Methodology for simulating heterogeneous traffic on expressways in developing countries: a case study in India

In this paper, the characteristics of traffic flow on urban expressway in Beijing are investigated. Based on the real data, some classical traffic flow models are used to explore the relationships among traffic flow, speed and time occupancy. The FCM (fuzzy C-means method) clustering algorithm is applied to classify the traffic flow state. The results show that the Greenshields model is the best suitable model for the mathematical description of traffic flow, i.e. traffic speed and time occupancy is in linear relation while traffic volume and time occupancy (traffic speed) is in parabolic relation. Four different traffic flow states, including free flow, steady flow, synchronized flow and congested flow, are identified according to the FCM clustering method. For the free traffic flow, the time occupancy cluster center is equal to 0.16, and the traffic volume cluster center is equal to 980 pcu/h. For the steady traffic flow, the time occupancy cluster center is equal to 0.30, and the traffic volume cluster center is equal to 1737 pcu/h. For the synchronized traffic flow, the time occupancy cluster center is equal to 0.50, and the traffic volume cluster center is equal to 1896 pcu/h. For the congested traffic flow, the time occupancy cluster center is equal to 0.79, and the traffic volume cluster center is equal to 1184 pcu/h. The analysis of traffic flow characteristics in this study can provide the method and data foundation to evaluate the traffic service level and enhance the traffic organization and management.

This paper studies the risk assessment of traffic flow on major highways under high-speed driving conditions and the safety warning after traffic incidents. Firstly, by analyzing the operation characteristics of the main line traffic flow and the evolution characteristics of the upstream traffic flow after the event, a collaborative control strategy for the dynamic assessment and accurate early warning of the main line traffic flow is proposed. Secondly, based on the operating speed, traffic flow and head-time distance state parameters of the main traffic flow, the risk assessment model of the main traffic flow is established, which provides an algorithm basis for the safe operation status evaluation and active control of the main traffic flow. Third, based on the driver’s reaction process after the traffic incident and the evolution process of main traffic flow, a traffic incident safety warning distance function is proposed, which provides a quantitative function for the accurate early warning and prevention of traffic accidents in the upstream traffic flow after traffic incidents. Through the dynamic assessment and control of operation risks of expressway main line traffic flow, the accurate risk warning of expressway main line traffic flow under the traffic event conditions will significantly improve the dynamic safety control level and risk warning ability of the expressway main line.

Bifurcation analysis and control of macro traffic flow models based on real-time traffic state influence

This paper proposes a new clustering algorithm for global positioning system (GPS)-based mobile ad hoc networks that takes into consideration the direction of the overall traffic flow in the network. The proposed cluster leader logic algorithm is motivated by the GPS quorum hybrid routing algorithm, where clusterheads are positioned on the terrain upon a conceptual cellular grid. The proposed distributed clustering algorithm chooses the clusterheads based on the traffic flow patterns, i.e. the nodes best suited to forward and route network traffic are selected. Our approach allows a clusterhead which is overwhelmed with sending packets to identify an additional clusterhead from nodes available in its cell to share its load. Likewise, clusterheads with low load will try to relinquish their role as a clusterhead. We propose a new concept called cell fanning that allows collocated clusterheads in one cell to share routing responsibilities by declaring which cells they are responsible for routing packets to. We conducted extensive simulation experiments with enforced directional traffic patterns. Two important results are presented: power consumption per clusterhead and average queuing delay for each clusterhead. Results in terms of message overheads, number of clusterheads, power consumption, and queuing delay reveal that system performance is enhanced when clusterheads are chosen considering the direction of the traffic flow.

