Showing papers on "Traffic wave published in 2005"

On a Paradox of Traffic Planning

Abstract: For each point of a road network, let there be given the number of cars starting from it, and the destination of the cars. Under these conditions one wishes to estimate the distribution of traffic flow. Whether one street is preferable to another depends not only on the quality of the road, but also on the density of the flow. If every driver takes the path that looks most favorable to him, the resultant running times need not be minimal. Furthermore, it is indicated by an example that an extension of the road network may cause a redistribution of the traffic that results in longer individual running times.

Traffic state detection with floating car data in road networks

Abstract: A method for a reporting behavior at optimal costs of single vehicles (FCD: floating car data) in road networks with the aim of a high quality of traffic state recognition is presented. It is shown that based on minimum two FCD messages the substantial information of a typical traffic incident in a traffic center can be recognized. The two relevant periods of such an obstruction of traffic in road networks are the periods, in which either a travel time increase takes place due to congestion emergence or a travel time decrease because of congestion dissolution. A statistic analysis already shows the high quality of the reconstruction of the actual travel times in the net with 1.5% equipped FCD vehicles and a reduction of the FCD message sending of the vehicles by suppression of redundant incident information. Incidents with at least 20 min duration can be recognized with a probability of 65% with an penetration rate of 1.5% FCD vehicles within the whole amount of vehicles, whereby the FCD vehicles send only in each incident case two messages per event.

Method for refining traffic flow data

Abstract: Traffic information, including traffic flow information and traffic incident information, obtained through a traffic management system for providing and facilitating the exchange of traffic information between a remote location and a vehicle may be presented to a user on a user display in the vehicle. In one embodiment, traffic information provided to a vehicle navigation device is refined by comparing the average speed of the vehicle against the average speed of other vehicles traveling along the same road. In another embodiment, the operation of a traffic signal is controlled based, in part, on the current traffic flow and distance from the traffic signal to alleviate traffic congestion.

Influence of Bus Stops on Flow Characteristics of Mixed Traffic

Abstract: The number and type of bus stops provided on a road significantly influence the flow characteristics of traffic on the road. The study of the influence of bus stops on traffic flow under homogeneous traffic conditions has been attempted by several researchers. However, studies on the influence of bus stops on traffic flow under heterogeneous traffic conditions, are found to be absent. This paper is concerned with the study of heterogeneous traffic flow characteristics using a simulation technique with specific reference to the influence of bus stops on the traffic flow. First, an overview of the microscopic traffic-flow simulation model used to study the flow characteristics of nonlane-based heterogeneous traffic on urban road links is given. Then, the validation of the model based on field observed data is described. Finally, the application of the model to study the impact of curbside bus stops and bus bays on the speeds of other vehicles in heterogeneous traffic streams is dealt with. The effects of variation of the basic parameters, such as bus dwell time, road width, and traffic flow level, are examined for both curbside and bus bay type of stops. The usefulness of the model in fixing the traffic flow levels for replacing curbside stops with bus bays, as example, has also been highlighted.

Self-Organized Control of Irregular or Perturbed Network Traffic

Abstract: We present a fluid-dynamic model for the simulation of urban traffic networks with road sections of different lengths and capacities The model allows one to efficiently simulate the transitions between free and congested traffic, taking into account congestion-responsive traffic assignment and adaptive traffic control We observe dynamic traffic patterns which significantly depend on the respective network topology Synchronization is only one interesting example and implies the emergence of green waves In this connection, we will discuss adaptive strategies of traffic light control which can considerably improve throughputs and travel times, using self-organization principles based on local interactions between vehicles and traffic lights Similar adaptive control principles can be applied to other queueing networks such as production systems In fact, we suggest to turn push operation of traffic systems into pull operation: By removing vehicles as fast as possible from the network, queuing effects can be most efficiently avoided The proposed control concept can utilize the cheap sensor technologies available in the future and leads to reasonable operation modes It is flexible, adaptive, robust, and decentralized rather than based on precalculated signal plans and a vulnerable traffic control center

