Showing papers on "Traffic wave published in 2007"

Jam-Avoiding Adaptive Cruise Control (ACC) and its Impact on Traffic Dynamics

Abstract: Adaptive-Cruise Control (ACC) automatically accelerates or decelerates a vehicle to maintain a selected time gap, to reach a desired velocity, or to prevent a rear-end collision To this end, the ACC sensors detect and track the vehicle ahead for measuring the actual distance and speed difference Together with the own velocity, these input variables are exactly the same as in car-following models The focus of this contribution is: What will be the impact of a spreading of ACC systems on the traffic dynamics? Do automated driving strategies have the potential to improve the capacity and stability of traffic flow or will they necessarily increase the heterogeneity and instability? How does the result depend on the ACC equipment level?

Freeway Traffic Shockwave Analysis: Exploring NGSIM Trajectory Data

Abstract: The paper presents the development and application of a numerical algorithm to estimate the propagation speed of shockwaves on freeways based on vehicle trajectory data. The essence of the algorithm is that the shockwave propagation speed is the traveling speed of local minima of consecutive vehicle speed trajectories. The application of the algorithm on the NGSIM datasets from the I-80 and US101 freeways under congested conditions shows that all the shockwaves have similar propagation speed of about 11.4 mph (18.34 kph), which is independent of the traffic flow speed prior to congestion. The algorithm developed here is generic and can be used for shockwave analysis based on any vehicle-by-vehicle trajectories estimated from any range sensors. The findings have been applied to estimate the upper bound for time delay error in link travel time estimation from point sensor data.

Multiclass first-order simulation model to explain non-linear traffic phenomena

Abstract: With the first-order traffic model of Lighthill, Whitham and Richard (LWR), many simple traffic problems can be represented analytically such as a shock formation. However, the LWR model has some deficiencies. For example, among the other things, it fails to replicate interesting non-linear phenomena such as hysteresis and capacity drop as well as the dispersion of traffic platoon when there exists a distribution of desired speeds in heterogeneous traffic. To this end, in this paper, we propose a novel multiclass first-order simulation model based on an approximation of Riemann solver. In the developed model, each vehicle class is only characterized by their desired speeds in a free-flow traffic state where overtaking is allowed. However, when traffic is congested, all vehicle classes must travel at the same congested speed and overtaking is not possible. Numerical results show that the proposed model is not only more accurate and reliable than the existing models but also able to explain non-linear traffic phenomena on freeways.

Generic Second Order Traffic Flow Modelling

Abstract: This paper presents a generic second order family, which generalizes the Aw-Rascle-Zhang (ARZ) model. This family, called Extended Aw-Rascle-Zhang (EARZ) is characterized by a variable fundamental diagram, by the presence along car trajectories of an invariant related to the fundamental diagram, and by a wide scatter of traffic data in the congested domain. It is shown that the resolution methods developed for the ARZ model can be suitably extended to the EARZ family. A bi-phase traffic flow model introduced by Colombo is shown to be close to a model belonging to the EARZ family. The properties of this model are easily deduced from those of the EARZ models.

Observing freeway ramp merging phenomena in congested traffic

Abstract: This paper describes a comprehensive investigation of traffic behavior and characteristics during freeway ramp merging under congested traffic conditions. On the Tokyo Metropolitan Expressway (TME), traffic congestion often occurs at merging bottleneck sections, especially during heavy traffic demand. The TME public corporation usually applies different empirical strategies to increase the flow rate and decrease the accident rate at merging sections. However, these strategies do not rely either on any behavioral characteristics of the merging traffic or on the geometric design of the merging segments. There have been only a few research publications concerned with traffic behavior and characteristics in these situations. Therefore, a 3-year study was conducted to study traffic behavior/characteristics during the merging process under congested situations. Extensive traffic data capturing a wide range of traffic and geometric information was collected using detectors, videotaping, and surveys at 8 interchanges on the TME. Maximum discharged flow rate from the head of the queue at merging sections in conjunction with traffic and geometric characteristics was analyzed. In addition, lane changing maneuvers with respect to freeway and ramp traffic behaviors were examined. It is believed that this study provides a thorough understanding of freeway ramp merging dynamics. It also forms a comprehensive database for the development and implementation of congestion management techniques at merging sections utilizing Intelligent Transportation Systems.

