road users, for example national policies such as "sustainable safety" in the Netherlands or "vision zero" in Sweden. United Kingdom
France On French autoroutes there is a variable speed limit: in dry weather, 130 km/h (80 mph); when raining, 110 km/h (68 mph). In 2005, a governmental report advised lowering the higher speed to 115 km/h (71 mph) in order to save fuel and reduce accident risks, but this proposal was badly received. Since 2002, the French government has installed a number of automatic radar guns on autoroutes, routes nationales, and other major thoroughfares. These are in addition to radar manned by the French National Police or Gendarmerie. The French authorities have credited this increase in traffic enforcement with a 21% drop in road fatalities from 2002 to 2003. Germany German autobahns are famous for having no universal speed limit, although about 30 % of them have posted speed limits and about 10 % are equipped with motorway control systems that can show variable speed limits.• No national speed limit also applies to rural roads with a central reservation or a minimum of two marked lanes per direction. Instead, there is an advisory speed limit (Richtgeschwindigkeit) of 130 km/h (80 mph). While driving at higher speeds is no offence, the increased risk induced by higher speeds (erhöhte Betriebsgefahr) may result in partial liability for damages. On all of these roads, speed limits do apply to lorries, buses, and cars towing trailers. While speeds over 200 km/h (124 mph) are not uncommon, most drivers choose much lower speed around 130 to 150 km/h (80 to 93 mph). Further, the speed is also limited by traffic density and the type of the car - those with smaller engines often cannot exceed 160 to 180 km/h (100 to 112 mph) and most manufacturers of powerful cars deliberately limit the maximum speed of their products to 250 km/h (155 mph). At daytime, it is often impossible to drive at high speeds for more than a few kilometres. Rising oil prices also have a chilling effect on the strive for high speeds. The introduction of a national speed limit for motorways and similar roads has been on the agenda of various political and environmentalist groups for decades. However, there are no definite plans for this at present. On rural roads that are neither motorways nor similar roads, there is a national speed limit of 100 km/h (60 mph). Lower speed limits apply to lorries, some buses, and cars towing trailers. In built-up areas, there's a speed limit of 50 km/h (30 mph) but residential areas usually have a posted speed limit of 30 km/h (20 mph). On arterial roads, the speed limit may be rised to 60 or 70 km/h (37 to 43 mph). Italy Italian Autostradas have a 130 km/h speed limit (80 mph), with 110 km/h (70 mph) limits on curvy roads and in rainy conditions and 150 km/h (95 mph) limits on newer and straighter roads. Switzerland Swiss Autobahnen, Autoroutes and Autostrada are limited to 120 km/h (75 mph). Semi-motorways, known as "motor roads", Autostrassen or semi-autoroutes generally have a limit of 100 km/h (60 mph). Sweden From about 1990 to 1995, Sweden lowered the limit in the large city provinces from 110 km/h (70 mph) to 90 km/h (55 mph), the lowest in Europe at the time, citing environmental reasons. The term "large city province" was defined as a province including one of the three large cities with suburbs. That meant that the west coast motorway E6 had a 90 km/h (55 mph) limit on its (then) about 250 km of motorway, but some ordinary roads in less densely populated provinces had a 110 km/h (70 mph) limit. This reduced limit was later removed because it was neither popular nor well obeyed. Netherlands Since May 2002 the Netherlands has been experimenting with 80 km/h (50 mph) zones on motorways crossing suburban areas. The first zone to be implemented was on the A13, connecting Rotterdam to the Hague, at the Rotterdam suburb of Overschie. This was generally accepted as a success, so in 2005 the experiment was expanded, with four new zones in Rotterdam, the Hague, Utrecht and Amsterdam. DCMR report (Dutch). The new zones have had mixed results, causing great controversy and calls for the removal of them. North America
United States American speed limit signs usually read "SPEED LIMIT XX", such as "SPEED LIMIT 50" for 50 mph (80 km/h). A minimum speed sign reads "MINIMUM SPEED XX", such as "MINIMUM SPEED 45" for 45 mph (70 km/h). Speed limits on United States roads are usually: Canada Since 1977, Canadian speed limits have been in km/h - they were previously in mph. A sign reads "MAXIMUM XX", such as "MAXIMUM 80" for 80 km/h. A minimum speed sign reads "XX MINIMUM", such as "60 MINIMUM" for 60 km/h. Typical speed limits are: Note that where more than one limit is given per road, it usually indicates a difference between provinces; however, within provinces, different roads of the same classification have different speed limits. For example, in Alberta and Nova Scotia some freeways have a limit of 100 km/h, while others have a speed limit of 110 km/h (70 mph). In Ontario, all freeways have a maximum speed limit of 100 km/h unless there is a