Traffic circles and timing of traffic lights for cars flow

Abstract: In this paper we address the following traffic regulation problem: given a junction with some incoming roads and some outgoing ones, is it preferable to regulate the flux via a traffic light or via a traffic circle on which the incoming traffic enters continuously? More precisely, assuming that drivers distribute on outgoing roads according to some known coefficients, our aim is to understand which solution performs better from the point of view of total amount of cars going through the junction. To deal with this problem we consider a fluid dynamic model for traffic flow on a road network. The model is that proposed in [9] and is applied to the case of crossings with lights and with circles. For the first we consider timing of lights as control and determine the asymptotic fluxes. For the second we extend and complete the model of [9] introducing some right of way parameters. Also in this case we determine the asymptotic behavior. We then compare the performances of the two solutions. Finally, we can indicate which choice is preferable, depending on traffic level and control necessity, and give indications on how to tune traffic light timing and traffic circle right of way parameters.

Transportation and traffic theory flow, dynamics and human interaction: proceedings of the 16th International Symposium on Transportation and Traffic Theory, University of Maryland, College Park, Maryland, 19-21 July 2005

Abstract: Bilevel optimisation of prices in a variety of transportation models. A sequential experimental approach for analyzing second-best road pricing with unknown demand functions. Highway inventory control system. Path size and overlap in multi-modal transport networks. Pedestrian dynamics and evacuation: empirical results and design solutions. An empircal assessment of traffic operations. Reliability of freeway traffic flow: a stochastic concept of capacity. A critical comparison of the kinematic-wave model with observational data. Average velocity of waves propagating through congested freeway traffic. Microscopic three-phase traffic theory and its applications for freeway traffic control. Behavioural approach to instability, stop and go waves, wide jams and capacity drop. Controlling traffic breakdowns. Parameter estimation and analysis of car-following models. Modeling Impatience of drivers in passing maneuvers. A simulation model for motorway merging behaviour. Freeway ramp merging process observed in congested traffic: lag vehicle acceleration model. A first-order macroscopic traffic flow model for mixed traffic including moving bottleneck effects. A variational formulation of kinematic waves: bottleneck properties and examples. First-order macroscopic traffic flow models: intersection modeling, network modelling. Real-time estimation of travel times on signalized arterials. Calibration and validation of dynamic traffic assignment systems. Non-equilibrium dynamic traffic assignment. Precision of predicted travel time, the responses of travellers, and satisfaction in the travel experience. Behavioral dynamics in activity participation, travel, and information and communications technology. Modeling the joint labor-commute engagement decisions of San Francisco Bay Area residents. A model of daily time use allocation using fractional logit methodology. Efficient estimation of nested logit models using choice-based samples. Functional approximations to alternative-specific constants in time-period choice-modelling. Project-based activity scheduling for person agents. Modelling commercial vehicle empty trips: theory and application. Rationality and heterogeneity in taxi driver decision: application of a stochastic-process model of taxi behavior. A rolling-horizon approach to the optimal dispatching of taxis. Capacitated arc routing problem with extensions. User-equilibrium route set analysis of a large road network. Comparison of static maximum likelihood origin-destination formulations. A time-dependent activity and travel choice model with multiple parking options. Doubly dynamic equilibrium distribution approximation model for dynamic traffic assignment. A combined model of housing location and traffic equilibrium problems in a continuous transportation system.

Traffic states and jamming transitions induced by a bus in two-lane traffic flow

Abstract: We study the traffic states and jamming transitions induced by a bus (slow car) in a two-lane traffic of cars. We use the dynamic model which is an extended one of the optimal velocity model to take into account the lane changing. The fundamental (flow-density) diagram is presented. The fundamental diagram changes highly by introducing a bus on a two-lane roadway. It is found that there are the six distinct states for the two-lane traffic flow including a bus. The spatio-temporal patterns are presented for the distinct traffic states. The dynamical state of traffic changes with density of cars. It is shown that the dynamical transitions among the distinct traffic states occur at some values of density. The phase diagram (region map) is shown for the two-lane traffic flow including a bus.

