30 research outputs found
Theoretical predictions for vehicular headways and their clusters
This article presents a derivation of analytical predictions for steady-state
distributions of netto time gaps among clusters of vehicles moving inside a
traffic stream. Using the thermodynamic socio-physical traffic model with
short-ranged repulsion between particles (originally introduced in [Physica A
\textbf{333} (2004) 370]) we firstly derive the time-clearance distribution in
the model. Consecutively, the statistical distributions for the so-called time
multi-clearances are calculated by means of theory of functional convolutions.
Moreover, all the theoretical surmises used during the above-mentioned
calculations are proven by the statistical analysis of traffic data. The
mathematical predictions acquired in this paper are thoroughly compared with
relevant empirical quantities and discussed in the context of three-phase
traffic theory.Comment: 23 pages, 10 figure
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.Comment: 19 pages, 12 figure
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.Comment: 27 pages, 16 figure