Empirical test of a microscopic three-phase traffic theory

Abstract: A review of dynamic nonlinear features of spatiotemporal congested patterns in freeway traffic is presented. The basis of the review is a comparison of theoretical features of the congested patterns that are shown by a microscopic traffic flow model in the context of the Kerner's three-phase traffic theory and empirical microscopic and macroscopic pattern characteristics measured on different freeways over various days and years. In this test of the microscopic three-phase traffic flow theory, a model of an "open" road is applied: Empirical time-dependence of traffic demand and drivers' destinations are used at the upstream model boundaries. At downstream model boundary conditions for vehicle freely leaving a modeling freeway section(s) are given. Spatiotemporal congested patterns emerge, develop, and dissolve in this open freeway model with the same types of bottlenecks as those in empirical observations. It is found that microscopic three-phase traffic models can explain all known macroscopic and microscopic empirical congested pattern features (e.g., probabilistic breakdown phenomenon as a first-order phase transition from free flow to synchronized flow, moving jam emergence in synchronized flow rather than in free flow, spatiotemporal features of synchronized flow and general congested patterns at freeway bottlenecks, intensification of downstream congestion due to upstream congestion at adjacent bottlenecks). It turns out that microscopic optimal velocity (OV) functions and time headway distributions are not necessarily qualitatively different, even if local congested traffic behavior is qualitatively different. Model performance with respect to spatiotemporal pattern emergence and evolution cannot be tested using these traffic characteristics. The reason for this is that important spatiotemporal features of congested traffic patterns are lost in these and many other macroscopic and microscopic traffic characteristics, which are widely used as the empirical basis for a test of traffic flow models.

Self-Organized Network Flows

Abstract: A model for traffic flow in street networks or material flows in supply networks is presented, that takes into account the conservation of cars or materials and other significant features of traffic flows such as jam formation, spillovers, and load-dependent transportation times. Furthermore, conflicts or coordination problems of intersecting or merging flows are considered as well. Making assumptions regarding the permeability of the intersection as a function of the conflicting flows and the queue lengths, we find self-organized oscillations in the flows similar to the operation of traffic lights.

Microsimulation based corrections on the road traffic noise emission near intersections

Abstract: Urban noise mapping traditionally involves the use of a traffic simulation model, which is often based on the estimation of macroscopic traffic flows. However, intersections and other local traffic management measures are not always modeled correctly. It is well known that the specific deceleration and acceleration dynamics of traffic at junctions can influence local noise emission. Finding the best strategy for using traffic modeling results in noise mapping is a current topic of research in the IMAGINE project. In this paper, a case study is presented, consisting of a large set of microscopic traffic simulations and associated noise emission calculations, which provides some insight into the specific dynamics of the noise emission near different types of intersections. It will be shown that it is possible to refine current traffic noise prediction models, based on macroscopic traffic simulation, using a correction on the average vehicle emission, aggregated in lane segments. A spatial approach should be used, in which inbound and outbound lanes are divided into deceleration, queuing, stopline and acceleration zones. Results from regression analysis on the numerical simulations indicate that meaningful relations between noise corrections and traffic flow parameters such as traffic intensity and composition can be deduced.