Cellular automaton traffic flow model considering intelligent transportation system

Abstract: A novel cellular automaton model for traffic flow on highway is proposed considering Intelligent Transportation System (ITS). Based on the Nagel-Schreckenberg model (NS for short), it includes effective gap and brake light. Moreover, a novel concept about the variable security gap is introduced. The simulation shows that the road capacity of the modified ITS cellular automaton model is higher than the measured data on certain highway, further indicating the important role of ITS,enlarged traffic flow and suppressed traffic jam. The mixed traffic flow related to two different vehicles' velocity is studied. The simulation shows even few slow vehicles will lead to drastic decrease of traffic flow, which demonstrates the necessity to implement strictly special fast lane.

Study of traffic flow at an unsignalized T-shaped intersection by cellular automata model

Abstract: In this paper, the traffic flow at an unsignalized T-shaped intersection in which there are three input directions of vehicles and two right-turnings and one left-turning has been investigated by using the cellular automata traffic model. The interactions between vehicles on different lanes and effects of traffic flow states of different roads on capacity of T-shaped intersection system are analyzed. The phase transition characteristics of traffic states on different lanes are studied. The research indicates that the model can be applied to the real traffic analysis and traffic forecast.

A Behavioural Approach to Instability, Stop and Go Waves, Wide Jams and Capacity Drop

Abstract: This paper describes how congested traffic flow dynamics have attracted much interest over the last decade. In order to explain congested traffic flow phenomena, some researchers have stressed the importance and validity of first order hydrodynamic models, while others point out the importance of second order phenomena (instability) for the formation of various congestion patterns, and of local perturbations initiating phase transitions. A macroscopic traffic flow model is used in this paper in order to examine typical congestion related phenomena like traffic flow instability, stop-and-go waves, wide jams, hysteresis, and capacity drop, and the role of driver behavior. The model related individual car-following behavior to macroscopic traffic flow dynamics, and accounts for the principal aspects of individual longitudinal behavior like: finite reaction times, anticipation behavior to conditions downstream (i.e. non-locality and anisotropy), and finite, speed dependent space requirements of drivers. Because of the strong relation with individual human driving behavior and gas-kinetic mathematics that underlies this model, it is called the human-kinetic traffic flow model. Moreover, the parameters that govern the individual driver behavior in the human-kinetic model are not necessary constant in time, but may vary with traffic flow conditions, location, weather, and other conditions. In this sense, the human kinetic traffic flow model is an experimental framework in which the role of variable individual longitudinal driver behavior in macroscopic traffic flow dynamics can be examined.

Average Velocity of Waves Propagating through Congested Freeway Traffic

Abstract: This paper employed cross correlation in order to estimate wave velocities between several successive detector stations during congested periods over a large data set. Given homogeneous vehicles and drivers, the macroscopic model of Lighthill, Whitman and Richards (LWR), predicts that for a convex flow-density relationship all waves should propagate upstream during congested periods. The analysis first employed cumulative arrivals - a functional flow - and then the local traffic speed as the detections stations. It was then shown that the flow-based analysis yielded mixed results, with many measurements being consistent with earlier research, but many more measurements falling outside of the typical range of measured wave velocities from the literature. But vehicles are not homogeneous and it was also shown that flow and occupancy depend on effective vehicle length as well as the local traffic speed. Because the vehicle lengths travel downstream with the vehicles, this information will hinder the attempts to extract wave velocities propagating against the flow traffic when using flow-based measures.

Modeling Traffic Flow and Management at Un-signalized, Signalized and Roundabout Road Intersections

Abstract: Traffic congestion continues to hinder economic and social development and also has a negative impact on the environment. A simple mathematical model is used to analyze the different types of road intersections in terms of their Performance in relation to managing traffic congestion and to establish the condition for stability of the road intersections after sufficiently longer periods of time (steady-state). In the analysis, single and double lane un-signalized, signalized and roundabout intersections are evaluated on the basis of their performance (expected number of vehicles and waiting time). Experimental scenarios are carefully designed to analyze the performance of the different types of intersections. It is noted that under light traffic, roundabout intersections perform better than un-signalized and signalized in terms of easing congestion. However under heavy traffic, signalized intersection perform better in terms of easing traffic congestion compared to un-signalized and roundabout intersections. It is further noted that for stability of a road intersection, the proportion of the time a road link stopping at an intersection is delayed should not exceed the utilization factor (the ratio of the arrival rate of vehicles to the product of number of service channels and service rate).

