Sergey L. Klenov

Cellular automata approach to three-phase traffic theory

The cellular automata (CA) approach to traffic modelling is extended to allow for spatially homogeneous steady state solutions that cover a two-dimensional region in the flow–density plane. Hence these models fulfil a basic postulate of a three-phase traffic theory proposed by Kerner. This is achieved by a synchronization distance, within which a vehicle always tries to adjust its speed to that of the vehicle in front. In the CA models presented, the modelling of the free and safe speeds, the slow-to-start rules as well as some contributions to noise are based on the ideas of the Nagel–Schreckenberg-type modelling. It is shown that the proposed CA models can be very transparent and still reproduce the two main types of congested patterns (the general pattern and the synchronized flow pattern) as well as their dependence on the flows near an on-ramp, in qualitative agreement with the recently developed continuum version of the three-phase traffic theory (Kerner B S and Klenov S L 2002 J. Phys. A: Math. Gen. 35 L31 ). These features are qualitatively different from those in previously considered CA traffic models. The probability of the breakdown phenomenon (i.e. of the phase transition from free flow to synchronized flow) as function of the flow rate to the on-ramp and of the flow rate on the road upstream of the on-ramp is investigated. The capacity drops at the on-ramp which occur due to the formation of different congested patterns are calculated.

Deterministic microscopic three-phase traffic flow models

Two different deterministic microscopic traffic flow models, which are in the context of the Kerner’s there-phase traffic theory, are introduced. In an acceleration time delay model (ATD-model), different time delays in driver acceleration associated with driver behaviour in various local driving situations are explicitly incorporated into the model. Vehicle acceleration depends on local traffic situation, i.e., whether a driver is within the free flow, or synchronized flow, or else wide moving jam traffic phase. In a speed adaptation model (SAmodel), vehicle speed adaptation occurs in synchronized flow depending on driving conditions. It is found that the ATDand SA-models show spatiotemporal congested traffic patterns that are adequate with empirical results. In the ATDand SA-models, the onset of congestion in free flow at a freeway bottleneck is associated with a first-order phase transition from free flow to synchronized flow; moving jams emerge spontaneously in synchronized flow only. Differences between the ATDand SA-models are studied. A comparison of the ATDand SA-models with stochastic models in the context of three phase traffic theory is made. A critical discussion of earlier traffic flow theories and models based on the fundamental diagram approach is presented. Deterministic approach to microscopic three-phase traffic theory 2Two different deterministic microscopic traffic flow models, which are in the context of the Kerners there-phase traffic theory, are introduced. In an acceleration time delay model (ATD model), different time delays in driver acceleration associated with driver behaviour in various local driving situations are explicitly incorporated into the model. Vehicle acceleration depends on local traffic situation, i.e., whether a driver is within the free flow or synchronized flow or else wide moving jam traffic phase. In a speed adaptation model (SA model), vehicle speed adaptation occurs in synchronized flow depending on driving conditions. It is found that the ATD and SA models show spatiotemporal congested traffic patterns that are adequate with empirical results. In the ATD and SA models, the onset of congestion in free flow at a freeway bottleneck is associated with a first-order phase transition from free flow to synchronized flow; moving jams emerge spontaneously in synchronized flow only. Differences between the ATD and SA models are studied. A comparison of the ATD and SA models with stochastic models in the context of three-phase traffic theory is made. A critical discussion of earlier traffic flow theories and models based on the fundamental diagram approach is presented.

Spatial–temporal patterns in heterogeneous traffic flow with a variety of driver behavioural characteristics and vehicle parameters

A microscopic theory of spatial–temporal congested traffic patterns in heterogeneous traffic flow with a variety of driver behavioural characteristics and vehicle parameters is presented. A microscopic model for heterogeneous traffic flow is developed based on three-phase traffic theory. Diverse congested pattern features at a freeway bottleneck due to an on-ramp in heterogeneous traffic flow on a two-lane freeway are found. A numerical study of these specific pattern features and their comparison with empirical results are performed. A comparison of congested patterns in heterogeneous traffic flow with congested patterns in traffic flow with identical vehicles is made.

Testbed for wireless vehicle communication: a simulation approach based on three-phase traffic theory

A testbed for wireless vehicle communication based on a microscopic model in the framework of three-phase traffic theory is presented. In this testbed, vehicle motion in traffic flow and analyses of a vehicle communication channel access based on IEEE 802.11e mechanisms, radio propagation modeling, message reception characteristics as well as all other effects associated with ad-hoc networks are integrated into a three-phase traffic flow model. Thus simulations of both vehicle ad-hoc network and traffic flow are integrated onto a single testbed and perform simultaneously. This allows us to make simulations of ad-hoc network performance as well as diverse scenarios of the effect of wireless vehicle communications on traffic flow during simulation times, which can be comparable with real characteristic times in traffic flow. In addition, the testbed allows us to simulate cooperative vehicle motion together with various traffic phenomena, like traffic breakdown at bottlenecks. Based on simulations of this testbed, some statistical features of ad-hoc vehicle networks as well as the effect of C2C communication on increase in the efficiency and safety of traffic are studied.

