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Traffic comprises pedestrians, vehicles, ridden or herded animals, trains, and other conveyances that use public ways (roads/sidewalks) for travel and transportation.
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.
Traffic lights, traffic signals, or stoplights – also known as robots in South Africa and Namibia – are signalling devices positioned at road intersections, pedestrian crossings, and other locations in order to control the flow of traffic.
Traffic calming uses physical design and other measures to improve safety for motorists, car drivers, pedestrians and cyclists. It has become a tool to combat speeding and other unsafe behaviours of drivers. It aims to encourage safer, more responsible driving and potentially reduce traffic flow. Urban planners and traffic engineers have many strategies for traffic calming, including narrowed roads and speed humps. Such measures are common in Australia and Europe, but less so in North America. Traffic calming is a calque of the German word Verkehrsberuhigung – the term's first published use in English was in 1985 by Carmen Hass-Klau.
Traffic signs or road signs are signs erected at the side of or above roads to give instructions or provide information to road users. The earliest signs were simple wooden or stone milestones. Later, signs with directional arms were introduced, for example the fingerposts in the United Kingdom and their wooden counterparts in Saxony.
Road traffic safety refers to the methods and measures used to prevent road users from being killed or seriously injured. Typical road users include pedestrians, cyclists, motorists, vehicle passengers, and passengers of on-road public transport.
In statistics, a k-thpercentile, also known as percentile score or centile, is a score below which a given percentage k of scores in its frequency distribution falls or a score at or below which a given percentage falls. Percentiles are expressed in the same unit of measurement as the input scores, not in percent; for example, if the scores refer to human weight, the corresponding percentiles will be expressed in kilograms or pounds. In the limit of an infinite sample size, the percentile approximates the percentile function, the inverse of the cumulative distribution function.
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.
The Manual on Uniform Traffic Control Devices for Streets and Highways is a document issued by the Federal Highway Administration (FHWA) of the United States Department of Transportation (USDOT) to specify the standards by which traffic signs, road surface markings, and signals are designed, installed, and used. In the United States, all traffic control devices must legally conform to these standards. The manual is used by state and local agencies as well as private construction firms to ensure that the traffic control devices they use conform to the national standard. While some state agencies have developed their own sets of standards, including their own MUTCDs, these must substantially conform to the federal MUTCD.
Transportation safety in the United States encompasses safety of transportation in the United States, including automobile crashes, airplane crashes, rail crashes, and other mass transit incidents, although the most fatalities are generated by road incidents annually killing 32,479 people in 2011 to over 42,000 people in 2022. The number of deaths per passenger-mile on commercial airlines in the United States between 2000 and 2010 was about 0.2 deaths per 10 billion passenger-miles. For driving, the rate was 150 per 10 billion vehicle-miles: 750 times higher per mile than for flying in a commercial airplane.
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.
A radar speed sign or speed feedback sign is an interactive sign comprising a speed-measuring device and a message sign generally constructed of a series of LEDs, which displays vehicle speed of approaching motorists. The purpose of radar speed signs is to slow cars down by making drivers aware when they are driving at speeds above the posted limits. They are used as a traffic calming device in addition to or instead of physical devices such as speed bumps and rumble strips.
The design speed is a tool used to determine geometric features of a new road or street during road design. Contrary to the word's implication, the design speed of the road or street is not necessarily its vehicle speed limit or maximum safe speed; that can be higher or lower.
86 percent of people in the United States use private automobiles as their primary form of transportation to their workplace.
In road design, a slip lane is a road at a junction that allows road users to change roads without actually entering an intersection. Slip lanes are "helpful ...for intersections designed for large buses or trucks to physically make a turn in the space allotted, or where the right turn is sharper than a 90 degree turn." Slip lanes may reduce congestion and "t-bone" motor vehicle collisions, but they increase the risk for pedestrians, cyclists and horse riders who cross the slip lane.