Single-lane traffic simulation with multi-agent system

Abstract: Agent-based traffic simulation has emerged as an efficient tool to investigate traffic phenomenon. However, the main problem is how to reproduce realistic patterns of traffic flow at both macroscopic and microscopic levels with restricted computational resources. In this paper, we present a multi-agent framework of single-lane traffic simulation. We focus on the driver-vehicle agents, which is the most important ones in the framework. The three-layer architecture of driver-vehicle agents is proposed, the decision tree of tactical longitudinal movement is put forward, and the simplified formulas of acceleration and deceleration rate are derived. With parallel update mode of agent states, a one-dimension traffic simulation model is developed. To validate it at the macroscopic level, we reproduced the realistic flow-density and speed-density relation of traffic flow with periodic boundary condition. To validate it at the microscopic level, a platoon of 10 vehicles was simulated. Given four kinds of typical speed profiles of the leader, each follower can follow its leader safely and stably. The result shows that this model can reproduce realistic macroscopic and microscopic characteristics of single-lane traffic flow.

The Effect of Mixed Vehicles on Traffic Flow in Two Lane Cellular Automata Model

Abstract: In real traffic, the traffic system is usually composed of different types of vehicles, which have different parameters. How these parameters, especially the lengths of the vehicles, influence the traffic behaviors and transportation capability has seldom been investigated. In this paper, we study the mixed traffic system using the cellular automata traffic flow model. The simulation results show that when the road occupancy rate is large, increasing the fraction of long vehicles can apparently, improve the transportation capability. The influence of slow vehicles fraction on the average velocity of vehicles has been discussed, and it is found that the influences are very different when the difference of vehicle length is considered or not.

Improvement of driving safety in road traffic system

Abstract: A road traffic system is a complex system in which humans participate directly. In this system, human factors play a very important role. In this paper, a kind of control signal is designated at a given site (i.e., signal point) of the road. Under the effect of the control signal, the drivers will decrease their velocities when their vehicles pass the signal point. Our aim is to transit the traffic flow states from disorder to order and then improve the traffic safety. We have tested this technique for the two-lane traffic model that is based on the deterministic Nagel–Schreckenberg (NaSch) traffic model. The simulation results indicate that the traffic flow states can be transited from disorder to order. Different order states can be observed in the system and these states are safer.

The German Autobahn: an ITS test bed for examining dynamic traffic flow phenomena

Abstract: Traffic conditions were examined along a 30 km section of northbound Autobahn 5 near Frankfurt, Germany using archived inductive loop detector data. Fifteen bottleneck activations were identified and their reproducible features were described. Bottlenecks became active in the vicinity of on-ramps and off-ramps and once a bottleneck became active, its queue discharge flow was reproducible across multiple activations and across multiple days. The analysis tools used in this study were transformed curves of cumulative vehicle count and cumulative time-mean velocity. These cumulative curves provided the resolution necessary to reveal the spatial and temporal aspects of dynamic freeway traffic flow phenomena. With increasing availability of reliable freeway sensor data, it is important to continue the systematic empirical analysis of freeways in different countries with varying geometric configurations. The results of this research would assist with all aspects of traffic flow modeling, operations and control.

Modeling the effect of heavy vehicles on sign occlusion at multilane highways

Abstract: The research presented in this paper is concerned with modeling the occlusion of ground-mounted traffic signs by heavy vehicles on multilane highways. It is part of a more extensive research effort to examine the different factors that determine the effect of heavy vehicles on the visibility of traffic signs. An analytical tool was developed where road geometry, traffic sign, and moving entities are simulated over space at any point in time. This tool dynamically models the movement and location of passenger cars and trucks on the facility upstream of the subject traffic sign and verifies the continuity of sightline between the subject driver and traffic sign. Besides roadway and sign geometry, the model accounts for other traffic conditions such as traffic level, percentage of trucks, lane utilization, and average speeds of passenger cars and trucks. The occlusion of ground-mounted traffic signs by heavy vehicles is estimated using two measures. The first measure is the probability of a traffic sign being occluded by heavy vehicles under certain traffic and geometric conditions. The second measure estimates the likelihood of a passenger car driver missing the sign based on the minimum time required for the driver to detect, recognize, and read the message.

