scholarly journals Developing a New Spatial Unit for Macroscopic Safety Evaluation Based on Traffic Density Homogeneity

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Chen Wang ◽  
Lin Liu ◽  
Chengcheng Xu
Keyword(s):  
Traffic Flow ◽  
Traffic Control ◽  
Flow Characteristics ◽  
Traffic Density ◽  
Minimization Method ◽  
Spatial Unit ◽  
Flow Parameters ◽  
Safety Knowledge ◽  
Traffic Operation ◽  
Crash Modeling

Macrolevel crash modeling has been extensively applied to investigate the safety effects of demographic, socioeconomic, and land use factors, in order to add safety knowledge into traffic planning and policy-making. In recent years, with the increasing attention to regional traffic management and control, the safety effects of macrolevel traffic flow parameters may also be of interest, in order to provide useful safety knowledge for regional traffic operation. In this paper, a new spatial unit was developed using a recursive half-cut partitioning procedure based on a normalized cut (NC) minimization method and traffic density homogeneity. Two Bayesian lognormal models with different conditional autoregressive (CAR) priors were applied to examine the safety effects of traffic flow characteristics at the NC level. It was found that safety effects of traffic flow exist at such macrolevel, indicating the necessity of considering safety for regional traffic control and management. Furthermore, traffic flow effects were also examined for another two spatial units: Traffic Analysis Zone (TAZ) and Census Tract (CT). It was found that ecological fallacy and atomic fallacy could exist without considering traffic flow parameters at those planning-based levels. In general, safety needs to be considered for regional traffic operation and the effects of traffic flow need to be considered for spatial crash modeling at various spatial levels.

scholarly journals On the safety effects of spatially aggregated traffic flow parameters at macro-levels

2019 ◽  
Vol 11 (1) ◽  
pp. 168781401881940
Author(s):  
Chen Wang ◽  
Lin Liu ◽  
Zhenbo Lu
Keyword(s):  
Traffic Flow ◽  
Management Strategies ◽  
Central Area ◽  
Model Performance ◽  
Graph Cut ◽  
Crash Risk ◽  
Traffic Density ◽  
Minimization Method ◽  
Flow Parameters ◽  
Regional Management

Traffic flow parameters have been found to significantly affect crash risk at micro-levels. If such effects do exist at macro-levels, at least two benefits could be expected: (1) the performance and estimates of planning-based crash models could be improved and (2) useful safety knowledge could be provided for regional traffic management. In this article, a flow-based spatial unit was developed by a graph-cut minimization method, based on which regional management strategies are often applied. The graph-cut method partitioned the central area of Kunshan, China, into multiple sub-regions (i.e. graph-cut unit), considering traffic density homogeneity. Bayesian Poisson lognormal models with conditional autoregressive priors were utilized to examine the safety effects of traffic flow parameters, based on the traditional planning-based units and the flow-based graph-cut units. According to the results, no significant traffic flow effect was found for the traffic analysis zone–based model. Traffic flow parameters resulted in a decreased model performance and potential endogeneity issues for the census tract–based model. However, traffic flow effects were found significant for the graph-cut-based model, with an improved model performance. In general, the safety effects of macro-level traffic flow need to be considered for flow-based units developed for regional management.

Modeling Multiple User-Class Traffic

1998 ◽  
Vol 1644 (1) ◽  
pp. 57-69 ◽  
Author(s):  
Serge P. Hoogendoorn ◽  
Piet H. L. Bovy
Keyword(s):  
Traffic Flow ◽  
Traffic Control ◽  
Flow Characteristics ◽  
Traffic Density ◽  
Class Model ◽  
Specific Flow ◽  
Flow Models ◽  
Multiple User ◽  
Equilibrium Relationships ◽  
Traffic Composition

