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In the study of traffic flow theory, the flow-density diagram is used to determine the traffic state of a roadway. Currently, there are two types of flow density graphs: parabolic and triangular. Academia views the triangular flow-density curve as more the accurate representation of real world events. The triangular curve consists of two vectors.
In traffic flow, the two most important densities are the critical density (k c) and jam density (k j). The maximum density achievable under free flow is k c , while k j is the maximum density achieved under congestion.
The movement of the downstream jam front can be illustrated in the flow-density plane by a line, which is called "Line J" (Line J in Figure 8). The slope of Line J is the velocity of the downstream jam front . Figure 8: Three traffic phases on the flow-density plane in Kerner’s three-phase traffic theory
Assuming the fundamental diagram (flow-density) is a triangular function, a traffic state A with speed v A and density k A 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: k A = 1/s A
A macroscopic traffic flow model is a mathematical traffic model that formulates the relationships among traffic flow characteristics like density, flow, mean speed of a traffic stream, etc. Such models are conventionally arrived at by integrating microscopic traffic flow models and converting the single-entity level characteristics to ...
Additionally, beyond a further threshold, increased density reduces flow as well. Therefore, speeds and lane flows at bottlenecks can be kept high during peak periods by managing traffic density using devices that limit the rate at which vehicles can enter the highway.
Level of service (LOS) is a qualitative measure used to relate the quality of motor vehicle traffic service. LOS is used to analyze roadways and intersections by categorizing traffic flow and assigning quality levels of traffic based on performance measure like vehicle speed, density, congestion, etc.
Historical and recent information of a traffic network about its density and flow, a model of the transport network infrastructure and algorithms referring to both spatial and temporal dimensions. The final objective is to provide a better optimization of the traffic infrastructure such as traffic lights.