Traffic planning for non-homogeneous traffic

Abstract: Traffic on Indian roads (both urban and inter-urban) consists of a variety of vehicles. These vehicles have widely different static and dynamic characteristics. The traffic is also very different from homogeneous traffic which primarily consists of motorized vehicles. Homogeneous traffic follows strict lane discipline as compared to non-homogeneous traffic. Western traffic planning methodologies mostly address the concerns of homogeneous traffic and therefore often prove inadequate in solving problems involving non-homogeneous traffic conditions as found in Indian cities. This paper presents studies conducted on non-homogeneous traffic. Section 1 presents a methodology to verify the continuity equation, the basic block of any traffic planning analysis. In § 2, the methodology developed is applied to modify the Highway Capacity Manual (HCM) 2000 density method to derive passengercar equivalencies (PCEs) or units (PCUs) for heavy vehicles and recreational vehicles. These PCUs appear as ‘ET’ and ‘ER’ in HCM tables. The density method assumes motorized, four-wheeler traffic, i.e., homogeneous traffic, and does not include motorized three-wheelers, motorized two-wheelers, and non-motorized traffic often present on Indian highways. By modifying the density method to represent non-homogeneous traffic, which includes significant percentages of motorized, three-wheelers, motorized two-wheelers, and non-motorized traffic entities, one can derive more accurate passenger car units for Indian conditions. Transport professionals can use these PCU values for accurate capacity, safety, and operational analysis of highways carrying non-homogeneous traffic.

Experimental Features and Characteristics of Speed Dispersion in Urban Freeway Traffic

Abstract: Characteristics of speed dispersion in urban freeway traffic are presented. Two definitions of speed dispersion are proposed: the standard deviation of the individual speeds and the average speed difference of two neighboring vehicles. On the basis of the definitions, traffic data obtained from two urban freeways in China are studied, and different characteristics of speed dispersion are found in four substates of traffic flow, which correspond to four regions in the empirical fundamental diagram. In the bunching state of congested traffic, the flow rate decreases with an increase in speed dispersion at a given mean speed. In the bunching state of fluid traffic, the speed dispersion of traffic flow is small, and in the free state of fluid traffic, speed dispersion is distributed in a disorderly manner in a wide range. Such phenomena are more remarkable under the definition of the average speed difference for speed dispersion. In addition, some possible explanations are presented for the characteristics of speed dispersion in each traffic substate. These speed dispersion studies provide a new approach for microscopic modeling and understanding of traffic flow characteristics.

Analysis of Density Wave in Two-Lane Traffic

Abstract: We use the car-following model (Phys. Rev. E 72 (2005) 066124) to further analyse the two-lane traffic waves. Our numerical results show that in the two-lane traffic, there exist triangular shock, soliton wave and kink wave which appear in the stable, mestastable and unstable regions of headway-sensitivity space, respectively. Compared with the single-lane traffic, it is found that the lateral distance has little effect on the formation of triangular shock and soliton wave although the lateral distance can enlarge the stable region and can reduce the mestastable and unstable regions.

Vehicular traffic through a sequence of green-wave lights

Abstract: We study the vehicular traffic through a sequence of traffic lights on a highway, where signals turn on and off periodically with the green-wave strategy. We present the dynamical model of vehicular traffic controlled by green-wave signals, where a vehicle is inhibited to pass other vehicles. The dynamical behavior of vehicular traffic is clarified by analyzing tour time and traffic pattern. The dependence of tour time on offset time is derived for various values of cycle time. It is found that the tour time at the green-wave strategy is related to that at the synchronized strategy. Also, the dependence of maximal current on both offset time and cycle time is shown.

Travel Time Cost Functions For Urban Roads:A Case Study In Italy

Abstract: This paper describes how cost functions are commonly used in traffic assignment in order to account for the effects of congestion on road link performances. Despite their influence on assignment results, not many effective functions are available for urban roads. Indeed, the effects of congestion on the travel time required to cross an urban link have often been considered negligible in comparison with those on delays at intersections. Nonetheless, traffic flow disturbances like side-parking can appreciably affect link travel time with the rise in congestion, especially in the roads of ancient centers in historical cities. Hence this paper presents a travel time function for urban road links that includes the effect of side-parking, secondary streets and road winding on the worsening of performance due to congestion. Model parameter identification was based both on empirical and experimental data, the latter having been obtained by means of a calibrated micro-simulation model. Cross-validation results do not exclude the possibility of applying the proposed function to different urban areas.

