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Traffic Flow
In transportation engineering, traffic flow is the study of interactions between travellers (including pedestrians, cyclists, drivers, and their vehicles) and infrastructure (including highways, signage, and traffic control devices), with the aim of understanding and developing an optimal transport network with efficient movement of traffic and minimal traffic congestion problems. The foundation for modern traffic flow analysis dates back to the 1920s with Frank Knight's analysis of traffic equilibrium, further developed by John Glen Wardrop, Wardrop in 1952. Despite advances in computing, a universally satisfactory theory applicable to real-world conditions remains elusive. Current models blend empirical and theoretical techniques to forecast traffic and identify congestion areas, considering variables like vehicle use and land changes. Traffic flow is influenced by the Complex system, complex interactions of vehicles, displaying behaviors such as cluster formation and shock wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Traffic Flow (computer Networking)
In packet switching networks, traffic flow, packet flow or ''network flow'' is a sequence of packets from a source computer to a destination, which may be another host, a multicast group, or a broadcast domain. RFC 2722 defines traffic flow as "an artificial logical equivalent to a call or connection." RFC 3697 defines traffic flow as "a sequence of packets sent from a particular source to a particular unicast, anycast, or multicast destination that the source desires to label as a flow. A flow could consist of all packets in a specific transport connection or a media stream. However, a flow is not necessarily 1:1 mapped to a transport connection." Flow is also defined in RFC 3917 as "a set of IP packets passing an observation point in the network during a certain time interval." Packet flow temporal efficiency can be affected by one-way delay (OWD) that is described as a combination of the following components: * Processing delay (the time taken to process a packet in a netw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Empirical
Empirical evidence is evidence obtained through sense experience or experimental procedure. It is of central importance to the sciences and plays a role in various other fields, like epistemology and law. There is no general agreement on how the terms ''evidence'' and ''empirical'' are to be defined. Often different fields work with quite different conceptions. In epistemology, evidence is what justifies beliefs or what determines whether holding a certain belief is rational. This is only possible if the evidence is possessed by the person, which has prompted various epistemologists to conceive evidence as private mental states like experiences or other beliefs. In philosophy of science, on the other hand, evidence is understood as that which '' confirms'' or ''disconfirms'' scientific hypotheses and arbitrates between competing theories. For this role, evidence must be public and uncontroversial, like observable physical objects or events and unlike private mental states, so ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mass Flow Rate
In physics and engineering, mass flow rate is the Temporal rate, rate at which mass of a substance changes over time. Its unit of measurement, unit is kilogram per second (kg/s) in SI units, and Slug (unit), slug per second or pound (mass), pound per second in US customary units. The common symbol is \dot (pronounced "m-dot"), although sometimes \mu (Greek language, Greek lowercase Mu (letter), mu) is used. Sometimes, mass flow rate as defined here is termed "mass flux" or "mass current". Confusingly, "mass flow" is also a term for mass flux, the rate of mass flow per unit of area. Formulation Mass flow rate is defined by the limit of a function, limit \dot = \lim_ \frac = \frac, i.e., the flow of mass \Delta m through a surface per time \Delta t. The overdot on \dot is Newton's notation for a time derivative. Since mass is a scalar (physics), scalar quantity, the mass flow rate (the time derivative of mass) is also a scalar quantity. The change in mass is the amount that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vertical Queue
The concept of a vertical queue is often used in traffic flow studies as a common assumption to simplify analysis problems. Its use enables many calculations to be simplified, allowing researchers to get to the core of their problem, while ignoring the effects of queue buildup on a roadway. Vertical queues can also be used in traffic signal analysis, with vertical queues occurring at the location of the stop bar. Concept usage The vertical queue assumption presumes that vehicles on a roadway do not back up over the length of the roadway, which would be considered a horizontal queue, but rather stack up upon one another at the point where congestion begins or at the stop line of a traffic signal. The vertical queue is unitless, and is simply representative of the number of vehicles which are delayed at a given point in a system. This is clearly not possible in real life, but the assumption allows vehicles in an analysis Analysis (: analyses) is the process of breaking ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Density
Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be used: \rho = \frac, where ''ρ'' is the density, ''m'' is the mass, and ''V'' is the volume. In some cases (for instance, in the United States oil and gas industry), density is loosely defined as its weight per unit volume, although this is scientifically inaccurate this quantity is more specifically called specific weight. For a pure substance, the density is equal to its mass concentration. Different materials usually have different densities, and density may be relevant to buoyancy, purity and packaging. Osmium is the densest known element at standard conditions for temperature and pressure. To simplify comparisons of density across different systems of units, it is sometimes replaced by the dimensionless quantity "relative den ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Structure Formation
In physical cosmology, structure formation describes the creation of galaxies, galaxy clusters, and larger structures starting from small fluctuations in mass density resulting from processes that created matter. The universe, as is now known from observations of the cosmic microwave background radiation, began in a hot, dense, nearly uniform state approximately 13.8 billion years ago. However, looking at the night sky today, structures on all scales can be seen, from stars and planets to galaxies. On even larger scales, galaxy clusters and sheet-like structures of galaxies are separated by enormous voids containing few galaxies. Structure formation models gravitational instability of small ripples in mass density to predict these shapes, confirming the consistency of the physical model. The modern Lambda-CDM model is successful at predicting the observed large-scale distribution of galaxies, clusters and voids; but on the scale of individual galaxies there are many complicatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clustering Of Self-propelled Particles
