Speed limit in the context of Road safety

Road traffic safety refers to the methods and measures, such as traffic calming, to prevent road users from being killed or seriously injured. Typical road users include pedestrians, cyclists, motorists, passengers of vehicles, and passengers of on-road public transport, mainly buses and trams.

Best practices in modern road safety strategy:

An emergency vehicle is a vehicle used by emergency services. Emergency vehicles typically have specialized emergency lighting and vehicle equipment that allow emergency services to reach calls for service in a timely manner, transport equipment and resources, or perform their tasks efficiently. Emergency vehicles are usually operated by authorized government agencies, but some may also be operated by private entities where permitted by law.

Emergency vehicles are usually given right of way in traffic, and may be exempted from certain basic road laws to reach their destinations in the fastest possible time, such as driving through a red traffic light or exceeding the speed limit; however, this is almost always done with emergency lights and sirens on, to alert traffic that the emergency vehicle is approaching. In some jurisdictions, the driver of an emergency vehicle can face legal action if the driver shows "reckless disregard for the safety of others".

An arterial road or arterial thoroughfare is a high-capacity urban road that sits below highways on the road hierarchy in terms of traffic flow and speed. The primary function of an arterial road is to deliver traffic from collector roads to highways or expressways, and between urban hubs at a relatively high level of service. Therefore, many arteries are limited-access roads or feature restrictions on private access. Because of their relatively high accessibility, many major roads face large amounts of land use and urban development, making them significant urban places.

In traffic engineering hierarchy, an arterial road delivers traffic between collector roads and highways. For new arterial roads, intersections are often reduced to increase traffic flow. In California, arterial roads are usually spaced every half mile, and have intersecting collector(s) and streets.

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 centres 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.

The Autobahn (IPA: [ˈaʊtoˌbaːn] ; German pl. Autobahnen, pronounced [ˈaʊtoˌbaːnən] ) is the federal controlled-access highway system in Germany. The official term is Bundesautobahn (abbreviated BAB), which translates as 'federal motorway'. The literal meaning of the word Bundesautobahn is 'Federal Auto(mobile) Track'.

Much of the system has no speed limit for some classes of vehicles. However, limits are posted and enforced in areas that are urbanised, substandard, prone to collisions, or under construction. On speed-unrestricted stretches, an advisory speed limit (Richtgeschwindigkeit) of 130 kilometres per hour (81 mph) applies. While driving faster is not illegal in the absence of a speed limit, it can cause an increased liability in the case of a collision (which mandatory auto insurance has to cover); courts have ruled that an "ideal driver" who is exempt from absolute liability for "inevitable" tort under the law would not exceed the advisory speed limit.

A variable- (also changeable-, electronic-, or dynamic-) message sign or message board, often abbreviated VMS, VMB, 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.

The George Washington Bridge is a double-decked suspension bridge spanning the Hudson River, connecting Fort Lee in Bergen County, New Jersey, with the Washington Heights neighborhood of Manhattan, New York City. It is named after George Washington, a Founding Father of the United States and the country's first president. The George Washington Bridge is the world's busiest motor vehicle bridge, carrying a traffic volume of over 104 million vehicles in 2019, and is the world's only suspension bridge with 14 vehicular lanes. The George Washington Bridge measures 4,760 feet (1,450 m) long, and its main span is 3,500 feet (1,100 m) long. It was the longest main bridge span in the world from its 1931 opening until the Golden Gate Bridge in San Francisco opened in 1937.

The bridge is informally known as the GW Bridge, the GWB, the GW, or the George, and was known as the Fort Lee Bridge or Hudson River Bridge during construction. It is owned by the Port Authority of New York and New Jersey, a bi-state government agency that operates infrastructure in the Port of New York and New Jersey. The George Washington Bridge is an important travel corridor within the New York metropolitan area. It has an upper level that carries four lanes in each direction and a lower level with three lanes in each direction, for a total of 14 lanes of travel. The speed limit on the bridge is 45 mph (72 km/h). The bridge's upper level also carries pedestrian and bicycle traffic. Interstate 95 (I-95) and U.S. Route 1/9 (US 1/9, composed of US 1 and US 9) cross the river via the bridge. U.S. Route 46 (US 46), which lies entirely within New Jersey, terminates halfway across the bridge at the state border with New York. At its eastern terminus in New York City, the bridge continues onto the Trans-Manhattan Expressway (part of I-95, connecting to the Cross Bronx Expressway).

A dual carriageway (BrE) or a divided highway (AmE) is a class of highway with carriageways for traffic travelling in opposite directions separated by a central reservation (BrE) or median (AmE). 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.

A road without a central reservation is known as a single carriageway regardless of how many lanes there are. Dual carriageways have improved road traffic safety over the years and over single carriageways and typically have higher speed limits as a result. In some places, express lanes and local or collector lanes are used within a local-express-lane system to provide more capacity and to smooth out traffic flows for longer-distance travel.

