Speed limits on road traffic, as used in most countries, 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 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.
The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. At 20 °C (68 °F), the speed of sound in air is about 343 m/s, or one km in 2.91 s or one mile in 4.69 s. It depends strongly on temperature as well as the medium through which a sound wave is propagating. At 0 °C (32 °F), the speed of sound in air is about 331 m/s. More simply, the speed of sound is how fast vibrations travel.
Speed bumps 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.
A Formula One car or F1 car is a single-seat, open-cockpit, open-wheel formula racing car with substantial front and rear wings, and an engine positioned behind the driver, intended to be used in competition at Formula One racing events. The regulations governing the cars are unique to the championship and specify that cars must be constructed by the racing teams themselves, though the design and manufacture can be outsourced. Formula One cars are the fastest cars in the world around a race track, owing to very high cornering speeds achieved through the generation of large amounts of aerodynamic downforce. Due to the amount of braking force and the total cornering envelope of a Formula One car, Formula One drivers experience frequent lateral g-loadings in excess of five g and peak cornering forces of up to seven lateral g.
Linienzugbeeinflussung is a cab signalling and train protection system used on selected German and Austrian railway lines as well as on the AVE and some commuter rail lines in Spain. The system was mandatory where trains were allowed to exceed speeds of 160 km/h (99 mph) in Germany and 220 km/h (140 mph) in Spain. It is also used on some slower railway and urban rapid transit lines to increase capacity. The German Linienzugbeeinflussung translates to continuous train control, literally: linear train influencing. It is also called linienförmige Zugbeeinflussung.
The overconfidence effect is a well-established bias in which a person's subjective confidence in their judgments is reliably greater than the objective accuracy of those judgments, especially when confidence is relatively high. Overconfidence is one example of a miscalibration of subjective probabilities. Throughout the research literature, overconfidence has been defined in three distinct ways: (1) overestimation of one's actual performance; (2) overplacement of one's performance relative to others; and (3) overprecision in expressing unwarranted certainty in the accuracy of one's beliefs.
In the United States, speed limits are set by each state or territory. States have also allowed counties and municipalities to enact typically lower limits. Highway speed limits can range from an urban low of 25 mph (40 km/h) to a rural high of 85 mph (137 km/h). Speed limits are typically posted in increments of five miles per hour (8 km/h). Some states have lower limits for trucks, some also have night and/or minimum speed limits.
The kappa effect or perceptual time dilation is a temporal perceptual illusion that can arise when observers judge the elapsed time between sensory stimuli applied sequentially at different locations. In perceiving a sequence of consecutive stimuli, subjects tend to overestimate the elapsed time between two successive stimuli when the distance between the stimuli is sufficiently large, and to underestimate the elapsed time when the distance is sufficiently small.
Bicycle performance is measurable performance such as energy efficiency that affect how effective a bicycle is. Bicycles are extraordinarily efficient machines; in terms of the amount of energy a person must expend to travel a given distance, cycling is calculated to be the most efficient self-powered means of transportation.
The National Maximum Speed Limit (NMSL) was a provision of the federal government of the United States 1974 Emergency Highway Energy Conservation Act that effectively prohibited speed limits higher than 55 miles per hour (89 km/h). The limit was increased to 65 miles per hour (105 km/h) in 1987. It was drafted in response to oil price spikes and supply disruptions during the 1973 oil crisis. Even after fuel costs began to decrease over time the law would remain in place until 1995 as proponents claimed it reduced traffic fatalities.
Optimism bias is a cognitive bias that causes someone to believe that they themselves are less likely to experience a negative event. It is also known as unrealistic optimism or comparative optimism.
Braking distance refers to the distance a vehicle will travel from the point when its brakes are fully applied to when it comes to a complete stop. It is primarily affected by the original speed of the vehicle and the coefficient of friction between the tires and the road surface, and negligibly by the tires' rolling resistance and vehicle's air drag. The type of brake system in use only affects trucks and large mass vehicles, which cannot supply enough force to match the static frictional force.
In the study of path-finding problems in artificial intelligence, a heuristic function is said to be consistent, or monotone, if its estimate is always less than or equal to the estimated distance from any neighbouring vertex to the goal, plus the cost of reaching that neighbour.
Energy-efficient driving techniques are used by drivers who wish to reduce their fuel consumption, and thus maximize fuel efficiency. Many drivers have the potential to improve their fuel efficiency significantly. Simple things such as keeping tires properly inflated, having a vehicle well-maintained and avoiding idling can dramatically improve fuel efficiency. Careful use of acceleration and deceleration and especially limiting use of high speeds helps efficiency. The use of multiple such techniques is called "hypermiling".
In social psychology, illusory superiority is a cognitive bias wherein a person overestimates their own qualities and abilities compared to other people. Illusory superiority is one of many positive illusions, relating to the self, that are evident in the study of intelligence, the effective performance of tasks and tests, and the possession of desirable personal characteristics and personality traits. Overestimation of abilities compared to an objective measure is known as the overconfidence effect.
The well travelled road effect is a cognitive bias in which travellers will estimate the time taken to traverse routes differently depending on their familiarity with the route. Frequently travelled routes are assessed as taking a shorter time than unfamiliar routes. This effect creates errors when estimating the most efficient route to an unfamiliar destination, when one candidate route includes a familiar route, whilst the other candidate route includes no familiar routes. The effect is most salient when subjects are driving, but is still detectable for pedestrians and users of public transport. The effect has been observed for centuries but was first studied scientifically in the 1980s and 1990s following from earlier "heuristics and biases" work undertaken by Daniel Kahneman and Amos Tversky.
Road speed limits in the United Kingdom are used to define the maximum legal speed for vehicles using public roads in the UK.
French roads have a variable maximum speed limit that depends on weather conditions. In dry weather rural 2- or 3-lane roads are limited to 80 km/h, 4-lane expressways 110 km/h, and highways 130 km/h. When raining, the limits are respectively lowered to 80, 100, and 110 km/h. Urban speed limit of 50 km/h is unaffected by weather. The general speed limit is lowered to 50 km/h on all roads in the fog or other low-visibility conditions if visibility is under 50 metres.
The false-uniqueness effect is an attributional type of cognitive bias in social psychology that describes how people tend to view their qualities, traits, and personal attributes as unique when in reality they are not. This bias is often measured by looking at the difference between estimates that people make about how many of their peers share a certain trait or behaviour and the actual number of peers who report these traits and behaviours.