In contemporary traffic flow theory, the distinction between user classes is rarely made. However, we envisage that the accuracy and the descriptive power of the macroscopic traffic flow models can be improved significantly by separating user classes and their specific flow characteristics. As a consequence, the possibility of improved estimation and prediction of traffic flow conditions becomes available. Additionally, the availability of a realistic multiple user-class traffic flow model enables the automated generation of user-dedicated traffic control policies by means of mathematical optimal control theory. A macroscopic multiple user-class model is derived from mesoscopic principles. In opposition to earlier multiple user-class models, the model presented here implicitly defines equilibrium relationships between traffic density and equilibrium velocities as a function of current traffic conditions, traffic composition, and distribution of user-class-dependent desired velocities. Additionally, the velocity variance variable is introduced describing deviations from the average speed within the user classes. The multiple user-class model identifies competing processes. On the one hand, drivers attempt to traverse the freeway at their desired velocity; on the other hand, they adjust their velocity because of interaction with slower vehicles. These processes can result in self-formation of apparently random local structures. Finally, the proposed model satisfies the anisotropy condition and the invariant personality condition.

scholarly journals Macroscopic Traffic Flow Control Via State Estimation

2015 ◽  
Vol 15 (5) ◽  
pp. 5-16
Author(s):  
H. Abouaïssa ◽  
H. Majid
Keyword(s):  
Flow Control ◽  
State Estimation ◽  
Traffic Flow ◽  
Traffic Control ◽  
Traffic Density ◽  
Traffic State ◽  
Loop Detectors ◽  
Traffic State Estimation ◽  
Estimation And Control ◽  
And Control

Abstract The studies presented in this paper deal with traffic control in case of missing data and/or when the loop detectors are faulty. We show that the traffic state estimation plays an important role in traffic prediction and control. Two approaches are presented for the estimation of the main traffic variables (traffic density and mean speed). The state constructors obtained are then used for traffic flow control. Several numerical simulations show very promising results for both traffic state estimation and control.

Application of Catastrophe Theory in Traffic Flow of Highway Tunnel Group

2013 ◽  
Vol 734-737 ◽  
pp. 1609-1612
Author(s):  
Wei Zhan ◽  
Yue Quan Shang ◽  
Feng Xia Chi
Keyword(s):  
Traffic Flow ◽  
Traffic Control ◽  
Catastrophe Theory ◽  
Critical Density ◽  
Flow Characteristics ◽  
Control Measures ◽  
Highway Tunnel ◽  
Relationship Of ◽  
The Relationship ◽  
Highway Management

Based on the investigation of traffic flow in a typical highway tunnel group, the traffic flow characteristics were analyzed by catastrophe theory with the relationship of the speed, volume and density. The discontinuous leaping change phenomenon of the traffic data under large traffic volume is better explained by the catastrophe model than the traditional ways. The value of critical density can be obtained by analyzing the critical state of traffic flow. Then the traffic flow warning can be realized in highway tunnel group region. The data and results can be used for the reference of taking traffic control measures by highway management.

scholarly journals Left-Side On-Ramp Metering for Improving Safety and Efficiency in Underground Expressway Systems

2019 ◽  
Vol 11 (12) ◽  
pp. 3247 ◽  
Author(s):  
Minhua Shao ◽  
Congcong Xie ◽  
Lijun Sun ◽  
Xiaomin Wan ◽  
Zhang Chen
Keyword(s):  
Traffic Flow ◽  
Traffic Safety ◽  
Traffic Control ◽  
Flow Characteristics ◽  
Ramp Metering ◽  
Accident Risk ◽  
Data Traffic ◽  
Traffic Efficiency ◽  
Traffic Characteristics ◽  
Two Parameter