Bunching and transition of vehicles controlled by a sequence of traffic lights

Abstract: We study the dynamical behavior of many vehicles with different desired velocities, moving through a sequence of traffic lights on a single-lane highway, where the traffic lights turn on and off periodically with the synchronized strategy. The dynamics of vehicular traffic controlled by traffic lights is described in terms of the nonlinear maps. For specific values of cycle time, the group (cluster) of vehicles exhibits the bunching without extending over the highway. It is found that two types of traffic states appear: the one is the bunching traffic and the other is the extended traffic. In the bunching traffic, all vehicles move together with the same tour time, while vehicles spread over the highway in the extended traffic. The dynamical transition between two traffic states occurs at specific values of cycle time. The phase diagram (region map) is presented.

A First-Order Macroscopic Traffic Flow Model for Mixed Traffic Including Moving Bottleneck Effects

Abstract: This paper describes how the Lighthill-Whitham and Richards (LWR) traffic model makes it possible to capture many traffic features. Its simplicity is a major advantage for numerous and various applications and its solution is well known in the industry. However, this model describes the traffic as a continuous and homogeneous flow that is assumed to be in equilibrium states. These hypotheses can be too rough for some traffic situations, in particular from a traffic management point of view. For example, the LWR model considers that all vehicles are identical and that all drivers behave in the same way. This tends to give a rather disappointing description of a heterogeneous traffic flow. Emerging continuum vehicular models attempt to improve the description of the traffic flow given by the LWR model. Two main methods are explored: (1) disaggregating a heterogeneous traffic flow into more homogenous classes and/or considering different lane types; and (2) considering a dynamic relationship between density and speed instead of a fundamental diagram. The research presented in this paper falls under the first method. Indeed, considering homogenous classes could preserve the efficiency of the LWR model for a homogeneous flow while taking into account the traffic composition. Moreover, trucks are numerous and share similar behavior, which justifies modeling them as a fluid.

Cellular automaton model of traffic flow based on safety driving

Abstract: Considering the condition of having a stationary vehicle ahead, a new one-dimensional cellular automaton model emphasizing high safety is proposed to reduce the probability of rear-end collision in the Nagel-Schreckenberg model. The simulation results reveal the presence of metastable state, nonequilibrium phase transition and hysteresis effects, which have been observed in real traffic. Due to the introduction of the safety probability, traffic flow near the critical density will turn to a synchronized flow at low speed, rather than the jam state. So the probability of rear-end collision will be reduced and the traffic capacity may be increased at high traffic density.

Controlling Traffic Breakdowns

Abstract: Traffic breakdowns are described by a balance equation that models the dynamics of jam formation by two contributions: (1) a discharge rate depending on the lenght of the congestion, (2) an adhesion rate mainly depending on the traffic volume of the considered road section. With this balance equation it is feasible to calculate the dynamics of traffic pattern formation especially the first passage time for a transition from free flow condition to congested traffic including the influence of the parameters affecting the discharge and adhesion rates. Findings based on measurements from German freeways are reported for prompting the assumptions. It leads to an easy to operate definition of the capacity of a road section. How speed limits, lane closures, keep in lane recommendations and ramp metering influence the discharge and adhesion rate is discussed both from a theoretical point of view and from field observations exploring freeway sections with and without corridor control systems. Starting with the cumulative probability for breakdowns the change in the incident duration distribution is calculated and qualitatively given. The paper concludes with recommendations for a comprehensive operation improvement and provides necessary steps for a long lasting stabilization of traffic for a given traffic flow time series pattern.

Study on Road Traffic Delay Caused by Bicycle for Mixed Traffic Stream

Abstract: In mixed traffic, non-motorized block interference can cause the delay of road traffic flow, which has not been studied completely because of lacking definite mathematical model and calculation method. Aiming at two-lane road, this paper establishes a model to analyze the delay of road traffic caused by non-motorized for mixed traffic quantitatively. To some extent, this model can be used to evaluate service level of road and determine reasonable road resistance function.