Towards a practical application of model predictive control to suppress shock waves on freeways

Abstract: We present the results of the application of model predictive control (MPC) to a micro-simulation model with a scenario where shock waves are present, and a microsimulation model functions as a substitute for the real-world traffic system. Shock waves emerge in most cases from traffic jams at bottlenecks, propagate upstream on the freeway, and can remain existent for a long time and distance. This increases travel time, is potentially unsafe, and increases noise and air pollution.

Traffic congestion and dispersion in Hurricane evacuation

Abstract: We study the traffic congestion and dispersion of vehicles occurring on a single lane highway in Hurricane evacuation. The traffic congestion depends on both sensitivity and speed of the leading vehicle. When the leading vehicle moves with low speed, the vehicular traffic exhibits the stop and go-wave (oscillating congested traffic) for low sensitivity, while the traffic results in the homogeneous congested traffic for high sensitivity. The traffic dispersion is measured by the time difference between the leading and rear vehicles. The time difference fluctuates highly for the oscillating congestion traffic, while it keeps a constant value for the homogeneous congested traffic. The traffic states in Hurricane evacuation is connected to the phase diagram of conventional traffic.

Traffic Behavior in a Two-Lane System Consisting of a Mixture of Buses and Cars

Abstract: In this paper, a two-lane traffic system consisting of a mixture of buses and cars is studied. The buses stop at each bus stop to pick up passengers and are not allowed to change lane. The cars may change lane when hindered by preceding vehicles. Our simulations show that with a fixed number of buses, four states of the traffic system are identified. The spatial-temporal plots of the four traffic states, and the trajectories of buses at different densities are presented. A gradual transition instead of sharp phase transition from bunching state to homogeneous state of the buses is found. Next, we study the system behavior at different number of bus stops, and an optimal number of stops is suggested. Finally, the influence of bus stops on the fundamental diagram is studied.

A kinematic wave dynamic network loading model, including intersection delays

Abstract: This paper presents a method for including intersection delays in a flow-based traffic model. The original Multi-Commodity Link Transmission Model (MC LTM), a Dynamic Network Loading (DNL) model that is consistent with kinematic wave theory, is extended with delayed urban intersection models. Travel time as a function of traffic load becomes a monotonically increasing function, which is a desirable property in view of equilibrium calculation in DTA.

Heterogeneous Traffic Flow Model for a Two-Lane Roundabout and Controlled Intersection

Abstract: Modern urban traffic management depends heavily on the efficiency of road features, such as controlled intersections and multi-lane roundabouts. Vehicle throughput at any such configuration is modified by traffic mix, by rules governing manoeuvrability and by driver observance, as well as by traffic density. Here, we study heterogeneous traffic flow on two-lane roads through a cellular automata model for a binary mix of long and short vehicles. Throughput is investigated for a range of arrival rates and for fixed turning rate at an intersection: manoeuvres, while described in terms of left-lane driving, are completely generalisable. For a given heterogeneous distribution of vehicle type, there is a significant impact on queue length, delay times experienced and throughput at a fixed-cycle traffic light controlled two-way intersection and two-lane roundabout, when compared to the homogeneous case. As the proportion of long vehicles increases, average throughput for both configurations declines for increasing arrival rate, with average queue length and waiting time correspondingly increased. The effect is less-marked for the two-lane roundabout, due to absence of cross-traffic delays. Nevertheless, average waiting times and queue lengths remain uniformly high for arrival rates >0.25 vehicle per second (900 vph) on entry roads and for long vehicle proportion above 0.30–0.35.