Many experimental realizations of self-propelled particles exhibit a strong tendency to aggregate and form clusters, whose dynamics are much richer than those of passive colloids. These aggregates of particles form for a variety of reasons, from chemical gradients to magnetic and ultrasonic fields. Self-propelled enzyme motors and synthetic nanomotors also exhibit clustering effects in the form of chemotaxis. Chemotaxis is a form of collective motion of biological or non-biological particles toward a fuel source or away from a threat, as observed experimentally in enzyme diffusion and also synthetic chemotaxis or phototaxis. In addition to irreversible schooling, self-propelled particles also display reversible collective motion, such as predator–prey behavior and oscillatory clustering and dispersion. Phenomenology This clustering behavior has been observed for self-propelled Janus particles, either platinum-coated gold particles or carbon-coated silica beads, and for magne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vehicle
A vehicle () is a machine designed for self-propulsion, usually to transport people, cargo, or both. The term "vehicle" typically refers to land vehicles such as human-powered land vehicle, human-powered vehicles (e.g. bicycles, tricycles, velomobiles), animal-powered transports (e.g. horse-drawn vehicle, horse-drawn carriages/wagons, ox carts, dog sleds), motor vehicles (e.g. motorcycles, cars, trucks, buses, mobility scooters) and rail transport, railed vehicles (trains, trams and monorails), but more broadly also includes cable transport (aerial lift, cable cars and elevators), watercraft (ships, boats and underwater vehicles), amphibious vehicles (e.g. screw-propelled vehicles, hovercraft, seaplanes), aircraft (airplanes, helicopters, glider (aircraft), gliders and aerostats) and space vehicles (spacecraft, spaceplanes and launch vehicles). This article primarily concerns the more ubiquitous land vehicles, which can be broadly classified by the type of contact interface with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Road Space Requirements
A road is a thoroughfare used primarily for movement of traffic. Roads differ from streets, whose primary use is local access. They also differ from stroads, which combine the features of streets and roads. Most modern roads are Road surface, paved. The words "road" and "street" are commonly considered to be interchangeable, but the distinction is important in urban design. There are road hierarchy, many types of roads, including parkways, avenue (landscape), avenues, controlled-access highways (freeways, motorways, and expressways), tollways, interstates, highways, and local roads. The primary features of roads include lanes, sidewalks (pavement), roadways (carriageways), median strip, medians, shoulder (road), shoulders, road verge, 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 Organisation for Economic Co-operation and Development, Organi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Passenger Capacity Of Different Transport Modes
A passenger is a person who travels in a vehicle, but does not bear any responsibility for the tasks required for that vehicle to arrive at its destination or otherwise operate the vehicle, and is not a steward. The vehicles may be bicycles, buses, cars, passenger trains, airliners, ships, ferryboats, personal watercraft, all terrain vehicles, snowmobiles, and other methods of transportation. Crew members (if any), as well as the driver or pilot of the vehicle, are usually not considered to be passengers. For example, a flight attendant on an airline would not be considered a passenger while on duty and the same with those working in the kitchen or restaurant on board a ship as well as cleaning staff, but an employee riding in a company car being driven by another person would be considered a passenger, even if the car was being driven on company business. Legal status In most jurisdictions, laws have been enacted that dictate the legal obligations of the owner of a v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Traffic Congestion
Traffic congestion is a condition in transport that is characterized by slower speeds, longer trip times, and increased vehicular queueing. Traffic congestion on urban road networks has increased substantially since the 1950s, resulting in many of the roads becoming obsolete. When traffic demand is great enough that the interaction between vehicles slows the traffic stream, this results in congestion. While congestion is a possibility for any mode of transportation, this article will focus on automobile congestion on public roads. Mathematically, traffic is modeled as a flow through a fixed point on the route, analogously to fluid dynamics. As demand approaches the capacity of a road (or of the intersections along the road), extreme traffic congestion sets in. When vehicles are fully stopped for periods of time, this is known as a traffic jam or (informally) a traffic snarl-up or a tailback. Drivers can become frustrated and engage in road rage. Drivers and driver-focused r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mode Of Transport
A mode of transport is a method or way of travelling, or of transporting people or cargo. The different modes of transport include air, water, and land transport, which includes rails or railways, road and off-road transport. Other modes of transport also exist, including pipelines, cable transport, and space transport. Human-powered transport and animal-powered transport are sometimes regarded as distinct modes, but they may lie in other categories such as land or water transport. In general, '' transportation'' refers to the moving of people, animals, and other goods from one place to another, and ''means of transport'' refers to the transport facilities used to carry people or cargo according to the chosen mode. Examples of the means of transport include automobile, airplane, ship, truck, and train. Each mode of transport has a fundamentally different set of technological solutions. Each mode has its own infrastructure, vehicles, transport operators and operations. An ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