Criterion for traffic phases in single vehicle data and empirical test of a microscopic three-phase traffic theory

Based on empirical and numerical microscopic analyses, the physical nature of a qualitatively different behaviour of the wide moving jam phase in comparison with the synchronized flow phase—microscopic traffic flow interruption within the wide moving jam phase—is found. A microscopic criterion for distinguishing the synchronized flow and wide moving jam phases in single vehicle data measured at a single freeway location is presented. Based on this criterion, empirical microscopic classification of different local congested traffic states is performed. Simulations made show that the microscopic criterion and macroscopic spatiotemporal objective criteria lead to the same identification of the synchronized flow and wide moving jam phases in congested traffic. Microscopic models in the context of three-phase traffic theory have been tested based on the microscopic criterion for the phases in congested traffic. It is found that microscopic three-phase traffic models can explain both microscopic and macroscopic empirical congested pattern features. It is obtained that microscopic frequency distributions for vehicle speed difference as well as fundamental diagrams and speed correlation functions can depend on the spatial co-ordinate considerably. It turns out that microscopic optimal velocity (OV) functions and time headway distributions are not necessarily qualitatively different, even if local congested traffic states are qualitatively different. The reason for this is that important spatiotemporal features of congested traffic patterns are lost in these as well as in many other macroscopic and microscopic traffic characteristics, which are widely used as the empirical basis for a test of traffic flow models, specifically, cellular automata traffic flow models.

Probabilistic Breakdown Phenomenon at On-Ramp Bottlenecks in Three-Phase Traffic Theory

A nucleation model for the breakdown phenomenon at an on-ramp bottleneck is presented. This model is based on Kerners three-phase traffic theory. In this theory, traffic breakdown is associated with a first-order phase transition from the free-flow phase to the synchronized-flow phase. It is suggested that because of merging of a flow on the main road with an on-ramp inflow, free flow is spatially nonhomogeneous in the neighborhood of a bottleneck. This permanent and motionless nonhomogeneity can be considered a deterministic vehicle cluster localized at the bottleneck. Because of the deterministic cluster, the breakdown phenomenon can also occur if there were no fluctuations in free flow. At a lower flow rate, traffic breakdown nucleation occurs through a random increase in vehicle number within the deterministic vehicle cluster. The mean time delay and the associated nucleation rate of traffic breakdown at the bottleneck were found and investigated. The model and a nucleation rate of traffic breakdown ...

Common traffic congestion features studied in USA, UK, and Germany based on kerner's three-phase traffic theory

Based on real traffic data measured on American, UK and German freeways, we study Kerners common features of traffic congestion phases (synchronized flow and wide moving jam) relevant for many transportation engineering applications. General features of traffic congestion, i.e., features of traffic breakdown and of the further development of congested regions, are shown on freeways in the USA and UK beyond the previously known data examples. For the testing of Kerners “line J”, representing the propagation of the wide moving jams downstream front, four different methods are studied and compared for each congested traffic situation occurring in the three countries.

Physical properties of a transverse high-frequency gas discharge. I. Basic properties and physical model of the discharge

Experimental and theoretical investigations of a transverse HF discharge are carried out. A physical model of the discharge is proposed which accounts for the entire range of experimentally observed properties of such a discharge. The features of electron density and temperature radial distributions, spontaneous radiation intensity, laser radiation gain factor in the discharge plasma are covered. Part II covers the stability and uniformity of the discharge plasma column at high values of the discharge current and the conditions of formation and shape of the spatially nonuniform structures arising in the plasma as a result of decreasing discharge current.

A Study of Phase Transitions on Multilane Roads in the Framework of Three-Phase Traffic Theory:

A numerical study of phase transitions in traffic flow on multilane roads in the framework of three-phase traffic theory is presented. It was found that when vehicle merging became easier at a bottleneck, wide moving jams emerged more frequently in synchronized flow upstream of the bottleneck. Depending on the traffic phase and lane-changing probability, lane changing was responsible for qualitatively opposite effects, such as congested traffic dissolution or, in contrast, the emergence of nuclei for traffic breakdown and moving jam emergence. It was found that at a sequence of closely located adjacent bottlenecks, phase transitions between different road lanes resulted in nonregular spatiotemporal traffic dynamics.

Physical properties of a transverse high-frequency gas discharge. II. Spatially non-uniform states in the discharge plasma

For pt.I see ibid., vol.25, no.10, p.1454-60 (1992). On the the basis of the physical model of transverse high-frequency (HF) discharge presented in part I, the stability of a uniform discharge at high values of the HF discharge current is examined. Conditions for the discharge plasma column to break up into plasma filaments are determined and the physics of contraction with decreasing discharge current is considered. Numerical simulation of spatially nonuniform structures in transverse HF discharge is carried out. The results of this simulation describe adequately the experimentally observed plasma distributions in such a discharge.