arXiv subjects

Boris S. Kerner

Publications and source records attributed to Boris S. Kerner.

26 records · Page 2Linked to original sources

arXiv2006

Deterministic approach to microscopic three-phase traffic theory

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 (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.

physics.soc-ph↗

arXiv2005

Microscopic features of moving traffic jams

Empirical and numerical microscopic features of moving traffic jams are presented. Based on a single vehicle data analysis, it is found that within wide moving jams, i.e., between the upstream and downstream jam fronts there is a complex microscopic spatiotemporal structure. This jam structure consists of alternations of regions in which traffic flow is interrupted and flow states of low speeds associated with "moving blanks" within the jam. Empirical features of the moving blanks are found. Based on microscopic models in the context of three-phase traffic theory, physical reasons for moving blanks emergence within wide moving jams are disclosed. Structure of moving jam fronts is studied based in microscopic traffic simulations. Non-linear effects associated with moving jam propagation are numerically investigated and compared with empirical results.

physics.soc-ph↗

arXiv2005

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

A microscopic criterion for distinguishing synchronized flow and wide moving jam phases in single vehicle data measured at a single freeway location is presented. Empirical local congested traffic states in single vehicle data measured on different days are classified into synchronized flow states and states consisting of synchronized flow and wide moving jam(s). Then empirical microscopic characteristics for these different local congested traffic states are studied. Using these characteristics and empirical spatiotemporal macroscopic traffic phenomena, an empirical test of a microscopic three-phase traffic flow theory is performed. Simulations 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. It is found that microscopic three-phase traffic models can explain both microscopic and macroscopic empirical congested pattern features. It is obtained that microscopic 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 it 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.

physics.soc-ph↗

arXiv2005

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

A nucleation model for the breakdown phenomenon in freeway free traffic flow at an on-ramp bottleneck is presented. This model, which can explain empirical results on the breakdown phenomenon, is based on assumptions of three-phase traffic theory in which the breakdown phenomenon is related to a first-order phase transition from the "free flow" phase to the "synchronized flow" phase. The main idea of this nucleation model is that random synchronized flow nucleation occurs within a metastable inhomogeneous steady state associated with a deterministic local perturbation in free flow, which can be considered "deterministic vehicle cluster" in free flow at the bottleneck. This deterministic vehicle cluster in free flow is motionless and exists permanent at the bottleneck due to the on-ramp inflow. In the nucleation model, traffic breakdown nucleation occurs through a random increase in vehicle number within this deterministic vehicle cluster, if the amplitude of the resulting random vehicle cluster exceeds some critical amplitude. The mean time delay and the associated nucleation rate of speed breakdown at the bottleneck are found and investigated. The nucleation rate of traffic breakdown as a function of the flow rates to the on-ramp and upstream of the bottleneck is studied. The nucleation model and the associated results exhibit qualitative different characteristics than those found earlier in other traffic flow nucleation models. Boundaries for speed breakdown in the diagram of congested patterns at the bottleneck are found. These boundaries are qualitatively correlated with numerical results of simulation of microscopic traffic flow models in the context of three-phase traffic theory.

cond-mat.stat-mech↗

arXiv2003

Dependence of Empirical Fundamental Diagram on Spatial-Temporal Traffic Patterns Features

It is shown that the branch of the empirical fundamental diagram for congested traffic strongly depends both on the type of the congested pattern at a freeway bottleneck and on the freeway location where the fundamental diagram is measured. Since the type of the pattern at the same bottleneck can depend on traffic demand, a qualitative form of the empirical fundamental diagram can strong depend on traffic demand also. At freeway locations where the average speed in synchronized flow is higher the branch of the fundamental diagram for congested traffic has a positive slope in the flow density plane as well the slope of the branch for free flow. In the upstream direction when the average synchronized flow speed inside the congested pattern decreases, first the slope of the branch for congested traffic decreases and then the branch can transform into the curve with a maximum. At freeway locations, where the average speed in synchronized flow further decreases the branch for congested traffic more and more tends to the line J which represents the stationary motion of the downstream front of a wide moving jam in the flow-density plane: The line J is an asymptote for the branch of congested traffic of the empirical fundamental diagrams at higher densities for those freeway locations where wide moving jams occur and propagate.

cond-mat.stat-mech↗

arXiv2003

Control of Spatial-Temporal Congested Traffic Patterns at Highway Bottlenecks

A microscopic theory of control of spatial-temporal congested traffic pattern at freeway bottlenecks is presented. Based on empirical spatial-temporal features of congested patterns at freeway bottlenecks which have recently been found, different control strategies for prevention or reducing of the patterns are simulated and compared. The studied control strategies include the on-ramp metering with feedback and automatic cruise control (ACC) vehicles. A recent microscopic traffic flow model within the author's three-phase traffic theory is used for validation of spatial-temporal congested pattern control.

cond-mat.stat-mech↗

arXiv2003

Three-Phase Traffic Theory and Highway Capacity

Hypotheses and some results of the three-phase traffic theory by the author are compared with results of the fundamental diagram approach to traffic flow theory. A critical discussion of model results about congested pattern features which have been derived within the fundamental diagram approach to traffic flow theory and modelling is made. The empirical basis of the three-phase traffic theory is discussed and some new spatial-temporal features of the traffic phase "synchronized flow" are considered. A probabilistic theory of highway capacity is presented which is based on the three-phase traffic theory. In the frame of this theory, the probabilistic nature of highway capacity in free flow is linked to an occurrence of the first order local phase transition from the traffic phase "free flow" to the traffic phase "synchronized flow". A numerical study of congested pattern highway capacity based on simulations of a KKW cellular automata model within the three-phase traffic theory is presented. A congested pattern highway capacity which depends on features of congested spatial-temporal patterns upstream of a bottleneck is studied.

cond-mat.stat-mech↗

arXiv2002

Cellular automata approach to three-phase traffic theory

The cellular automata (CA) approach to traffic modeling is extended to allow for spatially homogeneous steady state solutions that cover a two dimensional region in the flow-density plane. Hence these models fulfill 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 the one 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 [B. S. Kerner and S. L. Klenov. 2002. J. Phys. A: Math. Gen. 35, L31]. These features are qualitatively different than 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.

cond-mat.stat-mech↗