lower posted limit. Speed limits are generally lower in Ontario and Quebec on comparable roads than in other Canadian provinces, except perhaps British Columbia. Examples of this disparity include rural two-lane highways in Ontario which have a standard speed limit of 80 km/h, while comparable roads in other provinces have standard speed limits of 90–100 km/h. In rural western Ontario, however, some two-lane roads have speed limits of 90 km/h. In British Columbia, a review of speed limits conducted in 2002 and 2003 for the Ministry of Transportation found that posted limits on investigated roads were unrealistically low for 1309 km and unrealistically high for 208 km. The reports recommended to increase speed limits for multi-lane limited-access highways constructed to high design standards from 110 km/h to 120 km/h. As described in that report, the Ministry is currently using "...Technical Circular T-10/00 ... to assess speed limits. The practice considers the 85th percentile speed, road geometry, roadside development, and crash history." In Canada, as in most other locales, speed violation fines are double (or more) in construction zones. China Previously, all expressways in the People's Republic of China were limited to 110 km/h. With the passage of the PRC's first road-related law, the Road Traffic Safety Law of the People's Republic of China, the speed limit was raised to 120 km/h from May 1, 2004; however, the updating of signs will still take some time. Semi-expressways and city express routes (called kuàisù gōnglù () in Chinese, meaning "high speed public road") generally have lower speed limits of 100 km/h: in some cases the speed limit may be lower. On China National Highways (which are not expressways), a common speed limit is 80 km/h. In localities, speed limits may drop to 40 km/h. In reality, few people drive according to the speed limits, and on most roads, enforcement cameras are non-existent. Where an enforcement camera does exist, it is marked "speeding detection camera" (). On some designated "fast through routes" in cities, speed limits are up to 80 km/h. Otherwise, speed limits are 70 km/h on roads with two uninterrupted yellow lines and 60 km/h or 50 km/h otherwise. Signage in towns and on expressways is often present. Minimum speed limits on expressways vary. A general minimum speed limit of 60 km/h is in force at all times (although traffic jams more than thwart it). The maximum speed limit, as posted on Chinese motorways is 120 km/h. This is a recent change. India India has a speed limit in towns and this is usually signed. It is a contracting party to the "United Nations Conventions on Road Traffic, Road Signs and Signals". Road condition is historically poor, discouraging high speeds, but in Maharashtra in particular, the roads have been substantially improved in recent years due a buoyant economy. India for the past few years has embarked on a large road building effort with some 47,000 kilometres of world class motorway reportedly under construction, and finalised. (National Highways Agency India). On highways where speed restrictions end, it is signaled by use of the 'speed derestriction' sign (), known by catalogue number in the UN Convention as a C,17a 'End of all local prohibitions imposed on moving vehicles'. Most smaller roads in or near cities have speed limits set at 30 km/h. Most stretches of highway are limited to 60 km/h, such as National Highway 4. Japan The general limit is 60 km/h except for divided national highways where the limit is 100 km/h. Urban areas are usually zoned at 40 km/h. Limits in Japan are different from most countries by: Malaysia See also: National Speed Limits The speed limit in Malaysia is 110 km/h on closed toll expressways. Speed limit on federal, state and municipal roads is between 50 km/h and 90 km/h depending on geographical factors along the road. The default speed limit is 90 km/h and it is reduced to 60 km/h in urban areas. The highway police monitor the speed of passing cars from beneath a bridge or signboard. Several years ago, a proposal to increase the speed limit on Malaysian expressways to 120 km/h was made but was finally rejected in 2005 by Minister of Works, Datuk Seri S. Samy Vellu, stating that most drivers often drive 10 km/h faster than the stated speed limit on the expressways, and therefore they will drive at 130 km/h if the 120 km/h speed limit is imposed. Singapore The speed limit of Singapore highways/expressways is 80km/h. However, Eastcoast Parkway(ECP) has its speed limit raised to 90km/h in recent years. Speed limit of other highways/expressways remains. Taiwan The Act Governing the Punishment of Violation of Road traffic Regulations () is the basic law. The Road Traffic Security Rules () are the basic administrative regulations. When no other limits are posted, the default speed limits are: Speed limits on freeways are posted by signs, generally 100 km/h. Limited segments are posted at 90, 80, or 70 km/h. Most segments of the National Highway No. 3 are now posted at 110 km/h, the highest speed limit in Taiwan. A truck with a gross weight of 20 tonnes or more is