Map Speed Limit

[Deb Cartelli]

Speedlimits on road traffic, as used in most countries, set the legal maximum speed at which vehicles may travel on a given stretch of road.[1] Speed limits are generally indicated on a traffic sign reflecting the maximum permitted speed, expressed as kilometres per hour (km/h) or miles per hour (mph) or both. 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 Autobahnen in Germany.[2]

There are several reasons to regulate speed on roads. It is often done in an attempt to improve road traffic safety and to reduce the number of casualties from traffic collisions. The World Health Organization (WHO) identified speed control as one of a number of steps that can be taken to reduce road casualties.[n 1] As of 2021, the WHO estimates that approximately 1.3 million people die of road traffic crashes each year.[7]

Authorities may also set speed limits to reduce the environmental impact of road traffic (vehicle noise, vibration, emissions) or to enhance the safety of pedestrians, cyclists, and other road-users. For example, a draft proposal from Germany's National Platform on the Future of Mobility task force recommended a blanket 130 km/h (81 mph) speed limit across the Autobahnen to curb fuel consumption and carbon emissions.[8] Some cities have reduced limits to as little as 30 km/h (19 mph) for both safety and efficiency reasons.[9] However, some research indicates that changes in the speed limit may not always alter average vehicle speed.[10]Lower speed limits could reduce the use of over-engineered vehicles.[11]

In Western cultures, speed limits predate the use of motorized vehicles. In 1652, the American colony of New Amsterdam passed a law stating, "No wagons, carts or sleighs shall be run, rode or driven at a gallop". The punishment for breaking the law was "two pounds Flemish", the equivalent of US $50 in 2019.[12] The 1832 Stage Carriage Act introduced the offense of endangering the safety of a passenger or person by "furious driving" in the United Kingdom (UK).[13] In 1872, then-President of the United States Ulysses S. Grant was arrested for speeding in his horse-drawn carriage in Washington, D.C.[14][15]

On 28 January 1896, the first person to be convicted of speeding is believed to be Walter Arnold of East Peckham, Kent, UK, who was fined 1 shilling plus costs for speeding at 8 mph (13 km/h).[17][18][19]

In 1901, Connecticut was the first state in the United States to impose a numerical speed limit for motor vehicles, setting the maximum legal speed to 12 mph (19 km/h) in cities and 15 mph (24 km/h) on rural roads. Speed limits then propagated across the United States; by 1930 all but 12 states had established numerical limits.[12]

In Australia, during the early 20th century, there were people reported for "furious driving" offenses. One conviction in 1905 cited a vehicle furiously driving 20 mph (32 km/h) when passing a tram traveling at half that speed.[22]

In 2010, Sweden defined the Vision Zero program,[23] a multi-national road traffic safety project that aims to achieve a highway system with no fatalities or serious injuries involving road traffic.

Every driver of a vehicle shall in all circumstances have his vehicle under control to be able to exercise due and proper care and to be at all times in a position to perform all manœuvres required of him. He shall, when adjusting the speed of his vehicle, pay constant regard to the circumstances, in particular the lie of the land, the state of the road, the condition and load of his vehicle, the weather conditions and the density of traffic, so as to be able to stop his vehicle within his range of forward vision and short of any foreseeable obstruction. He shall slow down and if necessary stop whenever circumstances so require, and particularly when visibility is not excellent.

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.

In the United States, this requirement is referred to as the basic rule,[34] as outlined by US federal government law (49 CFR 392.14[35]), which applies in all states as permitted under the commerce clause and due process clause.[36][37] The basic speed law is almost always supplemented by specific maximum or minimum limits but applies regardless. In California, for instance, Vehicle Code section 22350 states that "No person shall drive a vehicle upon a highway at speed greater than is reasonable... and in no event at a speed which endangers the safety of persons or property".[38] The reasonable speed may be different than the posted speed limit. Basic rule speed laws are statutory reinforcements of the centuries-old common law negligence doctrine as specifically applied to vehicular speed.[39] Citations for violations of the basic speed law without a crash[40] have sometimes been ruled unfairly vague or arbitrary, hence a violation of the due process of law, at least in the State of Montana.[41] Even within states, differing jurisdictions (counties and cities) choose to prosecute similar cases with differing approaches.[42]

Consequential results of basic law violations are often categorized as excessive speed crashes; for example, the leading cause of crashes on German autobahns in 2012 fell into that category: 6,587 so-called "speed related" crashes claimed the lives of 179 people, which represented almost half (46.3%) of 387 autobahn fatalities in 2012.[43] However, "excessive speed" does not necessarily mean the speed limit was exceeded, rather that police determined at least one party traveled too fast for existing conditions.[43][44][45] Examples of conditions where drivers may find themselves driving too fast include wet roadways (due to rain, snow, or ice), reduced visibility (due to fog[46] or "white out" snow[47]), uneven roads, construction zones,[48] curves,[49] intersections, gravel roads,[50] and heavy traffic.[51] Per distance traveled, consequences of inappropriate speed are more frequent on lower speed, lower quality roads;[52] in the United States, for example, the "speeding fatality rate for local roads is three times that for Interstates".[53]

