Showing papers on "Traffic wave published in 2001"

Traffic and related self-driven many-particle systems

Abstract: Since the subject of traffic dynamics has captured the interest of physicists, many surprising effects have been revealed and explained. Some of the questions now understood are the following: Why are vehicles sometimes stopped by ``phantom traffic jams'' even though drivers all like to drive fast? What are the mechanisms behind stop-and-go traffic? Why are there several different kinds of congestion, and how are they related? Why do most traffic jams occur considerably before the road capacity is reached? Can a temporary reduction in the volume of traffic cause a lasting traffic jam? Under which conditions can speed limits speed up traffic? Why do pedestrians moving in opposite directions normally organize into lanes, while similar systems ``freeze by heating''? All of these questions have been answered by applying and extending methods from statistical physics and nonlinear dynamics to self-driven many-particle systems. This article considers the empirical data and then reviews the main approaches to modeling pedestrian and vehicle traffic. These include microscopic (particle-based), mesoscopic (gas-kinetic), and macroscopic (fluid-dynamic) models. Attention is also paid to the formulation of a micro-macro link, to aspects of universality, and to other unifying concepts, such as a general modeling framework for self-driven many-particle systems, including spin systems. While the primary focus is upon vehicle and pedestrian traffic, applications to biological or socio-economic systems such as bacterial colonies, flocks of birds, panics, and stock market dynamics are touched upon as well.

Optimizing traffic lights in a cellular automaton model for city traffic.

Abstract: We study the impact of global traffic light control strategies in a recently proposed cellular automaton model for vehicular traffic in city networks. The model combines basic ideas of the Biham-Middleton-Levine model for city traffic and the Nagel-Schreckenberg model for highway traffic. The city network has a simple square lattice geometry. All streets and intersections are treated equally, i.e., there are no dominant streets. Starting from a simple synchronized strategy, we show that the capacity of the network strongly depends on the cycle times of the traffic lights. Moreover, we point out that the optimal time periods are determined by the geometric characteristics of the network, i.e., the distance between the intersections. In the case of synchronized traffic lights, the derivation of the optimal cycle times in the network can be reduced to a simpler problem, the flow optimization of a single street with one traffic light operating as a bottleneck. In order to obtain an enhanced throughput in the model, improved global strategies are tested, e.g., green wave and random switching strategies, which lead to surprising results.

MASTER: macroscopic traffic simulation based on a gas-kinetic, non-local traffic model

Abstract: We present a gas-kinetic (Boltzmann-like) traffic equation that is not only suited for low vehicle densities, but also for the high-density regime, as it takes into account the forwardly directed interactions, effects of vehicular space requirements like increased interaction rates, and effects of velocity correlations that reflect the bunching of cars, at least partially. From this gas-kinetic equation, we systematically derive the related macroscopic traffic equations. The corresponding partial differential equations for the vehicle density and average velocity are directly related to the quantities characterizing individual driver–vehicle behavior, and, as we show by calibration of the model, their optimal values have the expected order of magnitude. Therefore, the model allows to investigate the influences of varying street and weather conditions or freeway control measures. We point out that, because of the forwardly directed interactions, the macroscopic equations contain non-local instead of diffusion or viscosity terms. This resolves some of the inconsistencies found in previous models and allows for a fast and robust numerical integration, so that several thousand freeway kilometers can be simulated in real-time. It turns out that the model is in good agreement with the experimentally observed properties of freeway traffic flow. In particular, it reproduces the characteristic outflow and dissolution velocity of traffic jams, as well as the phase transition to “synchronized” congested traffic. We also reproduce the five different kinds of congested states that have been found close to on-ramps (or bottlenecks) and present a “phase diagram” of the different traffic states in dependence of the main flow and the ramp flow, showing that congested states are often induced by perturbations in the traffic flow. Finally, we introduce generalized macroscopic equations for multi-lane and multi-userclass traffic. With these, we investigate the differences between multi-lane simulations and simulations of the effective one-lane model.

Complexity of Synchronized Flow and Related Problems for Basic Assumptions of Traffic Flow Theories

Abstract: A review of an experimental study of traffic phases and phase transitions in traffic flow is presented. A critical comparison of model results with real features of traffic phases is given. A qualitative theory of congested traffic which has recently been developed is discussed.

