|
Three-detector Problem And Newell's Method
The Three-detector problem is a problem in traffic flow theory. Given is a homogeneous freeway and the vehicle counts at two detector stations. We seek the vehicle counts at some intermediate location. The method can be applied to incident detection and diagnosis by comparing the observed and predicted data, so a realistic solution to this problem is important. Newell G.F. proposed a simple method to solve this problem. In Newell's method, one gets the cumulative count curve (N-curve) of any intermediate location just by shifting the N-curves of the upstream and downstream detectors. Newell's method was developed before the variational theory of traffic flow was proposed to deal systematically with vehicle counts. This article shows how Newell's method fits in the context of variational theory. A special case to demonstrate Newell's method Assumption. In this special case, we use the Triangular Fundamental Diagram (TFD) with three parameters: free flow speed v_f, wave velocity -w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fundamental Diagram Of Traffic Flow
The fundamental diagram of traffic flow is a diagram that gives a relation between road traffic flux (vehicles/hour) and the traffic density (vehicles/km). A macroscopic traffic model involving traffic flux, traffic density and velocity forms the basis of the fundamental diagram. It can be used to predict the capability of a road system, or its behaviour when applying inflow regulation or speed limits. Basic statements * There is a connection between traffic density and vehicle velocity: The more vehicles are on a road, the slower their velocity will be. * To prevent congestion and to keep traffic flow stable, the number of vehicles entering the control zone has to be smaller or equal to the number of vehicles leaving the zone in the same time. * At a critical traffic density and a corresponding critical velocity the state of flow will change from stable to unstable. * If one of the vehicles brakes in unstable flow regime the flow will collapse. The primary tool for graphically ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microscopic Traffic Flow Model
Microscopic traffic flow models are a class of scientific models of vehicular traffic dynamics. In contrast, to macroscopic models, microscopic traffic flow models simulate single vehicle-driver units, so the dynamic variables of the models represent microscopic properties like the position and velocity of single vehicles. Car-following models Also known as ''time-continuous models'', all car-following models have in common that they are defined by ordinary differential equations describing the complete dynamics of the vehicles' positions x_\alpha and velocities v_\alpha. It is assumed that the input stimuli of the drivers are restricted to their own velocity v_\alpha, the net distance (bumper-to-bumper distance) s_\alpha = x_ - x_\alpha - \ell_ to the leading vehicle \alpha-1 (where \ell_ denotes the vehicle length), and the velocity v_ of the leading vehicle. The equation of motion of each vehicle is characterized by an acceleration function that depends on those input stimuli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microsimulation
Microsimulation (from microanalytic simulation or microscopic simulation) is a category of computerized analytical tools that perform highly detailed analysis of activities such as highway traffic flowing through an intersection, financial transactions, or pathogens spreading disease through a population. Microsimulation is often used to evaluate the effects of proposed interventions before they are implemented in the real world. For example, a traffic microsimulation model could be used to evaluate the effectiveness of lengthening a turn lane at an intersection, and thus help decide whether it is worth spending money on actually lengthening the lane. Introduction Microsimulation can be distinguished from other types of computer modeling in looking at the interaction of individual ''units'' such as people or vehicles. Each unit is treated as an autonomous entity and the interaction of the units is allowed vary depending on stochastic (randomized) parameters. These parameters are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Newell's Car Following Model
In traffic flow theory, Newell’s car-following model is a method used to determine how vehicles follow one another on a roadway. The main idea of this model is that a vehicle will maintain a minimum space and time gap between it and the vehicle that precedes it. Thus, under congested conditions, if the leading car changes its speed, the following vehicle will also change speed at a point in time-space along the traffic wave speed, ''-w''.Newell G.F. (2002) A simplified car-following theory: a lower order model. Institute of Transportation Studies, University of California, Berkeley. Overview Assuming the fundamental diagram (flow-density) is a triangular function, a traffic state ''A'' with speed ''vA'' and density ''kA'' can be assumed in the congestion region. The density on the roadway can be determined using the spacing between vehicles and is computed simply the equation: ''kA = 1/sA'' Geometric relations from the fundamental diagram can be used to calculate the density ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Road Traffic Control
: ''For the road traffic science, see various articles under Road traffic management.'' Road traffic control involves directing vehicular and pedestrian traffic around a construction zone, accident or other road disruption, thus ensuring the safety of emergency response teams, construction workers and the general public. Traffic control also includes the use of CCTV and other means of monitoring traffic by local or state roadways authorities to manage traffic flows and providing advice concerning traffic congestion. Traffic Control Technicians (TCT's) or Traffic Control Supervisors (TCS's) are often known as "lollipop men" (usually this name only applies to TCT's working near schools to aid pupils in road crossing) from the appearance of their ''Stop/Slow'' signs, known as "Stop bats". Overview Road Traffic control is an outdoors occupation, night or day for long hours in all weathers, and is considered a dangerous occupation due to the high risk of being struck by passing vehi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rule 184