For speed management, a distinction can exist between excess speed, which consists of driving in excess of the speed limit, and inappropriate speed, which consists of going too fast for the conditions.[54]

Most countries have a legally assigned numerical maximum speed limit which applies on all roads when no other speed limit indications are present; lower speed limits are often shown on a sign at the start of the restricted section, although the presence of streetlights or the physical arrangement of the road may sometimes also be used instead. A posted speed limit may only apply to that road or to all roads beyond the sign that defines them depending on local laws.

The speed limit is commonly set at or below the 85th percentile speed (the operating speed which no more than 15% of traffic exceeds),[55][56][57] and in the US is frequently set 4 to 8 mph (6 to 13 km/h) below that speed.[58] Thus, if the 85th percentile operating speed as measured by a "Traffic and Engineering Survey" exceeds the design speed, legal protection is given to motorists traveling at such speeds (design speed is "based on conservative assumptions about the driver, the vehicle, and roadway characteristics").[59] The theory behind the 85th percentile rules is that, as a policy, most citizens should be deemed reasonable and prudent, and limits must be practical to enforce.[60][61] However, there are some circumstances where motorists do not tend to process all the risks involved, and as a mass, choose a poor 85th percentile speed.[citation needed] This rule, in practice, is a process for "voting the speed limit" by driving, in contrast to delegating the speed limit to an engineering expert.[62][63]

The maximum speed permitted by statute, as posted, is normally based on ideal driving conditions and the basic speed rule always applies.[64] Violation of the statute generally raises a rebuttable presumption of negligence.[65]

Some roads also have minimum speed limits, usually where slow speeds can impede traffic flow or be dangerous.[66] The use of minimum speed limits is not as common as maximum speed limits, since the risks of speed are less common at lower speeds.[23] In some jurisdictions, laws requiring a minimum speed are primarily centered around red-light districts or similar areas, where they may colloquially be referred to as kerb crawling laws.[67]

In Germany, the first known experiments with variable speed limit signs took place in 1965 on a 30-kilometre (19 mi) stretch of German motorway, the A8 between Munich and the border city of Salzburg, Austria. Mechanically variable message signs could display speeds of 60, 80 and 100 km/h, as well as text indicating a "danger zone" or "accident". Personnel monitored traffic using video technology and manually controlled the signage.[69] Beginning in the 1970s, additional advanced traffic control systems were put into service. Modern motorway control systems can work without human intervention using various types of sensors to measure traffic flow and weather conditions. In 2009, 1,300 kilometres (810 mi) of German motorways were equipped with such systems.[70]

In the United States, heavily traveled portions of the New Jersey Turnpike began using variable speed limit signs in combination with variable message signs in the late 1960s. Officials can adjust the speed limit according to weather, traffic conditions, and construction.[71] More typically, variable speed limits are used on remote stretches of highway in the United States in areas with extreme changes in driving conditions.[72] For example, variable limits were introduced in October 2010 on a 52-mile (84 km) stretch of Interstate 80 in Wyoming, replacing the winter season speed reduction from 75 to 65 mph (121 to 105 km/h) that had been in place since 2008.[73][74] This Variable Speed Limit system has been proven effective in terms of reducing crash frequency and road closures.[75][76] Similarly, Interstate 90 at Snoqualmie Pass and other mountain passes in Washington State have variable speed limits as to slow traffic in severe winter weather.[72][77] As a response to fog-induced chain-reaction collisions involving 99 vehicles in 1990, a variable speed limit system covering 19 miles (31 km) of Interstate 75 in Tennessee was implemented in fog-prone areas around the Hiwassee River.[78] The Georgia Department of Transportation installed variable speed limits on part of Interstate 285 around Atlanta in 2014. These speeds can be as low as 35 mph (56 km/h) but are generally set to 35 mph (56 km/h).[79] In 2016, the Oregon Department of Transportation installed a variable speed zone on a 30 mi (48 km) stretch of Interstate 84 between Baker City and Ladd Canyon. The new electronic signs collect data regarding temperature, skid resistance, and average motorist speed to determine the most effective speed limit for the area before presenting the limit on the sign. This speed zone was scheduled to be activated November 2016.[citation needed] Ohio established variable speed limits on three highways in 2017, then in 2019 granted the authority to the Ohio Department of Transportation to establish variable limits on any of its highways.[80][81]

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