Development of Transportation Systems

Abstract: Road systems 1 , railway systems 2 , air traffic systems 3 , and, for example, container vessel shipping 4 , all share underlying abstractions such as transportation nets with hubs (road intersections, train stations, airports and harbours) and links (road segments, train tracks, air and sea lanes) and their states of being open or closed for certain flows of traffic across hubs and along links, etc. In this paper we shall first hint at an abstract formal model for such transportation and then show how it can be refined into models for road traffic, train traffic and air traffic. Then we likewise hint at how such, so-called domain models — which reflect only what there is ”out there”, in reality, before computing and communication — can be rigorously transformed into requirements for respective traffic monitoring and control s The paper concludes with a discussion of issues of development of the right systems, that is, the systems that customers (that is, transportation and traffic authorities) expect to receive, and of systems which are right, that is, are correct.

System and method based on short range wireless communications for notifying drivers of abnormal road traffic conditions

Abstract: The present invention predicts traffic conditions based on traffic information exchanged by means of short range wireless communications, between vehicles moving in an opposite direction. A method in accordance with an embodiment of the present invention includes: successively recording traffic information based on traffic encountered by the vehicle; sending the traffic information to vehicles moving in the opposite direction; receiving traffic information from vehicles moving in the opposite direction; consolidating the traffic information received from the vehicles; and predicting traffic conditions based on the consolidated traffic information.

Traffic information calculation device, traffic information calculation program and traffic information calculation method

Abstract: PROBLEM TO BE SOLVED: To accurately decide traffic information such as a traffic jam degree by considering waiting for a traffic light to change to obtain an accurate travel time when obtaining travel time information by use of information of a probe vehicle. SOLUTION: Position/speed data of the vehicle traveling in a road section are collected (S1), a traffic light waiting time and a frequency of the waiting for the traffic light to change in the road section of the vehicle are calculated based on a collected speed V of the vehicle (S6), and the traffic light waiting time is subtracted from the travel time of the road section (S8) to calculate the net travel time of the road section, and the traffic information such as the traffic jam degree of the road section is decided based on the net travel time (S10). COPYRIGHT: (C)2009,JPO&INPIT

System and method for radio wave based vehicle-to-vehicle spreading of road traffic information

Abstract: The present invention relates to a system and a method for radio wave based vehicle-to-vehicle spreading of road traffic information, wherein each of the vehicles (101-104) is provided with a radio transmitter, a radio receiver, a location positioning device and a message forwarding timer. The method comprises the steps of recognizing, by a first vehicle (101), a road traffic event occurred on a section of a road (105) on which said first vehicle is travelling; generating, by said first vehicle, a piece of road traffic information relating to the road traffic event; generating, by said first vehicle, a first road trajectory description information including at least data for the identification of said road section; generating, by said first vehicle, a first message containing at least a unique identifier for said message, said piece of road traffic information, the location of the vehicle sending the first message, said location being determined by its location positioning device, and said first road trajectory description information; transmitting, by said first vehicle, said first message by radio message spreading; receiving, by at least one second vehicle (102,103,104).

An Exact Graph Structure for Dynamic Traffic Assignment: Formulation, Properties, and Computational Experience

Abstract: The objective of this paper is to present an exact graph structure for dynamic traffic assignment (DTA), thereby providing a clear theoretical bridge between dynamic traffic assignment and graph theory. An exact graph-based formulation (GBF) with origins in the cell transmission model (CTM) is presented for the single destination DTA problem. The “cell” concept is formalized and projected in graph theoretic terms, leading to the graph theoretic cell transmission model (GTCTM). The fundamental difference with the CTM and existing DTA formulations (linear, minimum cost flow sub-structure) is in the modeling of backward propagating traffic waves, which is extensively discussed. The system optimal (SO) and the user equilibrium (UE) traffic assignment objectives are modeled on the same graph structure with modified weights. Properties of the corresponding graph are recognized: (i) the GBF is acyclic, and (ii) every edge-disjoint path is also a node-disjoint path. The existence of a solution and the property of uniqueness are analyzed using the GTCTM basis. Experimental results indicate significant benefits in computational time; it is the direct outcome of reducing the complexity of a linear formulation to minimum cost flow.