Rule 184 is a one-dimensional binary cellular automaton rule, notable for solving the majority problem as well as for its ability to simultaneously describe several, seemingly quite different, particle systems: * Rule 184 can be used as a simple model for traffic flow in a single lane of a highway, and forms the basis for many cellular automaton models of traffic flow with greater sophistication. In this model, particles (representing vehicles) move in a single direction, stopping and starting depending on the cars in front of them. The number of particles remains unchanged throughout the simulation. Because of this application, Rule 184 is sometimes called the "traffic rule". * Rule 184 also models a form of deposition of particles onto an irregular surface, in which each local minimum of the surface is filled with a particle in each step. At each step of the simulation, the number of particles increases. Once placed, a particle never moves. * Rule 184 can be understood in term ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Traffic Bottleneck
A traffic bottleneck is a localized disruption of vehicular traffic on a street, road, or highway. As opposed to a traffic jam, a bottleneck is a result of a specific physical condition, often the design of the road, badly timed traffic lights, or sharp curves. They can also be caused by temporary situations, such as vehicular accidents. Bottlenecks can also occur in other methods of transportation. Capacity bottlenecks are the most vulnerable points in a network and are very often the subject of offensive or defensive military actions. Capacity bottlenecks of strategic importance - such as the Panama Canal where traffic is limited by the infrastructure - are normally referred to as choke points; capacity bottlenecks of tactical value are referred to as mobility corridors. Causes Traffic bottlenecks are caused by a wide variety of things: * Construction zones where one or more existing lanes become unavailable (as depicted in the diagram on the right) * Accident sites that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Traffic Counter
A traffic count is a count of vehicular or pedestrian traffic, which is conducted along a particular road, path, or intersection. A traffic count is commonly undertaken either automatically (with the installation of a temporary or permanent electronic traffic recording device), or manually by observers who visually count and record traffic on a hand-held electronic device or tally sheet. Traffic counts can be used by local councils to identify which routes are used most, and to either improve that road or provide an alternative if there is an excessive amount of traffic. Also, some geography fieldwork involves a traffic count. Traffic counts provide the source data used to calculate the Annual Average Daily Traffic (AADT), which is the common indicator used to represent traffic volume. Traffic counts are useful for comparing two or more roads, and can also be used alongside other methods to find out where the central business district ( CBD) of a settlement is located. Traffic c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Traffic Flow
In mathematics and 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. History Attempts to produce a mathematical theory of traffic flow date back to the 1920s, when Frank Knight first produced an analysis of traffic equilibrium, which was refined into Wardrop's first and second principles of equilibrium in 1952. Nonetheless, even with the advent of significant computer processing power, to date there has been no satisfactory general theory that can be consistently applied to real flow conditions. Current traffic models use a mixture of empirical and theoretical techniques. These models are then developed into traffic forecasts, and take account of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Traffic Wave
Traffic waves, also called stop waves, ghost jams, traffic snakes or traffic shocks, are traveling disturbances in the distribution of cars on a highway. Traffic waves travel backwards relative to the cars themselves. Relative to a fixed spot on the road the wave can move with, or against the traffic, or even be stationary (when the wave moves away from the traffic with exactly the same speed as the traffic). Traffic waves are a type of traffic jam. A deeper understanding of traffic waves is a goal of the physical study of traffic flow, in which traffic itself can often be seen using techniques similar to those used in fluid dynamics. It is related to the accordion effect. Mitigation It has been saidTraffic Wave Experiments William J. Beaty, 1998 that by knowing how traffic waves are created, drivers can sometimes reduce their effects ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Road Transport
Road transport or road transportation is a type of transport using roads. Transport on roads can be roughly grouped into the transportation of goods and transportation of people. In many countries licensing requirements and safety regulations ensure a separation of the two industries. Movement along roads may be by bike, automobile, bus, truck, or by animal such as horse or oxen. Standard networks of roads were adopted by Romans, Persians, Aztec, and other early empires, and may be regarded as a feature of empires. Cargo may be transported by trucking companies, while passengers may be transported via mass transit. Commonly defined features of modern roads include defined lanes and signage. Various classes of road exist, from two-lane local roads with at-grade intersections to controlled-access highways with all cross traffic grade-separated. The nature of road transportation of goods depends on, apart from the degree of development of the local infrastructure, the dis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Road Traffic Management
: ''For the road traffic science, see various articles under Road traffic management.'' Road traffic control involves directing vehicular and pedestrian traffic around a construction zone, accident or other road disruption, thus ensuring the safety of emergency response teams, construction workers and the general public. Traffic control also includes the use of CCTV and other means of monitoring traffic by local or state roadways authorities to manage traffic flows and providing advice concerning traffic congestion. Traffic Control Technicians (TCT's) or Traffic Control Supervisors (TCS's) are often known as "lollipop men" (usually this name only applies to TCT's working near schools to aid pupils in road crossing) from the appearance of their ''Stop/Slow'' signs, known as "Stop bats". Overview Road Traffic control is an outdoors occupation, night or day for long hours in all weathers, and is considered a dangerous occupation due to the high risk of being struck by passing vehic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