limited to 90 km/h. Except on approaches to toll stations and work areas, minimum speeds are usually posted at 60 km/h. Australia Australian states and territories use a combination of default speed limits and speed zones. The default limits apply in the absence of a speed zone and are: New Zealand Speed limits in New Zealand range from 20 km/h to 100 km/h. Specifically: Signage tends to follow the European model of a number inside a red circle. Sometimes "open road limit" occurs as a black bend sinister inside a thin black ring. The letters LSZ (Limited Speed Zone) indicate that the limit is 100 km/h unless conditions (visibility, road condition, rain, many other road users) would make this unwise, in which case it is 50 km/h. This type of speed limit can longer be set since 2003 and are progressively being replaced. A local bylaw in Auckland produced the curious speed limit of 16 km/h in Waikumete Cemetery. When New Zealand converted from Imperial to metric measure the statues concerning speed in this location were not updated even though the signage legally had to be altered from Imperial units. This limit existed into the early 21st century. Typically speeds in such areas were 10, 15, or 20 km/h after adoption of the metric system. There is no minimum speed limit but vehicles travelling less than the maximum and which are followed by other vehicles must keep to the side of the road and pull over to allow others to pass as soon as is safe. Some vehicles are restricted to lower speeds: There are also has variable speed limits in some areas, such as school zones. Namibia The general speed limits in Namibia are (according to Road Authority of Namibia): South Africa The general speed limits in terms of the South African National Road Traffic Act, 1989 and its Regulations are: Enforcement
Enforcement tolerance Speed limit enforcement often begins at a small amount above the speed limit. For example, speeding citations for 1 unit (mph or km/h) above the limit are exceedingly rare. In certain cases, such as Houston, Texas, only 1% of speeding citations are for less than 10 mph (16 km/h) above the speed limit (Houston Chronicle, "It's really true: Drivers going less than 10 mph over limit rarely ticketed", November 24, 2002). In the United States, speeding enforcement tolerance is usually up to the discretion of the arresting officer. A small tolerance is almost always allowed even where traffic signs advise "NO TOLERANCE." Some states have official tolerances, such as Pennsylvania. As per state law, you cannot be cited for traveling less than 10 mph over a speed limit of less than 55 mph or for traveling less than 6 mph over a speed limit of 55 mph or greater. In Taiwan, even though the Regulations on Establishing Traffic Signs and Indicating Lines () define the speed limit signs to show absolute limits, the police agencies have generally agreed a tolerance of up to 10 km/h. A notable exception was the Hsuehshan Tunnel opened on June 16, 2006 with automated speeding cameras. After the zero tolerance on speeding created controversy, effective 00:00 (UTC+8) on September 16, 2006, a tolerance of 10 km/h has been allowed in the same way as other Taiwanese roads. * Essential physics The kinetic energy involved in a motor vehicle collision is proportional to the square of the speed at impact. The probability of a fatality is, for typical collision speeds, empirically correlated to the fourth power of the speed difference at impact, rising much faster than kinetic energy. To illustrate these statistics, suppose two vehicles crash into a massive, fixed object, and one vehicle’s speed is 10% greater than the other vehicle. The faster vehicle will release 21% more energy, and its occupants will experience a 46% higher probability of a fatality. It should be noted that crashes with dramatic, sudden speed changes that terminate almost all velocity are atypical. These kinds of crashes include head on collisions or collisions with massive, fixed objects like trees or concrete bridge piers. Although the basic relationship between vehicle speed and crash severity is unequivocal and based on the laws of physics, the probability of a crash as well as crash severity can be mitigated. Safety devices like crash attenuators, barriers, or wide medians are examples. The highest degree of mitigation is found on motorways (which may be called freeways, limited access highways, also Autobahns, Interstates or other national names), which are internationally documented as being the safest roads per mile travelled despite their higher speeds, due to designing out of most conflict opportunities as well as restricted access. Speed limits, actual speeds, and aggregate safety The 1998 Synthesis of Safety Research Related to Speed and Speed Management sponsored by the US Federal Highway administration found, "on freeways and other high-speed roads, speed limit increases generally lead to higher speeds and crashes." Increasing a speed limit by 4 mph (6 km/h) would increase the average speed by 1 mph (1.6 km/h) and increase injury accidents by 5%. The report cautions that "changing speed limits