Preferred time-headway of highway drivers

Abstract: The preferred time-headway of drivers in highway conditions is related to the likelihood of rear-end collisions. We studied traffic data from a section of southbound highway 101- a heavily commuted eight-lane freeway between San Francisco and the Silicon valley in California. We observed two parameters that drivers regulate during free flow, rush hour, and heavy traffic conditions: (1) the speed of their vehicle; and (2) the time-headway to the preceding vehicle. During free flow traffic, the preferred speeds show low variation within lanes, but large variations from lane to lane. During rush hour traffic, the time-headway between vehicles varies between 1 and 2 s for a range of traffic speeds. For all traffic conditions a lower limit of 1s is seen in time-headway, even when traffic volume does not push drivers toward tight spacing. The lower limit of 1s is consistent with what was found in several previous studies, but is significantly shorter than the 3s headway that is recommended by driving manuals. The short time-headways observed are within the limit of typical reaction time for braking by alert drivers, but probably lead to occasional accidents given variability in reaction times, decisions, and vehicle braking capabilities, especially when preview information is not available.

Microsimulations of freeway traffic including control measures

Abstract: This paper describes how speed limits, ramp metering, and vehicle- based driver support systems were studied for their influence on freeway traffic by using a microscopic traffic model. Simulation results for a section of the German Autobahn indicated that speed limit and ramp metering were able to reduce congestion considerably while introducing 20% of the vehicles that were equipped with driver support systems almost completely eliminated congestion.

Mixed Manual/Semi-Automated Traffic: A Macroscopic Analysis

Abstract: The use of advanced technologies and intelligence in vehicles and infrastructure could make the current highway transportation system much more efficient. Semi-automated vehicles with the capability of automatically following a vehicle in front as long as it is in the same lane and in the vicinity of the forward looking ranging sensor are expected to be deployed in the near future. Their penetration into the current manual traffic will give rise to mixed manual/semi-automated traffic. In this paper, we analyze the fundamental flow-density curve for mixed traffic using flow-density curves for 100% manual and 100% semi-automated traffic. Assuming that semi-automated vehicles use a time headway smaller than today's manual traffic average due to the use of sensors and actuators, we have shown using the flow-density diagram that the traffic flow rate will increase in mixed traffic. We have also shown that the flow-density curve for mixed traffic is restricted between the flow-density curves for 100% manual and 100% semi-automated traffic. We have presented in a graphical way that the presence of semi-automated vehicles in mixed traffic propagates a shock wave faster than in manual traffic. We have demonstrated that the presence of semi-automated vehicles does not change the total travel time of vehicles in mixed traffic. Though we observed that with 50% semi-automated vehicles a vehicle travels 10.6% more distance than a vehicle in manual traffic for the same time horizon and starting at approximately the same position, this increase is marginal and is within the modeling error. Lastly, we have shown that when shock waves on the highway produce stop-and-go traffic, the average delay experienced by vehicles at standstill is lower in mixed traffic than in manual traffic, while the average number of vehicles at standstill remains unchanged.

Some observed details of freeway traffic evolution

Abstract: Certain details of traffic evolution were studied along a 2 km, homogenous freeway segment located upstream of a bottleneck. By comparing (transformed) cumulative curves constructed from the vehicle counts measured at neighboring loop detectors, it was found that waves propagated through queued traffic like a random walk with predictable statistical variation. There was no observed dependency of wave speed on flow. As such, these waves neither focused nor fanned outward and shocks arose only at the interfaces between free-flowing traffic and the back of queues. Although these traffic features may have long been suspected, actual observations of this kind have hitherto not been documented. Also of note, the shocks separating queued and unqueued traffic sometimes exhibited unexpectedly long transitions between these two states. Finally, some observations presented here corroborate earlier reports that, in unqueued traffic, vehicle velocity is insensitive to flows and that forward-moving changes in traffic states therefore travel with vehicles. Taken together, these findings suggest that certain rather simple models suffice for describing traffic on homogeneous freeway segments; brief discussion of this is offered in Section 5.

Analysis of Time Headways on Urban Roads: Case Study from Riyadh

Abstract: The headway between vehicles in a traffic stream is of fundamental importance in traffic engineering applications. Previous research in this subject has focused on modeling theoretical distributions for low and medium traffic flow conditions. Yet little research has studied congested traffic conditions—that is, the high traffic flow state. In the same context, there appears to be a lack of clear-cut boundaries for the three flow states (low, medium, and high). This study attempts to determine such boundaries on the basis of traffic conditions observed at the study sites. Although observed headways at arterial sites follow a gamma distribution, distributions that fit freeway headways differ according to the traffic flow state. The Erlang distribution provided a good fit to the observed headways at sites with high traffic flows.