Lagrangian generic second order traffic flow models for node

Introduction. Problematic sections of the road network are intersections with high traffic intensity of conflicting pedestrian and traffic flow, in particular, right and left turns. At such crossings, there are significant traffic delays. In the case of vehicles turning left or right at an intersection when passing at a traffic light signal that allows traffic, should give way to pedestrians crossing the roadway on the crosswalk. In the case of high intensity of pedestrian traffic, it is impossible to complete the turn of such vehicles, they remain at the intersection, so there are significant traffic delays for returning vehicles.Purpose. Therefore, the work aims to study the interaction of traffic and pedestrian flows with high intensity at regulated intersections to improve their capacity.Methods. To study the parameters of traffic flows, in particular, the length of congestion, we used traffic flow models, which include a psychophysiological model of following a vehicle moving in front, and a model based on traffic rules. To model, pedestrian flows the Wiedemann model was used. The leastsquares method was used to obtain empirical nonlinear dependences of congestion length on the intensities of conflicting pedestrian and traffic flows.Results. The paper uses known methods for solving applied problems in the field of traffic for some unique cases, namely the intersection of intensive -traffic and pedestrian flows. Studies of road and pedestrian traffic parameters at crossings have shown that the length of congestion significantly depends on the intensity of traffic flow, but with increas-ing intensity of pedestrian traffic more than 1000 people/h, the length of congestion changes insignificantly. If there are trams at the intersection, the length of congestion increases by an average of 1.14% and depends significantly on the intensity of traffic and pedestrian flows.It is proposed to introduce three-phase traffic light regulation on such sections when one of the phases allows traffic only for pedestrians. The simulation results showed that the length of congestion in the absence of rail vehicles on the approaches to the intersection decreases by an average of 45.3% and is weakly dependent on the intensity of pedestrian flows. If there are rail vehicles at the crossing, the length of congestion can reduce by an average of 13.7%. But in some cases may increase.Conclusion. The research methodology presented in this paper can be used for intersections with another traffic organization scheme to justify the feasibility of introducing threephase traffic light control when one of the phases allows traffic only to pedestrians.

In order to study the quantitative influence of driver's behavior on road traffic, the cellular automaton dynamic model with influences on drivers (IDCA) is proposed based on the NaSch model in this paper for the characteristics of the driver's behavior. The improved model combines field force and graph theory to simulate road traffic flow. According to the driver's behavior characteristics, these factors are considered in the model, such as the direct physical and indirect psychological effects on driver, relative speed and vehicle characteristic. The influences of driver types and vehicle flow evolution mechanism on traffic flow are studied based on the model through computer numerical simulation. The simulation results show that the IDCA model can simulate abundant traffic behaviors better than the NaSch model, which reappears synchronous flow and other complex traffic phenomena. Traffic flows have better stability and higher dissolving congestion efficiency in the IDCA model through the analysis of the fluctuation of vehicles' speed and the vehicles' headway-distance. In addition, by using the computer numerical simulation of the IDCA model, the density-velocity and density-flow diagrams of the mixed traffic flow composed of different driver types are obtained. The conclusions are obtained: the larger the proportion of aggressive drivers, the larger the vehicle speed and traffic flow under the same road medium density and high density, and traffic flow decreases with the increase of the proportion of conservative drivers. The phenomenon of high speed car-following is simulated at last. The result of the rate of high speed car-following in the small headway areas more than 7% is obtained, which is consistent with the measured results.

Traffic Modeling and Safety Analysis on Motorway Ramps

The vehicles normally move at their free speeds when it is least impeded due to traffic flow under lean traffic (free flow) conditions. As traffic flow increases, the vehicles cannot sustain their free speeds due to interactions from other vehicles in the traffic stream. In addition to that the vehicles that are operating in the congested traffic conditions will consume more fuel than those operating in steady state traffic conditions for the same average speed. This leads to increase in travel time and fuel consumption of the vehicles and thereby adding to total road user cost (RUC). On the contrary, fuel consumption is also high at very high speeds under free flow traffic flow conditions leading to increase RUC. Considering these scenarios, the travel time and fuel cost of the vehicle due to the congestion and free flow conditions (uncongested) has to be necessarily modelled in order to estimate realistic assessment of RUC on Indian highways. In the present study, the congestion cost relationships have been developed between Congestion Factor, a ratio of cost under congestion and steady state conditions and Volume-Capacity Ratio by considering various vehicle types plying on varying widths of multi-lane highways (four, six and eight lane divided carriageways) through the collection of exhaustive time related and fuel related data. Time related data was collected through questionnaire survey method whereas fuel consumption data was collected using advanced sophisticated fuel flow measuring equipment (V-Box). The developed equations have been successfully applied to demonstrate their applicability in terms of estimating realistic effect of congestion on time and fuel cost by considering a section on NH-2 in Delhi. The analysis shows that the congestion effect is more significant on fuel cost for heavy commercial vehicles whereas it is more prominent on time cost for passenger vehicles. However, the congestion effect on combined fuel and time cost is more significant on multi-axle trucks followed by cars, two wheelers and buses.

