Closure to “High Density Vehicular Flow-Density Relationship”

1968 ◽  
Vol 94 (2) ◽  
pp. 269-270
Author(s):  
Danilo M. Garcia ◽  
John Hugh Jones
Keyword(s):  
High Density ◽  
Flow Density ◽  
Density Relationship

scholarly journals Urban Wasteful Transport and Its Estimation Methods

2018 ◽  
Vol 10 (12) ◽  
pp. 4562 ◽  
Author(s):  
Xiangyang Cao ◽  
Bingzhong Zhou ◽  
Qiang Tang ◽  
Jiaqi Li ◽  
Donghui Shi
Keyword(s):  
Traffic Flow ◽  
Traffic Congestion ◽  
Transport Theory ◽  
Road Traffic ◽  
Urban Traffic ◽  
Flow Density ◽  
Urban Road ◽  
Road Capacity ◽  
Density Relationship

The paper studies urban road traffic problems from the perspective of resource science. The resource composition of urban road traffic system is analysed, and the road network is proved as a scarce resource in the system resource combination. According to the role of scarce resources, the decisive role of road capacity in urban traffic is inferred. Then the new academic viewpoint of “wasteful transport” was proposed. Through in-depth research, the paper defines the definition of wasteful transport and expounds its connotation. Through the flow-density relationship analysis of urban road traffic survey data, it is found that there is a clear boundary between normal and wasteful transport in urban traffic flow. On the basis of constructing the flow-density relationship model of road traffic, combined with investigation and analysis, the quantitative estimation method of wasteful transport is established. An empirical study on the traffic conditions of the Guoding section of Shanghai shows that there is wasteful transport and confirms the correctness of the wasteful transport theory and method. The research of urban wasteful transport also reveals that: (1) urban road traffic is not always effective; (2) traffic flow exceeding road capacity is wasteful transport, and traffic demand beyond the capacity of road capacity is an unreasonable demand for customers; (3) the explanation that the traffic congestion should apply the comprehensive theory of traffic engineering and resource economics; and (4) the wasteful transport theory and method may be one of the methods that can be applied to alleviate traffic congestion.

scholarly journals Travel Time and Congestion Assessment Along Ujala Circle (S.G. Highway Ahmedabad)

2020 ◽  
Vol 9 (5) ◽  
pp. 995-1004
Keyword(s):  
Travel Time ◽  
Traffic Congestion ◽  
Calculated Data ◽  
Noise Pollution ◽  
Flow Density ◽  
Time Loss ◽  
Environment Effects ◽  
Speed Flow ◽  
Density Relationship ◽  
Data Graph

The approximately 25201084 (2018) vehicular citizenry in Ahmedabad city so it is very necessary to negotiate its movements and infirmity effects like as air and noise pollution & other environment effects, traffic congestion, time loss, and so on. S.G Highway has 44.5 km long stretch of Ahmedabad, an oldest and most substantial stretch which started from Ujala circle. For declamation the traffic congestion, classified volume count survey (by Video Graphic method), travel time and delay survey (by Moving Observer Method), and for speed-flow-density relationship Spot speed study at Ujala circle during Friday has been accomplished and analyzed. From the calculated data, graph of flow v/s density, speed v/s density and speed v/s flow relationship has been prosecute with the R2 value of each relationship. This analysis proved that current traffic situation at Ujala circle is highly congested, which leads to the higher travel time taken by vehicle compare to free flow condition. From all analyzed data, alternate invigorating measures are prospected. Based on those alternative invigorating measures best alternative is choose as well as bring off simulation and validation of Model in the VISSIM software, also design in AutoCAD for better illustration of issue.

Calibration of Flow–Density Relationships on Urban Streets

2005 ◽  
Vol 1934 (1) ◽  
pp. 226-234 ◽  
Author(s):  
Ludovic Leclercq
Keyword(s):  
Urban Areas ◽  
Flow Density ◽  
Traffic Data ◽  
Urban Streets ◽  
Traffic State ◽  
Calibration Methods ◽  
Density Relationship ◽  
Traffic Behavior ◽  
Best Fit ◽  
Selection Of