Method of presuming traffic conditions by using floating car data and system for presuming and presenting traffic conditions by using floating data

Abstract: A method of presuming traffic conditions for implementing a forecast and a presumption of traffic jam situation in an area where probe cars are not traveling currently, in which the probe cars send floating car data that is times and positions of traveled areas to center facilities, and the center accumulates the floating car data in a floating car data database by traffic conditions presumption means and also presumes forecast traffic jam information in the forward areas of the probe cars and presumed traffic jam information in the backward areas thereof by using the current floating car data and the floating car data database accumulated from the past to the present.

Generic gas-kinetic traffic systems modeling with applications to vehicular traffic flow

Abstract: This article presents a generic continuum modeling approach for the description of flow operations for a general class of traffic systems. That is, the traffic flow model presented in this paper models traffic flows independently of the type of traffic (vehicular traffic on motorways or rural roads, pedestrian flows). Key to the approach is the introduction of the so-called generalized phase-space density (g-PSD). This density concept is a generalization of traffic density with respect to both discrete attibutes, such as user-class, roadway lane, and destination, and continuous attributes, such as velocity, and desired velocity. In the approach, we distinguish continuum and non-continuum processes. The continuum processes reflect smooth changes in the g-PSD, while the non-continuum processes describe non-smooth changes in the g-PSD. These non-continuum processes are either caused by events experienced by a traffic entity, or by the condition of a traffic entity. To show the potential of this new and powerful modeling framework, a simple model specification example for platoon-based description of traffic flow is presented.

New Perspectives on Continuum Traffic Flow Models

Abstract: This paper discusses the mathematical properties of two classes of continuum models that extend the basic kinematic wave model of Lighthill and Whitham, and Richards (LWR)—lower-order and higher-order continuum models. While the differences among the discussed models are pointed out and contrasted, the emphasis is on their commonality. In the latter we found that 1) both classes of models, including the basic kinematic wave model, can violate the anisotropic property of traffic flow, 2) both types of models produce waves non-existent in the LWR model, and 3) both lower and higher order models can be reduced to a kinematic wave model with an effective fundamental diagram. It can therefore be said that the two classes of models are much more closely related than their appearances had led people to believe. The paper concludes with a discussion on the treatment of inhomogeneities and a proposal of a proper procedure for experimentally validating any continuum traffic flow models.

Human behavior as origin of traffic phases.

Abstract: It is shown that the desire for smooth and comfortable driving is directly responsible for the occurrence of synchronized traffic in highway traffic. This desire goes beyond the avoidance of accidents, which so far has been the main focus of microscopic modeling and that is mainly responsible for the other two phases observed empirically, free flow and wide moving jams. These features have been incorporated into a microscopic model based on stochastic cellular automata by means of event-driven anticipation. The results of computer simulations are compared with empirical data. It turns out that anticipation effects are responsible for the stabilization of the traffic phases and even reproduce the empirically observed coexistence of wide moving jams with both free flow and synchronized traffic.

Method for traffic situation determination on the basis of reporting vehicle data for a traffic network with traffic-controlled network nodes

Abstract: A method for determining the traffic situation is based on traffic data which are obtained from reporting vehicles moving in the traffic, for a traffic network with traffic-controlled network nodes and roadway sections connecting them. Traffic data indicative of travel times on the roadway sections are obtained by reporting vehicles moving in the traffic, and are used to determine travel times on a roadway-section-specific basis. The mean number of vehicles in the queue, the mean number of vehicles, the mean vehicle speed outside the queue, the mean waiting time in the queue and/or the mean vehicle density outside the queue are determined from these travel times for the respective roadway section.

A realistic description of the environment for inter-vehicle wave propagation modelling

Abstract: The modelling of a realistic environment for road traffic scenarios is presented. The model serves as a basis for a new wave propagation tool for inter-vehicle communications. A proper modelling of the environment implies an accurate characterisation of the dynamic road traffic and a realistic description of the vehicle's vicinity. For an accurate model of dynamic road traffic and realistic driving behaviour, different individual characteristics of vehicles are taken into account. Characteristics such as desired velocity or safety margin are determined stochastically within certain limits. It is therefore possible to create complex traffic scenarios without the need of having detailed and extensive traffic data for selected roads. Additionally, the road surrounding is generated stochastically, depending on morphographic data. The result is a proper traffic scenario, which serves as input data for wave propagation calculations.