on low and moderate speed roads appears to have little or no effect on speed and thus little or no effect on crashes". The report noted that traffic calming significantly reduced speeds and injuries in treated areas but that the decrease may be due to reduced traffic volumes. The report also suggests that "variable speed limits that adjust with traffic and environmental conditions could provide potential benefits" as most of the speed related crashes involve speed too fast for conditions. The report noted the landmark study (D. Solomon, "Accidents on Main Rural Highways Related to Speed, Driver, and Vehicle", Federal Highway Administration, Washington, DC, July 1964) that observed a "U-shaped curve" of crash probability versus speed, where crash rates were lowest for travel speeds near the mean speed of traffic, and increased with greater deviations above and below the mean. Subsequent research has found that "The occurrence of a large number of crashes involving turning maneuver partly explains the increased risk for motorists traveling slower than average and confirms the importance of safety programs involving turn lanes, access control, grade separation, and other measures to reduce conflicts resulting from large differences in travel speeds." Speed and crash factors Some safety factors are not always under the full control of the driver, such as driver alertness and distractions, road conditions, weather, daylight availability, actions and alertness of other drivers, and wildlife. While these factors are not directly related to vehicle speed, the effects of these factors can be more severe with more speed. For example, a deer running across the road has no consequences to a parked vehicle but could have disastrous consequences for a vehicle traveling at 100 mph (160 km/h). This suggests that lower speeds can reduce the frequency and severity of crashes; lower speeds can give the driver more time to respond appropriately in the face of unexpected dangers, and it can reduce the severity of a crash should one happen. However, since the efficacy of speed limits in restraining driver speed is subject to debate, it is not clear how well speed limits can ameliorate these other factors. Another view is that, while speed can play a part of the causal chain which leads to crashes, speed's role is mostly to magnify the consequences of other unsafe acts. This viewpoint is reinforced by the fact that speed is rarely the sole crash factor. In many cases, removing the other crash factors, such as a right of way violation, would have absolutely prevented the collision. While reducing the speed could have a beneficial effect on the severity and probability of the crash, it usually cannot guarantee crash prevention. Most 'speed-related' crashes involve speed too fast for conditions such as limited visibility or reduced road traction, rather than in excess of the posted speed limit. Most speed-related crashes occur on local and collector roads with relatively low speed limits. However, most speed-related traffic citations involve speeds in excess of posted maximum speed limits. Variable speed limits (q.v.) offer some potential to reduce speed-related crashes, but due to the high cost of implementation exist primarily on motorways. Speed-related crashes can occur on high speed limit roads at low speeds, e.g. below 30 mph; for example, truck rollovers on exit ramps. Variable speed limits
Opposition Speed limits and their enforcement have been opposed by some motorists since their inception. Britain's first motoring organization, the AA, was formed to warn members about speed traps. Other organizations, such as the Association of British Drivers, Safe Speed, the North American National Motorists Association, and German Auto Club ("ADAC"), have sought to ban or discredit certain speed limits as well as other measures, such as automated camera enforcement. The debate over speed limit enforcement has become a large part of the road safety and environmental policy debate in some countries. Critics of speed limits and strict enforcement outside built-up areas point to: Prior to the (now defunct) 1974 national 55 mph (88 km/h) speed limit in the U.S., German Autobahns had a higher fatality rate than U.S. Interstates; however, a few years later, the Autobahn rate fell below that of (then) 55 mph (88 km/h) limited U.S. Interstates. IRTAD records show the U.S. rate remains higher than that on the largely unrestricted German Autobahn network. While the fatality rate on the UK's 70 mph (112 km/h) speed-limited motorways is about half of Germany's, the 60 mph (96 km/h) limit in rule-conscious Japan corresponds to a motorway fatality rate greater than Germany's. However, simple comparisons of fatality rates between countries neglect to account for differences in traffic density, quality of medical care, and Smeed's law. Roads without speed limits A few public roads still have no speed limit: Montana has had a speed limit since June 1999 - see the Montana section of the Speed limits in United States page for more information. See also | |||||||||||||||||
|
| ||||||||||||||||||
 |
|
| |