The 400-series highways are a network of controlled-access highways in the Canadian province of Ontario, forming a special subset of the provincial highway system. They are analogous to the Interstate Highway System in the United States or the Autoroute system of neighbouring Quebec, and are regulated by the Ministry of Transportation of Ontario (MTO). The 400-series designations were introduced in 1952, although Ontario had been constructing divided highways for two decades prior. Initially, only Highways 400, 401 and 402 were numbered; other designations followed in the subsequent decades. To this day, not all controlled-access highways in Ontario are a part of the 400-series highway network. The network is situated almost entirely in Southern Ontario, although Highway 400 extends into the more remote northern portion of the province.

Modern 400-series highways have high design standards, speed limits of 100 kilometres per hour (62 mph), with a 110 kilometres per hour (68 mph) limit on select stretches, and various collision avoidance and traffic management systems. The design of 400-series highways has set the precedent for a number of innovations used throughout North America, including the parclo interchange and a modified Jersey barrier design known as the Ontario Tall Wall. As a result, they currently experience one of the lowest accident and fatality rates comparative to traffic volume in North America.

Speed limits are enforced on most public roadways by authorities, with the purpose to improve driver compliance with speed limits. Methods used include roadside speed traps set up and operated by the police and automated roadside "speed camera" systems, which may incorporate the use of an automatic number plate recognition system. Traditionally, police officers used stopwatches to measure the time taken for a vehicle to cover a known distance. More recently, radar guns and automated in-vehicle systems have come into use.

A worldwide review of studies found that speed cameras led to a reduction of "11% to 44% for fatal and serious injury crashes". The UK Department for Transport estimated that cameras had led to a 22% reduction in personal injury collisions and 42% fewer people being killed or seriously injured at camera sites. The British Medical Journal recently reported that speed cameras were effective at reducing accidents and injuries in their vicinity and recommended wider deployment. An LSE study in 2017 found that "adding another 1,000 cameras to British roads could save up to 190 lives annually, reduce up to 1,130 collisions and mitigate 330 serious injuries."

In legal terminology, the assured clear distance ahead (ACDA) is the distance ahead of any terrestrial locomotive device such as a land vehicle, typically an automobile, or watercraft, within which they should be able to bring the device to a halt. It is one of the most fundamental principles governing ordinary care and the duty of care for all methods of conveyance, and is frequently used to determine if a driver is in proper control and is a nearly universally implicit consideration in vehicular accident liability. The rule is a precautionary trivial burden required to avert the great probable gravity of precious life loss and momentous damage. Satisfying the ACDA rule is necessary but not sufficient to comply with the more generalized basic speed law, and accordingly, it may be used as both a layman's criterion and judicial test for courts to use in determining if a particular speed is negligent, but not to prove it is safe. As a spatial standard of care, it also serves as required explicit and fair notice of prohibited conduct so unsafe speed laws are not void for vagueness. The concept has transcended into accident reconstruction and engineering.

This distance is typically both determined and constrained by the proximate edge of clear visibility, but it may be attenuated to a margin of which beyond hazards may reasonably be expected to spontaneously appear. The rule is the specific spatial case of the common law basic speed rule, and an application of volenti non fit injuria. The two-second rule may be the limiting factor governing the ACDA, when the speed of forward traffic is what limits the basic safe speed, and a primary hazard of collision could result from following any closer.

Speed bumps (also called traffic thresholds, speed breakers or sleeping policemen) are a class of traffic calming devices that use vertical deflection to slow motor-vehicle traffic in order to improve safety conditions. Variations include the speed hump, speed cushion, and speed table.

The use of vertical deflection devices is widespread around the world, and they are most commonly used to enforce a speed limit under 40 km/h (25 mph).

Active traffic management (also managed lanes, smart lanes, managed/smart motorways) is a method of increasing peak capacity and smoothing traffic flows on busy major highways. Techniques include variable speed limits, hard-shoulder running and ramp-metering controlled by overhead variable message signs. It has been implemented in several countries, including Germany, the United Kingdom, Canada and the United States.

A traffic ticket is a notice issued by a law enforcement official to a motorist or other road user, indicating that the user has violated traffic laws. Traffic tickets generally come in two forms, citing a moving violation, such as exceeding the speed limit, or a non-moving violation, such as a parking violation, with the ticket also being referred to as a parking citation, or parking ticket.

In some jurisdictions, a traffic ticket constitutes a notice that a penalty, such as a fine or accumulation of “points”, has been or will be assessed against the driver or owner of a vehicle; failure to pay generally leads to prosecution or to civil recovery proceedings for the fine. In others, the ticket constitutes only a citation and summons to appear at traffic court, with a determination of guilt to be made only in court.