The combined traffic assignment and control problem: an overview of 25 years of research

Abstract: This paper describes how, traffic control and traveler's behavior are two processes that influence each other The two processes have different 'actors' who can have different goals The road manager will try to achieve a network optimum and will try to control traffic in such a way that this optimum is reached Tools for controlling traffic control are for example traffic signals, traffic information, ramp metering, etc The optimum can be a system optimum or a preferential treatment for certain user groups, eg public transport or pedestrians The road users will search for their own optimum, eg the fastest or cheapest way to travel from A to B Decisions taken by the road manager in controlling traffic in a certain way have an influence on the possibilities for travelers to choose their preferred mode, route and time of departure, and vice versa A change in traffic control may have the impact that traffic volumes change If for example traffic control is modified such that congestion on a certain route disappears and delays on intersections decrease, traffic might be attracted from other links where congestion still exists or which are parts of a longer route This might have the consequence that, queues, which originally disappeared, return Delays may come back on the original levels The question is then whether there still is a net profit for the traffic system as a whole Another example is that public transport gets priority in intersection control The delay for other road users may increase and thus force these road users to search for other routes, departure times or even transport modes in the network If it is assumed that a modification in traffic control gives a change in travel behavior, it is necessary to anticipate this change If delays are optimized, it should be done for the traffic volumes that will be present after the introduction of the optimized traffic control and not for the traffic volumes, which existed before the implementation Of course, it is possible to follow an interactive approach, where after each shift in traffic volumes the control scheme is adjusted until equilibrium has been reached, or one may use self-adjusting traffic control However, it can be shown, for certain examples, that the process of the adjustment of traffic control, followed by a shift in traffic volumes, does not necessarily lead to a system optimum It is even possible that the system oscillates between two or more states This arises from the fact that the system optimum is not necessarily the same as the user optimum The system optimum is good for the network as a whole, but can be disadvantageous for a part of the travelers in the network The control problem is therefore to optimize traffic control in such a way that the system is at a certain, prescribed optimum, taking into account the reaction of travelers This is called the combined traffic assignment and control problem In one classifies the available literature, a distinction can be made between three different approaches to solve the combined assignment and control problem

Standing waves and the influence of speed limits

Abstract: Traffic dependent speed limits have improved the security of highway traffic considerably. However, on highway sections controlled by variable speed limits large oscillations in speed can still be observed. On the basis of traffic data and a macroscopic traffic model, the influence of decentrally controlled speed limits on the states of highway traffic is analyzed. It is shown that local control of speed limits — which is typically applied — can lead to standing waves in speed. The anticipative control law proposed is able to prevent standing waves and can even damp out stop-and-go waves, such that a homogeneous traffic flow is gained.

Probabilistic Description of Traffic Flow

Abstract: The study of traffic flow is investigated by different means. Well established theories are (i) kinematic models based on partial differential equations to describe traveling density waves, and (ii) deterministic models using nonlinear car‐following equations to determine trajectories of moving cars, as well as (iii) large-scale simulation hopping models like cellular automata. An important intermediate approach is (iv) the stochastic or probabilistic attempt to understand phenomena like “Stau aus dem Nichts” (phantom jam) on long crowded roads. Initiated by the old argument that road traffic is a stochastic process, we develop a new probabilistic theory based on Markov processes to improve our understanding of traffic flow and its three phases (free flow, synchronized motion, wide moving jams) discovered by Kerner. As an introductory example, first we consider a dissolution of a car queue described by the stochastic master equation as a one-step decay process. Furtheron more realistic models are developed to investigate the nucleation, growth and condensation as well as dissolution of car clusters on a circular one-lane freeway. In analogy to usual aggregation phenomena such as the formation of liquid droplets in supersaturated vapour the clustering behavior in traffic flow is described by the master equation. At overcritical densities the transition from the initial free particle situation (free flow of vehicles) to the final congested state, where one or several big aggregates of cars have been formed, is shown. In dependence on the concentration of cars on the road the stationary solution of the master equation is derived analytically. The obtained fundamental diagram as flow-density-relation indicates clearly the different regimes of traffic flow (free jet of cars, coexisting phase of jams and isolated cars, highly viscous heavy traffic). In the (thermodynamic) limit of infinite number of vehicles on an infinite long road the analytical solution for the fundamental diagram is in agreement with experimental traffic flow data. As a particular example we take into account measurements from German highways presented by Kerner and Rehborn.