The aim of this paper is to gather some observations resulting from the study of traffic data in an urban environment (Toulouse, France) rather than on freeways, as is often the case in papers that deal with flow–density relationship calibration. Methods developed for freeway data are studied and new ones are presented to address the specificity of traffic behavior in urban areas. A two-step approach is proposed. First, the data are processed to obtain consistent observations for simulation use. This processing includes the calculation of density from occupancy and space mean speed and the aggregation and the selection of data to make them suitable for equilibrium traffic state representation. Then, a best-fit curve is applied to the selected data to obtain flow–density relationships. Finally, the resulting relationships are studied to highlight the peculiarities of traffic behavior in urban streets.

scholarly journals Expansion of the Fundamental Diagram from a Microscopic Multilane Modeling Framework of Mixed Traffic

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Mudasser Seraj ◽  
Jiangchen Li ◽  
Tony Z. Qiu
Keyword(s):  
Accurate Estimation ◽  
Flow Density ◽  
Mixed Traffic ◽  
Gap Acceptance ◽  
Fundamental Diagram ◽  
Lane Changing ◽  
Car Following ◽  
Proposed Model ◽  
Density Relationship ◽  
Motion Dynamics

Microscopic modeling of mixed traffic (i.e., automaton-driven vehicles and human-driven vehicles) dynamics, particularly car-following, lane-changing, and gap-acceptance, provides the opportunity to gain a more accurate estimation of flow-density relationships for both traditional traffic with human-driven vehicles and different mixed traffic scenarios. Our paper proposes a microscopic framework to model multilane traffic for both vehicle types on shared roadways which sets the stage to explore the capability of macroscopic car-following models in general to explain the fundamental flow-density relationship. Since prior models inadequately represent the fundamental diagram realistically, we propose a rectified macroscopic flow model that can account for the impact of both lane-changing and gap-acceptance. Differentiability, boundary conditions, and flexibility of the proposed model are tested to validate its applicability. Finally, the capability to interpret the flow-density relationship by the proposed model is verified for different mixed traffic scenarios. Although few model parameter values were obtained directly from the simulation input, the rest of the parameters have been calibrated by flow and density outputs from the simulations. The analysis results show a distinct correlation between the proposed model parameters with automation-driven vehicle shares and lane-changing rates of traffic. The findings from this study emphasize the importance of taking complete motion dynamics into account, rather than partial motion dynamics (i.e., car-following) as has been the case in the previous studies, to explain macroscopic traffic flow characteristics, irrespective of the vehicle type.

Discussion of “High Density Vehicular Flow-Density Relationships”

1966 ◽  
Vol 92 (2) ◽  
pp. 112-117
Author(s):  
John J. Haynes ◽  
Adolf D. May ◽  
Joseph L. Schofer
Keyword(s):  
High Density ◽  
Flow Density

Impact of Stochasticity on Traffic Flow Dynamics in Macroscopic Continuum Models

2020 ◽  
Vol 2674 (10) ◽  
pp. 690-704
Author(s):  
Shi-Teng Zheng ◽  
Rui Jiang ◽  
Bin Jia ◽  
Junfang Tian ◽  
Ziyou Gao
Keyword(s):  
Traffic Flow ◽  
Second Order ◽  
Flow Density ◽  
Stochastic Flow ◽  
Order Model ◽  
Macroscopic Models ◽  
Density Relationship ◽  
Growth Feature ◽  
The Impact ◽  
Second Order Model

Stochasticity is an indispensable factor for describing real traffic situations. Recent experimental study has shown that a model spanning a two-dimensional speed–spacing (or speed–density) relationship has the potential to reproduce the characteristics of traffic flow in both experiments and empirical observations. This paper studies the impact of stochasticity on traffic flow in macroscopic models utilizing the stochastic flow–density relationship. Numerical analysis is conducted under the periodic boundary to study the impact of stochasticity on stability. Traffic flow upstream of a bottleneck is also investigated to study the impact of stochasticity on the oscillation growth feature. It is shown that there is only a quantitative difference for model stability after introducing stochasticity. In contrast, a qualitative change of the traffic oscillation growth feature can be clearly observed. With the introduction of stochasticity, traffic oscillations begin to grow in a concave way along the road. Sensitivity analysis is also performed. It is found that, under the stochastic flow–density relationship: (i) with the decrease of relaxation time, the second-order model becomes stable; (ii) the smaller the propagation speed of small disturbance, the much stronger the traffic oscillation; (iii) the larger the fluctuation range, the sooner the traffic oscillation fully develops; and (iv) the changing probability has trivial impact on the simulation results. Finally, model calibration and validation are conducted. It is shown that the experimental spatiotemporal patterns can be captured by macroscopic models under the stochastic flow–density relationship, especially the second-order model.

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