As one of the effective measures of intelligent traffic control, on-ramp metering is often used to improve the traffic efficiency of expressways. Existing on-ramp metering research mainly discusses expressways with right-side on-ramps. However, for underground expressway systems (UESs), left-side on-ramps are frequently adopted to reduce the ground space occupied by ramp construction. Since traffic entering from the left and right sides of the mainline may have different traffic characteristics, on-ramp metering for UESs with left-side on-ramps should be explored specifically. This study examines the impacts of left-side on-ramps on the traffic safety and efficiency of UESs and proposes an effective on-ramp metering strategy. Firstly, using field data, traffic flow fundamental diagrams and speed dispersion are discussed to explore the traffic flow characteristics of the “left-in” UES. The results show that the capacity and critical occupancy are both reduced in left-side on-ramp compared to right-side on-ramp expressways. Meanwhile, the speed dispersion is higher in left-side on-ramp UESs, which means a higher accident risk. Based on this, considering traffic safety and efficiency, a novel two-parameter left-side on-ramp metering strategy for UESs is proposed, in which occupancy and speed are used as the control indicators simultaneously. Additionally, the mechanism of the metering strategy is explained. Finally, the proposed on-ramp metering strategy is simulated on a real UES. The results demonstrate the advantages of the proposed two-parameter on-ramp metering strategy for improving the traffic safety and efficiency of UESs.

Research on Bus Stop Based on Cellular Automaton Model

2014 ◽  
Vol 1008-1009 ◽  
pp. 1484-1488
Author(s):  
Jun Qian ◽  
Yong Ju Hu
Keyword(s):  
Cellular Automaton ◽  
Traffic Flow ◽  
Simulation Analysis ◽  
Flow Characteristics ◽  
Negative Influence ◽  
Traffic Density ◽  
Matlab Simulation ◽  
Bus Stop ◽  
Local Roads ◽  
The Relationship

Based on the NaSch model,a cellular automaton mode with two lanes is proposed by computer simulation analysis,which considers the influence of passengers on bus stop.By using MatLab simulation,the paper compares the different traffic flow characteristics between harbor-shaped and nonharbor shaped bus stop.It also analyzes the relationship between the traffic flow and the number of bus,the scope and intensity of bus stop in different ways.The results show that harbor-shaped bus stop is the effective method to alleviate the crowd traffic in the case of larger traffic density;It takes more passengers in the system which used harbor shaped bus stop can accommodate more buses;Harbor-shaped bus stop produced better improvement in the negative influence of bus stopping on local roads.

Study on Vehicle’s Arrival Rule and Relation between Traffic Flow Parameters on Snowy Pavement

2012 ◽  
Vol 446-449 ◽  
pp. 2528-2531
Author(s):  
Li Xin Wu ◽  
Guo Zhu Cheng
Keyword(s):  
Traffic Flow ◽  
Flow Characteristics ◽  
Traffic Volume ◽  
Flow Parameters ◽  
Traffic Flow Characteristics ◽  
Binominal Distribution

There are great difference in traffic flow characteristics between snowy pavement and non-snowy pavement. Ten road sections were investigated and the data of traffic volume, headway, speed and density on snowy and non-snowy pavement were collected. Vehicle’s arrival rules were compared and reasonable distribution was given. The relation between traffic volume and speed, density and traffic volume were compared between snowy pavement and non-snowy pavement. It indicated that negative binominal distribution is more fit to vehicle’s arrival frequency on snowy pavement. Speed decreases for the same traffic volume and traffic volume decreases for the same density on snowy pavement.

scholarly journals Adaptive Traffic Management System using CNN (YOLO)

2021 ◽  
Vol 9 (VI) ◽  
pp. 3726-3732
Author(s):  
B. Sowmya
Keyword(s):  
Real Time ◽  
Traffic Flow ◽  
Traffic Control ◽  
Traffic Congestion ◽  
Traffic Management ◽  
Object Identification ◽  
Traffic Signal ◽  
Traffic Density ◽  
Loop Control ◽  
Control Framework

