19 research outputs found
Economics-Based Optimization of Unstable Flows
As an example for the optimization of unstable flows, we present an
economics-based method for deciding the optimal rates at which vehicles are
allowed to enter a highway. It exploits the naturally occuring fluctuations of
traffic flow and is flexible enough to adapt in real time to the transient flow
characteristics of road traffic. Simulations based on realistic parameter
values show that this strategy is feasible for naturally occurring traffic, and
that even far from optimality, injection policies can improve traffic flow.
Moreover, the same method can be applied to the optimization of flows of gases
and granular media.Comment: Revised version of ``Optimizing Traffic Flow'' (cond-mat/9809397).
For related work see http://www.parc.xerox.com/dynamics/ and
http://www.theo2.physik.uni-stuttgart.de/helbing.htm
Traffic flow on realistic road networks with adaptive traffic lights
We present a model of traffic flow on generic urban road networks based on
cellular automata. We apply this model to an existing road network in the
Australian city of Melbourne, using empirical data as input. For comparison, we
also apply this model to a square-grid network using hypothetical input data.
On both networks we compare the effects of non-adaptive vs adaptive traffic
lights, in which instantaneous traffic state information feeds back into the
traffic signal schedule. We observe that not only do adaptive traffic lights
result in better averages of network observables, they also lead to
significantly smaller fluctuations in these observables. We furthermore compare
two different systems of adaptive traffic signals, one which is informed by the
traffic state on both upstream and downstream links, and one which is informed
by upstream links only. We find that, in general, both the mean and the
fluctuation of the travel time are smallest when using the joint
upstream-downstream control strategy.Comment: 41 pages, pdflate
Optimizing Traffic Lights in a Cellular Automaton Model for City Traffic
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.Comment: 13 pages, 10 figure
Coherent Moving States in Highway Traffic (Originally: Moving Like a Solid Block)
Recent advances in multiagent simulations have made possible the study of
realistic traffic patterns and allow to test theories based on driver
behaviour. Such simulations also display various empirical features of traffic
flows, and are used to design traffic controls that maximise the throughput of
vehicles in heavily transited highways. In addition to its intrinsic economic
value, vehicular traffic is of interest because it may throw light on some
social phenomena where diverse individuals competitively try to maximise their
own utilities under certain constraints.
In this paper, we present simulation results that point to the existence of
cooperative, coherent states arising from competitive interactions that lead to
a new phenomenon in heterogeneous highway traffic. As the density of vehicles
increases, their interactions cause a transition into a highly correlated state
in which all vehicles practically move with the same speed, analogous to the
motion of a solid block. This state is associated with a reduced lane changing
rate and a safe, high and stable flow. It disappears as the vehicle density
exceeds a critical value. The effect is observed in recent evaluations of Dutch
traffic data.Comment: Submitted on April 21, 1998. For related work see
http://www.theo2.physik.uni-stuttgart.de/helbing.html and
http://www.parc.xerox.com/dynamics
Intelligent Controlling Simulation of Traffic Flow in a Small City Network
We propose a two dimensional probabilistic cellular automata for the
description of traffic flow in a small city network composed of two
intersections. The traffic in the network is controlled by a set of traffic
lights which can be operated both in fixed-time and a traffic responsive
manner. Vehicular dynamics is simulated and the total delay experienced by the
traffic is evaluated within specified time intervals. We investigate both
decentralized and centralized traffic responsive schemes and in particular
discuss the implementation of the {\it green-wave} strategy. Our investigations
prove that the network delay strongly depends on the signalisation strategy. We
show that in some traffic conditions, the application of the green-wave scheme
may destructively lead to the increment of the global delay.Comment: 8 pages, 10 eps figures, Revte
Optimised Traffic Flow at a Single Intersection: Traffic Responsive signalisation
We propose a stochastic model for the intersection of two urban streets. The
vehicular traffic at the intersection is controlled by a set of traffic lights
which can be operated subject to fix-time as well as traffic adaptive schemes.
Vehicular dynamics is simulated within the framework of the probabilistic
cellular automata and the delay experienced by the traffic at each individual
street is evaluated for specified time intervals. Minimising the total delay of
both streets gives rise to the optimum signalisation of traffic lights. We
propose some traffic responsive signalisation algorithms which are based on the
concept of cut-off queue length and cut-off density.Comment: 10 pages, 11 eps figs, to appear in J. Phys.
Living in Living Cities
This paper presents an overview of current and potential applications of
living technology to some urban problems. Living technology can be described as
technology that exhibits the core features of living systems. These features
can be useful to solve dynamic problems. In particular, urban problems
concerning mobility, logistics, telecommunications, governance, safety,
sustainability, and society and culture are presented, while solutions
involving living technology are reviewed. A methodology for developing living
technology is mentioned, while supraoptimal public transportation systems are
used as a case study to illustrate the benefits of urban living technology.
Finally, the usefulness of describing cities as living systems is discussed.Comment: 40 pages, 4 figures, overview pape
Quartz crystal microbalance gas sensor arrays for the quality control of chocolate
Analysis of chocolate flavour through gas sensor arrays has been carried out. Two different set of sensors have been tested to assess the performance of the different sensor arrays: metallo porphyrins and gold nanoparticles peptide coated quartz crystal microbalances. Two series of chocolate samples containing differently formulated products (dark, white and milk) have been tested: the former made of samples obtained under standard process conditions, the second including samples added with some volatile compounds associated to degradation processes and/or low quality raw materials to obtain artificially off-flavoured samples. Analysis with both gas sensor arrays resulted in a good discrimination between standard and artificially off flavoured chocolate samples. The best performance was obtained using the gold nanoparticles peptide sensors with over 90% of correctly assigned samples. (C) 2014 Elsevier B.V. All rights reserved