Fluctuation and Transition of Vehicular Traffic Through a Sequence of Traffic Lights

Abstract: We study the dynamical behavior of N vehicles with no passing, but are moving through a sequence of traffic lights on a single-lane highway, where the traffic lights turn on and off periodically with the synchronized strategy. The dynamical model of N vehicles controlled by traffic lights is described in terms of coupled maps with three parameters. The motions of vehicles display a complex behavior, interacting with other vehicles through the sequence of traffic lights. Fluctuation of the leading vehicle is amplified to the following vehicles. The amplification of fluctuation changes with cycle time. The dynamical behavior of vehicles depends highly on their position of grouping vehicles. Signal traffic at a low density changes at specific values of cycle time. The complex dynamical transitions occur by varying three parameters.

Traffic collision cover

Abstract: A traffic collision cover is disclosed which restricts the view of physical damage to one or more vehicles involved in a traffic accident to passing motorists and pedestrians who may slow down and obstruct traffic while observing an accident scene. This invention allows emergency personnel to quickly cover one or more vehicles or parts of vehicles with fabric to hide the damage done in an accident. As a result, this invention helps prevent traffic congestion and increase traffic flow at accident scenes.

A development of traffic prediction system based on real-time simulation

Abstract: The purpose of this research is to develop a traffic prediction system by using the real-time information (vehicle detector, VICS etc) and the existent traffic simulation. It is to watch conditions to change with the time always and to hold traffic control suitably. Recently, a traffic jam happens chronically frequently, and it is a big social problem in the urban expressway. To control this traffic safely and smoothly, it is important to give a plan more rapidly and suitably. We think that this system is useful as an examination and evaluation tool of the policy by predicting future short-term traffic conditions from the present traffic conditions.

Microscopic Three-Phase Traffic Theory and ITS Applications for Freeway Traffic Control

Abstract: This paper describes how there are a huge number of traffic flow theories and models that should explain diverse congested traffic patterns that are observed upstream of freeway bottlenecks. However, it is only recently that a “puzzle” of spatiotemporal features of congested patterns has adequately solved these pattern features. Consequently, earlier traffic flow theories and models that are in a serious conflict with many of these empirical spatiotemporal traffic pattern features. Therefore, the paper introduced “three-phase traffic theory.” In three-phase traffic theory, besides the “free flow” phase there are two phases in congested traffic: “synchronized flow” and “wide moving jam.” Thus, there are three traffic phases in this theory: (1) free flow; (2) synchronized flow; and (3) wide moving jam. Three-phase traffic theory explains the complexity of traffic based on phase transitions among the three traffic phases, and on their complex nonlinear spatiotemporal features.

Qualitative analysis of traffic jam formation in urban ring road

Abstract: In this paper, the procedure of traffic jams formation in urban ring road are studied qualitatively. Some concepts such as homogeneous measure index (HMI) and spatial-temporal difference index (SDI) are utilized to scale the cross-lane inhomogeneities of the traffic flow, and the spatial-temporal state transitions of the traffic flow are explained in terms of HMI and SDI. We present the actual data of Beijing Third Ring Road to describe the procedure of a traffic jam formation, and the concepts proposed in this paper are used to explain the causality of the traffic jam formation.

A New Simulation-Assignment Model DynaTAIWAN for Mixed Traffic Flows

Abstract: This paper presents an integrated dynamic simulation-assignment model, DynaTAIWAN, for Advanced Traffic Management Systems as well as Advanced Traveller Information Systems. The model is composed of two layers, namely simulation-layer and real-time control layer. The simulation is designed to simulate traffic flow patterns according to assumed tripmaker characteristics and/or under a set of given conditions; the real-time control layer receives real-time vehicle information and forecast short-term traffic flow patterns. Four different vehicle types are explicitly considered and modeled in DynaTAIWAN, including car, bus, motorcycle, and truck. Car, trucks, and bus are represented by passenger-car equivalent (PCE) in DynaTAIWAN. Motorcycles are moving along the link through macroscopic flow relationships, and the speed of motorcycles are adjusted to reflect motorcycle characteristics. At intersections, motorcycles are moved according to the sequence of left-turn-waiting section, waiting section, and normal traffic lane. Numerical experiments are conducted in a 50-node test network and a Taichung City Network to explore the dynamic model under real-time information supply strategies.