Behaviours in a dynamical model of traffic assignment with elastic demand

Abstract: This paper investigates the dynamical behaviour of network traffic flow. Assume that trip rates may be influenced by the level of service on the network and travellers are willing to take a faster route. A discrete dynamical model for the day-to-day adjustment process of route choice is presented. The model is then applied to a simple network for analysing the day-to-day behaviours of network flow. It finds that equilibrium is arrived if network flow consists of travellers not very sensitive to the differences of travel cost. Oscillations and chaos of network traffic flow are also found when travellers are sensitive to the travel cost and travel demand in a simple network.

Traffic mixing in deterministic two-lane model of Hurricane evacuation

Abstract: We study the mixing of vehicles on a two-lane highway in Hurricane evacuation. We present the deterministic model of two-lane traffic in which vehicles change the lane by a deterministic rule. We investigate the typical traffic induced by a slow vehicle on the first lane under the open boundary. The escape time of vehicles is determined by their order. The vehicular order changes by traffic mixing. The traffic mixing depends highly on the sensitivity. For high sensitivity, the escape time depends on the initial order of vehicles. For low sensitivity, the lane changing occurs irregularly by stop- and go-waves and vehicles then evacuate irregularly without keeping their initial order.

Locating the Variable Message Signs by Cell Transmission Model

Abstract: With the development of intelligent transportation technologies, the variable message signs (VMS) have been widely used in guiding and managing the dynamic traffic. It is known that cell transmission model (CTM) can well reproduce such traffic dynamics as shock waves and jams. This paper employs the CTM to study the location problem of VMS. Simulation results show that there exists an optimal VMS location to minimize the total travel time of the traffic system. How changes of route choice probabilities before and after a traffic accident affect the optimal VMS locations is also investigated and it is concluded that the VMS should be placed far from the accident site if the anticipated accident is very serious.

Biham–middleton–levine traffic model with origin-destination trips

Abstract: We extended the Biham–Middleton–Levine model to incorporate the origin and destination effect of drivers trips on the traffic in cities. The destination sites are randomly chosen from some origin-destination distances probability distribution "ODDPD." We use three different distributions: exponential, uniform, and power-law. We found that the traffic dynamics of the model are greatly influenced by the ODDPD. Moreover, it is found that we can adjust the ODDPD to enhance the road capacity of the city and to minimize the arrival times of drivers.

The Effect of Noise-First and Anticipation Headway on Traffic Flow

Abstract: This article considers the interplay of noise and traffic flow. The authors introduce anticipation headway to modify the noise-first NaSch model under the conditions of periodic boundary. They used mathematical simulation to examine the traffic situation with different parameters. They found that the Noise-First model with added anticipation headway is more realistic in reflecting traffic flow, including start-stop wave, synchronized flow, and also the metastable state. The modified model can reproduce nonlinear phenomena which agrees with the real traffic flow.

Traffic signal controller, program, and method

Abstract: PROBLEM TO BE SOLVED: To calculate the optimal signal parameter to cancel traffic congestion at an intersection, by grasping the traffic congestion circumstances of a road leading to the intersection based on probe information collected from a probe vehicle. SOLUTION: In a traffic control center 5, probe information, including the information of the location and speed of a vehicle at every traveling time is collected, and the traffic congestion tailing location of a road leading to the intersection is grasped based on the collected probe information, and the optimal green signal time of each traffic light 6 is controlled so that traffic congestion of the intersection is solved from the traffic congestion tailing location of each road that connects to the intersection. COPYRIGHT: (C)2009,JPO&INPIT