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Design Speed
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. Choosing a design speed means finding a balance between several interests which compete for priority, such high vehicle speeds to allow drivers to travel to their destinations quickly versus low vehicle speeds for the safety of people outside the vehicle (such as pedestrians and cyclists), or quick movement of peak traffic ( traffic engineering) versus maximising the economic development potential of the street (urban planning). Geometric features The design speed chosen for a high-speed roadway is a major factor in choosing superelevation rates and radii of curves, sight distance, and the lengths of crest and sag vertical curves. Roads with higher design speeds require wider lanes, sweeping curv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Road
A road is a linear way for the conveyance of traffic that mostly has an improved surface for use by vehicles (motorized and non-motorized) and pedestrians. Unlike streets, the main function of roads is transportation. There are many types of roads, including parkways, avenues, controlled-access highways (freeways, motorways, and expressways), tollways, interstates, highways, thoroughfares, and local roads. The primary features of roads include lanes, sidewalks (pavement), roadways (carriageways), medians, shoulders, verges, bike paths (cycle paths), and shared-use paths. Definitions Historically many roads were simply recognizable routes without any formal construction or some maintenance. The Organization for Economic Co-operation and Development (OECD) defines a road as "a line of communication (travelled way) using a stabilized base other than rails or air strips open to public traffic, primarily for the use of road motor vehicles running on their own wheels", ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geometric Design Of Roads
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. Geometric roadway design can be broken into three main parts: alignment, profile, and cross-section. Combined, they provide a three-dimensional layout for a roadway. The alignment is the route of the road, defined as a series of horizontal tangents and curves. The profile is the vertical aspect of the r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solomon Curve
] The Solomon curve is a graphical representation of the collision rate of automobiles as a function of their speed compared to the average vehicle speed on the same road. The curve was based on research conducted by David Solomon in the late 1950s and published in 1964. Subsequent research suggests significant biases in the Solomon study, which may cast doubt on its findings. The original research In 1964, Solomon researched the relationship between average speed and the collision rates of automobiles and plotted the results. While others have attempted to quantify the relationship between average speed and collision rates, Solomon's work was both "the earliest and best known". Solomon conducted a comprehensive study of more than 10,000 collision-involved drivers and their vehicles and how other roadway, driver, and vehicle characteristics affect the probability of being involved in a crash. He found that the probability of being involved in a crash per vehicle-mile as a funct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operating Speed
The operating speed of a road is the speed at which motor vehicles generally operate on that road. The precise definition of "operating speed", however, is open to debate. Some sources, such as the AASHTO, have changed their definitions recently to match the common use of the word. In 1994, the AASHTO ''Green Book'' defined the operating speed as "the highest overall speed at which a driver can travel on a given highway under favorable weather conditions and under prevailing traffic conditions without at any time exceeding the safe speed as determined by the design speed on a section-by-section basis," a definition which a majority of US states still use. In July 2001, however, the AASHTO revised their definition for the new edition of the ''Green Book'' and defined it as "the speed at which drivers are observed operating their vehicles during free-flow conditions." See also *Assured Clear Distance Ahead * Design speed * Solomon curve *Speed limit *Traffic psychology Traffi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Assured Clear Distance Ahead
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 re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Functional Classification
The functional classification of a road is the class or group of roads to which the road belongs. There are three main functional classes as defined by the United States Federal Highway Administration The Federal Highway Administration (FHWA) is a division of the United States Department of Transportation that specializes in highway transportation. The agency's major activities are grouped into two programs, the Federal-aid Highway Program ...: arterial, collector, and local. Arterial roads Arterial roads generally provide the fastest method of travel and typically have low accessibility from neighboring roads. They are usually designed with long-distance travel in mind and are not as common as the other two functional classes of roads. Examples include interstates and highways. Collector roads Collector roads are the second most common and are used as a connection between local roads and arterial roads. They provide a balance between access and mobility. Local ro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operating Speed
The operating speed of a road is the speed at which motor vehicles generally operate on that road. The precise definition of "operating speed", however, is open to debate. Some sources, such as the AASHTO, have changed their definitions recently to match the common use of the word. In 1994, the AASHTO ''Green Book'' defined the operating speed as "the highest overall speed at which a driver can travel on a given highway under favorable weather conditions and under prevailing traffic conditions without at any time exceeding the safe speed as determined by the design speed on a section-by-section basis," a definition which a majority of US states still use. In July 2001, however, the AASHTO revised their definition for the new edition of the ''Green Book'' and defined it as "the speed at which drivers are observed operating their vehicles during free-flow conditions." See also *Assured Clear Distance Ahead * Design speed * Solomon curve *Speed limit *Traffic psychology Traffi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territories, nine Minor Outlying Islands, and 326 Indian reservations. The United States is also in free association with three Pacific Island sovereign states: the Federated States of Micronesia, the Marshall Islands, and the Republic of Palau. It is the world's third-largest country by both land and total area. It shares land borders with Canada to its north and with Mexico to its south and has maritime borders with the Bahamas, Cuba, Russia, and other nations. With a population of over 333 million, it is the most populous country in the Americas and the third most populous in the world. The national capital of the United States is Washington, D.C. and its most populous city and principal financial center is New York City. Paleo-Americ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charles Marohn
Charles Marohn (born 1973) is an American author, land-use planner, municipal engineer, and the founder and president of Strong Towns, an organization which advocates for the development of dense towns and the restructuring of suburbia. Early life and education Charles L. Marohn Jr grew up in Baxter, Minnesota on a small farm. He graduated from Brainerd High School in 1991. Marohn received a Bachelor of Science in Civil Engineering and a Masters in Urban and Regional Planning from the University of Minnesota. In 2000 he became a licensed civil engineer in the state of Minnesota, but he has since faced scrutiny by the state licensing board after an engineer from South Dakota reported Marohn after failing to renew his license, yet still titling himself as an engineer. Marohn viewed this action as a limitation upon his first amendment rights because of his critical statements made about the practice of traffic engineering as well as his disapproval of civil engineers that he vi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Advisory Speed Limit
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'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Motor Vehicle
A motor vehicle, also known as motorized vehicle or automotive vehicle, is a self-propelled land vehicle, commonly wheeled, that does not operate on rails (such as trains or trams) and is used for the transportation of people or cargo. The vehicle propulsion is provided by an engine or motor, usually an internal combustion engine or an electric motor, or some combination of the two, such as hybrid electric vehicles and plug-in hybrids. For legal purpose, motor vehicles are often identified within a number of vehicle classes including cars, buses, motorcycles, off-road vehicles, light trucks and regular trucks. These classifications vary according to the legal codes of each country. ISO 3833:1977 is the standard for road vehicle types, terms and definitions. Generally, to avoid requiring people with disabilities from having to possess an operator's license to use one, or requiring tags and insurance, powered wheelchairs will be specifically excluded by law from being c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