The huge number of vehicles on the roadways is making congestion a significant problem. The line longitudinal vehicle waiting to be processed at the crossroads increases quickly, and the traditionally used traffic signals are not able to program it properly. Manual traffic monitoring may be an onerous job since a number of cameras are deployed over the network in traffic management centers. The proactive decision-making of human operators, which would decrease the effect of events and recurring road congestion, might contribute to the easing of the strain of automation.The traffic control frameworks in India are now needed as it is an open-loop control framework, without any input or detection mechanism. Inductive loops and sensors employed in existing technology used to detect the number of passing vehicles. The way traffic lights are adapted is highly inefficient and costly in this existing technology. The aim was to build a traffic control framework by introducing a system for detection ,which gives an input to the existing system (closed loop control system) in order to adapt to the changing traffic density patterns and to provide the controller with a crucial indication for ongoing activities. By this technique, the improvement of the signals on street is extended and thus saves time by preventing traffic congestion. This study proposes an algorithm for real-time traffic signal control, depending on the traffic flow. In reality, the features of competitive traffic flow at the signposted road crossing are used by computer vision and by machine learning. This is done by the latest, real-time object identification, based on convolutional Neural Networks network called You Look Once (YOLO). Traffic signal phases are then improved by data acquired in order to allow more vehicles to pass safely over minimal wait times, particularly the line long and the time of waiting per vehicle.This adjustable traffic signal timer is used to calculate traffic density utilizing YOLO object identification using live pictures of cameras in intervals and adjusts the signal timers appropriately, therefore decreasing the road traffic congestion, ensuring speedier transit for persons, and reducing fuel consumption. The traffic conditions will improve enormously at a relatively modest cost. Inductive loops are a viable but costly approach. This method thereby cuts expenses and outcomes quickly.

Study on Ice-Snow Road and its Traffic Operating Characteristics in Wintry Harbin China

2011 ◽  
Vol 97-98 ◽  
pp. 587-590
Author(s):  
Li Wei Hu ◽  
Yu Long Pei
Keyword(s):  
Traffic Flow ◽  
Flow Characteristics ◽  
Operating Characteristics ◽  
Urban Road ◽  
Traffic Delays ◽  
Flow Information ◽  
Cold Area ◽  
Snow Conditions ◽  
Operation Risk ◽  
Traffic Operation

The friction coefficient (FC) will be reduced when the roads is covered by ice-snow, and the traffic operation risk will be increased in the regions(as Harbin Heilongjiang province in China) with high latitudes, whose winter is long and cold , and those conditions led to the reduction of road capacity and the increase of traffic delays. Using the video detection device, one of the traffic flow information collecting devices, a large number of data in the period of ice-snow of cold area are collected, which is the research base of this paper. The macro and micro traffic flow characteristic of urban road under ice-snow conditions is analyzed, such as the traffic flow, the distribution of headway time, and the properties of the speed distribution. The relation models of FC of ice-snow road and speed-volume are built. Then, the traffic flow characteristics are compared between ice-snow and non- ice-snow road. The outcomes studied above are the foundation for analyzing traffic operation and capacity of urban road in the period of ice-snow.

scholarly journals Characteristics of traffic flows at roundabouts in the city of Banja Luka before and during COVID-19 crisis

2021 ◽  
Vol 67 (4) ◽  
pp. 31-35
Author(s):  
Nemanja Garunovic ◽  
Vuk Bogdanović ◽  
Slavko Davidović ◽  
Valentina Mirović ◽  
Jelena Mitrović Simić
Keyword(s):  
Traffic Flow ◽  
Flow Characteristics ◽  
Traffic Condition ◽  
State Of Emergency ◽  
Flow Parameters ◽  
Pedestrian Traffic ◽  
The Difference ◽  
Banja Luka ◽  
Restrictive Measures ◽  
The City

COVID-19 pandemic caused many restrictive measures. Most of these measures were in the relationship with the restrictions of mobility which caused some differences in traffic flow demands. In this paper the comparative analysis of traffic flow characteristics at roundabouts in the City of Banja Luka was conducted. The analysis included two different states of traffic condition: the first one, normal condition before COVID-19 crisis, and the second one, during the state of emergency caused by the pandemic. The analysis shows the difference between some of motorized vehicle and pedestrian traffic flow parameters.

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