A traffic collision, also known as a motor vehicle collision, occurs when a vehicle collides with another vehicle, pedestrian, animal, road debris, or other moving or stationary obstruction, such as a tree, pole or building. Traffic collisions often result in injury, disability, death, and property damage as well as financial costs to both society and the individuals involved. Road transport is statistically the most dangerous situation people deal with on a daily basis, but casualty figures from such incidents attract less media attention than other, less frequent types of tragedy. The commonly used term car accident is increasingly falling out of favor with many government departments and organizations, with the Associated Press style guide recommending caution before using the term. Some collisions are intentional vehicle-ramming attacks, staged crashes, vehicular homicide or vehicular suicide.
The normal function of traffic lights requires more than sight control and coordination to ensure that traffic and pedestrians move as smoothly, and safely as possible. A variety of different control systems are used to accomplish this, ranging from simple clockwork mechanisms to sophisticated computerized control and coordination systems that self-adjust to minimize delay to people using the junction.
The geometric design of roads is the branch of highway engineering concerned with the positioning of the physical elements of the roadway according to standards and constraints. The basic objectives in geometric design are to optimize efficiency and safety while minimizing cost and environmental damage. Geometric design also affects an emerging fifth objective called "livability," which is defined as designing roads to foster broader community goals, including providing access to employment, schools, businesses and residences, accommodate a range of travel modes such as walking, bicycling, transit, and automobiles, and minimizing fuel use, emissions and environmental damage.
Road speed limits in the United Kingdom are used to define the maximum legal speed for vehicles using public roads in the UK.
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.
References
- ↑ Taylor, Brian D.; Hong Hwang, Yu (June 30, 2020). "Eighty-Five Percent Solution: Historical Look at Crowdsourcing Speed Limits and the Question of Safety". Transportation Research Record. 2674 (9): 346–357. doi:10.1177/0361198120928995 . Retrieved May 25, 2024.
- 1 2 3 4 Tchir, Jason (May 30, 2021). "Shouldn't speed limits be designed for the '85th percentile' of drivers?". The Globe and Mail . Archived from the original on June 2, 2021. Retrieved May 15, 2024.
The 85th percentile is an old tool for setting speeds on new roads, experts say – but it doesn't mean all limits should be decided by the fast crowd. 'It's got a history that goes back 50-plus years,' said Jeff Lindley, chief technical officer for the Institute of Transportation Engineers (ITE). 'Over the years, I would say there has been an overreliance on [the 85th percentile] as a way to set and adjust speed limits in a way that wasn't intended.'
- ↑ McKinley, Jesse (March 23, 2023). "Is 70 M.P.H. the New 65? Legislators Say N.Y. Roads Are Just Too Slow". The New York Times . Retrieved September 15, 2023.
States set speed limits using a variety of methods and measurements, including the so-called 85 percentile rule, which refers to the speed 'at or below which 85 percent of the drivers travel on a road segment', according to the Federal Highway Administration.
- 1 2 3 4 Minor, Nathaniel (September 15, 2023). "A lower speed limit could be coming to a Colorado road near you". Colorado Public Radio . Retrieved September 15, 2023.
Traditionally, U.S. traffic engineers use the '85th percentile' method that sets limits at the speed at or below which 85 percent of drivers travel in normal conditions. This federally approved approach has been used by state and local transportation agencies since at least the '60s, but street safety advocates and city transportation officials deride the method because it usually leads to higher speed limits and faster speeds, which is associated with more serious crashes.
- ↑ "Setting Speed Limits". Institute of Transportation Engineers. Retrieved January 18, 2024.
- 1 2 Sánchez, Vanessa G. (May 25, 2024). Written at Los Angeles. "'So Much Death': Lawmakers Weigh Stricter Speed Limits, Safer Roads for Pedestrians". U.S. News & World Report . Washington, D.C. KFF Health News . Retrieved May 25, 2024.
Road safety advocates argue the federal government missed an opportunity to eliminate outdated standards for setting speed limits when it revised traffic guidelines last year. The agency could have eliminated guidance recommending setting speed limits at or below how fast 85% of drivers travel on uncongested roads. Critics contend that what's known as the 85th percentile rule encourages traffic engineers to set speed limits at levels unsafe for pedestrians.
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