The study of traffic flow characteristics is essential for designing highway systems for which different traffic influencing variables are of primary importance. The study aims to assess the impact of a range of traffic flow and density levels on the spatio-temporal (lateral placement and time headway) traffic characteristics of highways. A substantial amount of traffic data like speed, time headway (TH), and lateral placement (LP) of vehicles was collected continuously for 12 h on six Indian highway sections. The DPCU for different vehicles with different flow and density rates were calculated. The speed and TH descriptive statistics and probability distribution functions at varying flow and density levels were also analyzed. To determine the most appropriate probability distribution function, the goodness of fit test was used. Furthermore, the impact of traffic speed, flow, and density on the LP of vehicles under different traffic conditions was assessed using descriptive statistics. It was observed that the traffic flow and density levels had an unusual effect on the DPCUs of vehicles. The mean traffic speed under high flow and density decreased by 33.3 and 18.3%, while the mean TH under high flow and density decreased by 28.4 and 29.9%. Also, the results indicated that traffic speed and TH data exhibit a different distribution of probability functions depending on the traffic flow and density. The descriptive statistics on the LP of vehicles show the existence of a significant difference of the same concerning the different ranges of traffic speed, flow, and density.KeywordsSpeedFlowDensityTime headwayLateral placementMixed traffic

An Analysis on Mixed Traffic Flow of Conventional Passenger Cars and Microcars Using a Cellular Automata Model

As a typical type of adverse weather, heavy rainfall can result in congestion and productivity loss in the urban transportation system, which has been a severe problem for cities and attracted much attention from scholars. However, little attention has been paid to the effects of the combination of rainfall and rain-induced waterlogging on urban road traffic. In this paper, first, an experiment based on a high-fidelity driving simulator is conducted to collect the drivers’ behavior data in the scenario of rainfall and waterlogging where 30 groups of scenarios with different levels of rainfall intensity and water depth are included. Second, different car-following models are calibrated in the light of the drivers’ behavior database from the experiment, and the best one is chosen to simulate the traffic flow on urban road sections. Lastly, different traffic flow models that depict the relationship between flow, velocity, and density are calibrated based on the simulation results. The results show that the increase of both the rainfall intensity and water depth can result in decreased free flow speed and maximum flow. The results also show that the depth of water is more critical as an influencing factor on the characteristics of traffic flow compared with the rainfall intensity. The results from this study can facilitate a deeper understanding of the influence of rainfall and waterlogging on traffic flow and improve the response capacity of traffic management departments when faced with rainfall and waterlogging.

In Southeast Asia, motorcycles constitute a substantial portion of road traffic. Thus, a passenger-car-oriented traffic control system cannot operate effectively, and traffic efficiency is decreased. To achieve a sustainable and environmentally friendly society, a traffic control system suitable for mixed traffic including motorcycles is highly necessary. Although some traffic policies targeting motorcycles have been implemented, the criteria for implementing them are still unclear. Indeed, the characteristics of motorcycle-dominant traffic flow are not well understood. Thus, this study attempts to qualify the effect of motorcycle-oriented traffic operations and find the criteria for implementing them on the basis of detailed investigations of mixed traffic flow with motorcycles in various cities with differing traffic conditions. The results show that (1) unclear definition of traffic lanes may severely decrease the efficiency of traffic flow and (2) the most effective traffic scheme varies with traffic conditions.

Modeling the asymmetry in traffic flow (b): Macroscopic approach

The state of the art of macroscopic vehicle traffic flow models is discussed and the traffic flow stability of these models is analyzed. A nonlinear traffic flow stability criterion is investigated using the wavefront expansion technique. Qualitative relationships between traffic flow stability and model parameters are derived for an entire class of second-order macroscopic traffic flow models. Numerical results axe obtained using the CLAWPACK package for the well-known Payne-Whitham model, in order to illustrate the stability criterion. The newly derived stability results are consistent with previous reported results obtained using both microscopic models and approximate linearization methods. Moreover, the stability criteria derived in the paper can provide more refined information regarding the propagation of traffic flow perturbations and shock waves in second-order models than previously established methodologies.