Traffic flow forecasting

Abstract: This paper presents a review of methods used to perform dynamic traffic forecasting. New models for tracing and forecasting of congested spatial-temporal patterns on highways are examined. These include ASDA (automatic tracing of moving traffic jams) and FOTO (Forecasting of traffic objects). The advantage of these models is that they allow for the tracing and prediction of macroscopic spatial-temporal properties of traffic patterns without any validation of model parameters at different conditions. In addition, a macroscopic model for dynamic traffic forecasting in urban areas is described. The model, which allows for the prediction of macroscopic characteristics of traffic (such as queue lengths at traffic signals and link travel times), is shown to have a calculation time that can be several thousand times shorter than that of a microscopic traffic model.

Method for determining the traffic state in a traffic network with effective bottlenecks

Abstract: A method for determining the traffic state in a traffic network with effective bottlenecks with a classification at least into the “freely flowing traffic”, “synchronized traffic” and “moving widespread congestion” state phases and into patterns of dense traffic upstream of effective bottlenecks. FCD traffic data which includes information relating to the location and the speed of the vehicle is recorded at time intervals for a respective route section, and by reference to the information it is determined whether an effective bottleneck is present. If this is the case, from the current FCD traffic data, a pattern of dense traffic, which fits it, is continuously determined as a currently present pattern of dense traffic.

Generalised processor sharing networks fed by heavy-tailed traffic flows

Abstract: We consider networks where traffic is served according to the generalised processor sharing (GPS) principle. GPS-based scheduling algorithms are considered important for providing differentiated quality of service in integrated-services networks. We are interested in the workload of a particular flow i at the bottleneck node on its path. Flow i is assumed to have long-tailed traffic characteristics. We distinguish between two traffic scenarios, (i) flow i generates instantaneous traffic bursts and (ii) flow i generates traffic according to an on/off process. In addition, we consider two configurations of feedforward networks. First we focus on the situation where other flows join the path of flow i. Then we extend the model by adding flows which may branch off at any node, with cross traffic as a special case. We prove that under certain conditions the tail behaviour of the workload distribution of flow i is equivalent to that in a two-node tandem network where flow i is served in isolation at constant rates. These rates only depend on the traffic characteristics of the other flows through their average rates. This means that the results do not rely on any specific assumptions regarding the traffic processes of the other flows. In particular, flow i is not affected by excessive activity of flows with 'heavier-tailed' traffic characteristics. This confirms that GPS has the potential to protect individual flows against extreme behaviour of other flows, while obtaining substantial multiplexing gains.

Method of determining traffic situation based on reported vehicle data for traffic network including traffic-controlled network nodes

Abstract: PROBLEM TO BE SOLVED: To provide a method of determining a traffic situation based on the traffic data obtained from a reported vehicle during traveling for a traffic network including traffic-controlled network nodes and a road section for connecting the network nodes. SOLUTION: The traffic data indicating the time of movement through the road distance can be provided from the reported vehicle during traveling. From the data, the movement time is determined for each point in the road section and, from the movement time an average number of vehicles in a queue, an average number of vehicles an average speed of vehicles outside a queue, an average standby time in a queue, and/or an average density of vehicles outside a queue are determined for each road section. Particularly, the actual traffic situation based on FCD for the road traffic network in a densely inhabited area is re-constructed, and the traffic prediction can be performed based on the re-construction.

A model for estimating traffic delays and vehicle queues at freeway work zones

Abstract: In order to efficiently plan and schedule work zone operations, it is essential to accurately estimate traffic delays. This article presents the results of a study on traffic delays at work zones on Indiana freeways. The equations for calculating various components of traffic delays are described and the applications of these equations are illustrated. Traffic delays at a work zones can be caused by deceleration while approaching the work zone, reduced vehicle speed through the area, and time needed for vehicles to resume freeway speed after exiting the vehicle queues. Delay equations were developed in this study when arrival traffic flow is above the work zone capacity and below it. In calculating traffic delays, the vehicle queue-discharge rates, instead of the work zone capacity, should be used because the queue-discharge rates are lower than the work zone capacity. Equations related to individual vehicle queues were also developed to estimate the queue lengths, the time needed to clear vehicles from a queue, and the total and average traffic delays of a queue. The quantities of these vehicle queue attributes can be used to display real-time traffic information on message signs to inform motorists of expected delays or for adaptive traffic controls at work zones.

