39 research outputs found
Parallel Implementations of Cellular Automata for Traffic Models
The Biham-Middleton-Levine (BML) traffic model is a simple two-dimensional,
discrete Cellular Automaton (CA) that has been used to study self-organization
and phase transitions arising in traffic flows. From the computational point of
view, the BML model exhibits the usual features of discrete CA, where the state
of the automaton are updated according to simple rules that depend on the state
of each cell and its neighbors. In this paper we study the impact of various
optimizations for speeding up CA computations by using the BML model as a case
study. In particular, we describe and analyze the impact of several parallel
implementations that rely on CPU features, such as multiple cores or SIMD
instructions, and on GPUs. Experimental evaluation provides quantitative
measures of the payoff of each technique in terms of speedup with respect to a
plain serial implementation. Our findings show that the performance gap between
CPU and GPU implementations of the BML traffic model can be reduced by clever
exploitation of all CPU features
Non-concave fundamental diagrams and phase transitions in a stochastic traffic cellular automaton
Within the class of stochastic cellular automata models of traffic flows, we
look at the velocity dependent randomization variant (VDR-TCA) whose parameters
take on a specific set of extreme values. These initial conditions lead us to
the discovery of the emergence of four distinct phases. Studying the
transitions between these phases, allows us to establish a rigorous
classification based on their tempo-spatial behavioral characteristics. As a
result from the system's complex dynamics, its flow-density relation exhibits a
non-concave region in which forward propagating density waves are encountered.
All four phases furthermore share the common property that moving vehicles can
never increase their speed once the system has settled into an equilibrium
Energy Dissipation Burst on the Traffic Congestion
We introduce an energy dissipation model for traffic flow based on the
optimal velocity model (OV model). In this model, vehicles are defined as
moving under the rule of the OV model, and energy dissipation rate is defined
as the product of the velocity of a vehicle and resistant force which works to
it.Comment: 15 pages, 19 Postscript figures. Reason for replacing: This is the
submitted for
Performance Evaluation of Road Traffic Control Using a Fuzzy Cellular Model
In this paper a method is proposed for performance evaluation of road traffic
control systems. The method is designed to be implemented in an on-line
simulation environment, which enables optimisation of adaptive traffic control
strategies. Performance measures are computed using a fuzzy cellular traffic
model, formulated as a hybrid system combining cellular automata and fuzzy
calculus. Experimental results show that the introduced method allows the
performance to be evaluated using imprecise traffic measurements. Moreover, the
fuzzy definitions of performance measures are convenient for uncertainty
determination in traffic control decisions.Comment: The final publication is available at http://www.springerlink.co
Spring-block model for a single-lane highway traffic
A simple one-dimensional spring-block chain with asymmetric interactions is
considered to model an idealized single-lane highway traffic. The main elements
of the system are blocks (modeling cars), springs with unidirectional
interactions (modeling distance keeping interactions between neighbors), static
and kinetic friction (modeling inertia of drivers and cars) and spatiotemporal
disorder in the values of these friction forces (modeling differences in the
driving attitudes). The traveling chain of cars correspond to the dragged
spring-block system. Our statistical analysis for the spring-block chain
predicts a non-trivial and rich complex behavior. As a function of the disorder
level in the system a dynamic phase-transition is observed. For low disorder
levels uncorrelated slidings of blocks are revealed while for high disorder
levels correlated avalanches dominates.Comment: 6 pages, 7 figure
Urban traffic from the perspective of dual graph
In this paper, urban traffic is modeled using dual graph representation of
urban transportation network where roads are mapped to nodes and intersections
are mapped to links. The proposed model considers both the navigation of
vehicles on the network and the motion of vehicles along roads. The road's
capacity and the vehicle-turning ability at intersections are naturally
incorporated in the model. The overall capacity of the system can be quantified
by a phase transition from free flow to congestion. Simulation results show
that the system's capacity depends greatly on the topology of transportation
networks. In general, a well-planned grid can hold more vehicles and its
overall capacity is much larger than that of a growing scale-free network.Comment: 7 pages, 10 figure
Metric properties of discrete time exclusion type processes in continuum
A new class of exclusion type processes acting in continuum with synchronous
updating is introduced and studied. Ergodic averages of particle velocities are
obtained and their connections to other statistical quantities, in particular
to the particle density (the so called Fundamental Diagram) is analyzed
rigorously. The main technical tool is a "dynamical" coupling applied in a
nonstandard fashion: we do not prove the existence of the successful coupling
(which even might not hold) but instead use its presence/absence as an
important diagnostic tool. Despite that this approach cannot be applied to
lattice systems directly, it allows to obtain new results for the lattice
systems embedding them to the systems in continuum. Applications to the traffic
flows modelling are discussed as well.Comment: 27 pages, 4 figures; minor errors corrected; details added to proofs
of Theorems 4.1 and 5.
Chaotic asymptotic behaviour of the solutions of the Lighthill Whitham Richards equation
[EN] The phenomenon of chaos has been exhibited in mathematical nonlinear models that describe traffic flows, see, for instance (Li and Gao in Modern Phys Lett B 18(26-27):1395-1402, 2004; Li in Phys. D Nonlinear Phenom 207(1-2):41-51, 2005). At microscopic level, Devaney chaos and distributional chaos have been exhibited for some car-following models, such as the quick-thinking-driver model and the forward and backward control model (Barrachina et al. in 2015; Conejero et al. in Semigroup Forum, 2015). We present here the existence of chaos for the macroscopic model given by the Lighthill Whitham Richards equation.The authors are supported by MEC Project MTM2013-47093-P. The second and third authors are supported by GVA, Project PROMETEOII/2013/013Conejero, JA.; MartÃnez Jiménez, F.; Peris Manguillot, A.; Ródenas Escribá, FDA. (2016). Chaotic asymptotic behaviour of the solutions of the Lighthill Whitham Richards equation. 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