Development and Evaluation of the Lane Merge Traffic Control System at Construction Work Zones

Abstract: The majority of safety hazards and resulting traffic crashes that occur in lane closure areas in work zone are often due to the aggressive behavior of some drivers. The late lane merge phenomenon occurs when some drivers try to avoid slow moving traffic by traveling in the lane that is about to end, and then attempt to force merge in the through lane at the last moment. In an attempt to alleviate such aggressive driver behavior at work zones an innovative traffic control system was tested in Michigan. The Michigan Department of Transportation (MDOT) began a pilot project to study the effectiveness of a lane merge traffic control system (LMTCS), creating an enforceable no passing zone to encourage motorists to make an early merge. In Phase I of this study, test and control sites were examined in order to evaluate the effectiveness of the Michigan LMTCS, in terms of reducing delay, driver behavior and the effects of police enforcement. The research efforts for Phase II involved the development of an optimal traffic control system for work zone lane merges based on the experiences of the Phase I study and field testing of the same. During the Phase II, a comparison of the before and after data indicated that for similar flow rates, the average speeds increased. This may be due to the smoother traffic flow created by the dynamic LMTCS. Also, the average delay per vehicle to pass through the work zone and the number of aggressive driving maneuvers decreased due to the LMTCS.

Stochastic modeling and real-time estimation of incident effects on surface street traffic congestion

Abstract: Real-time prediction of the effects of arterial incidents on traffic congestion is a significant factor in the development of advanced incident management systems. This paper explores a stochastic modeling approach to real-time prediction of incident effects on surface traffic congestion. To formulate the incident-induced traffic congestion problems for surface street arterial incident cases, inter-lane and intra-lane traffic variables are specified, followed by the development of a discrete-time, nonlinear stochastic model and a recursive estimation algorithm for the application of real-time prediction. The proposed method is tested with simulated data generated using the Paramics traffic simulator The preliminary tests indicated the capability of the proposed method in estimating incident effects on surface street traffic congestion in real time. We expect that this study can provide realtime incident-related traffic information with benefits not only for understanding the impact of incidents on non-recurrent traffic congestion of surface streets, but also for developing advanced incident-responsive traffic control and management technologies.

Judgment method of traffic state in traffic network having effective obstacle factor

Abstract: PROBLEM TO BE SOLVED: To provide a means for judging a traffic state in a traffic network having an effective obstacle factor. SOLUTION: This method comprises classifying the traffic state in the traffic network having the effective obstacle factor to at least each state phase of 'traffic state of running without limitation', 'traffic state of synchronous running' and 'moving extensive traffic jam', and classifying the traffic state into a high density traffic pattern including these state phases formed on the upper stream of the effective obstacle factor. An FCD traffic data formed of information related to the position and speed of a vehicle is recorded in respective route parts at time intervals, and the presence of the effective obstacle factor is judged in reference to the information. When the effective obstacle factor is present, the high density traffic pattern matched thereto is continuously judged from the present FCD traffic data as the present high density traffic pattern. This method is used, for example, for the judgment of a traffic state including the prediction of traffic state in a road traffic network. COPYRIGHT: (C)2002,JPO

The Wonderful World of Active Many-Particle Systems

Abstract: Since the subject of traffic dynamics has captured the interest of physicists, many astonishing effects have been revealed and explained. Some of the questions now understood are the following: Why are vehicles sometimes stopped by so-called “phantom traffic jams”, although they all like to drive fast? What are the mechanisms behind stop-and-go traffic? Why are there several different kinds of congestion, and how are they related? Why do most traffic jams occur considerably before the road capacity is reached? Can a temporary reduction of the traffic volume cause a lasting traffic jam? Why do pedestrians moving in opposite directions normally organize in lanes, while nervous crowds are “freezing by heating”? Why do panicking pedestrians produce dangerous deadlocks? All these questions have been answered by applying and extending methods from statistical physics and non-linear dynamics to self-driven many-particle systems.

Can't get there from here--or can we?

Abstract: The traffic planning process, with models forecasting travel demand based on solid demographic data and sophisticated simulation, often makes traffic problems worse. This is due to the process's inability to recognize that new road capacity itself induces more travel. This paper discusses the induced travel effect in detail, including the endless loop of road widenings and extensions followed by waves of induced traffic congestion. Ending the loop by not increasing road capacity will not lead to gridlock, political upheaval or loss of business as commonly feared. Instead, there will be a series of gradual, most beneficial, adjustments. Drivers will move their travel away from the most congested times, find alternative routes and reinvest in their urban neighborhoods rather than moving to suburban homes. More, smaller commercial destinations would be developed rather than fewer large ones. Other potential consequences of not building additional capacity are discussed.