7,337 research outputs found
Self-Control of Traffic Lights and Vehicle Flows in Urban Road Networks
Based on fluid-dynamic and many-particle (car-following) simulations of
traffic flows in (urban) networks, we study the problem of coordinating
incompatible traffic flows at intersections. Inspired by the observation of
self-organized oscillations of pedestrian flows at bottlenecks [D. Helbing and
P. Moln\'ar, Phys. Eev. E 51 (1995) 4282--4286], we propose a self-organization
approach to traffic light control. The problem can be treated as multi-agent
problem with interactions between vehicles and traffic lights. Specifically,
our approach assumes a priority-based control of traffic lights by the vehicle
flows themselves, taking into account short-sighted anticipation of vehicle
flows and platoons. The considered local interactions lead to emergent
coordination patterns such as ``green waves'' and achieve an efficient,
decentralized traffic light control. While the proposed self-control adapts
flexibly to local flow conditions and often leads to non-cyclical switching
patterns with changing service sequences of different traffic flows, an almost
periodic service may evolve under certain conditions and suggests the existence
of a spontaneous synchronization of traffic lights despite the varying delays
due to variable vehicle queues and travel times. The self-organized traffic
light control is based on an optimization and a stabilization rule, each of
which performs poorly at high utilizations of the road network, while their
proper combination reaches a superior performance. The result is a considerable
reduction not only in the average travel times, but also of their variation.
Similar control approaches could be applied to the coordination of logistic and
production processes
Operation Regimes and Slower-is-Faster-Effect in the Control of Traffic Intersections
The efficiency of traffic flows in urban areas is known to crucially depend
on signal operation. Here, elements of signal control are discussed, based on
the minimization of overall travel times or vehicle queues. Interestingly, we
find different operation regimes, some of which involve a "slower-is-faster
effect", where a delayed switching reduces the average travel times. These
operation regimes characterize different ways of organizing traffic flows in
urban road networks. Besides the optimize-one-phase approach, we discuss the
procedure and advantages of optimizing multiple phases as well. To improve the
service of vehicle platoons and support the self-organization of "green waves",
it is proposed to consider the price of stopping newly arriving vehicles.Comment: For related work see http://www.helbing.or
SymbioCity: Smart Cities for Smarter Networks
The "Smart City" (SC) concept revolves around the idea of embodying
cutting-edge ICT solutions in the very fabric of future cities, in order to
offer new and better services to citizens while lowering the city management
costs, both in monetary, social, and environmental terms. In this framework,
communication technologies are perceived as subservient to the SC services,
providing the means to collect and process the data needed to make the services
function. In this paper, we propose a new vision in which technology and SC
services are designed to take advantage of each other in a symbiotic manner.
According to this new paradigm, which we call "SymbioCity", SC services can
indeed be exploited to improve the performance of the same communication
systems that provide them with data. Suggestive examples of this symbiotic
ecosystem are discussed in the paper. The dissertation is then substantiated in
a proof-of-concept case study, where we show how the traffic monitoring service
provided by the London Smart City initiative can be used to predict the density
of users in a certain zone and optimize the cellular service in that area.Comment: 14 pages, submitted for publication to ETT Transactions on Emerging
Telecommunications Technologie
Derivation of a Fundamental Diagram for Urban Traffic Flow
Despite the importance of urban traffic flows, there are only a few
theoretical approaches to determine fundamental relationships between
macroscopic traffic variables such as the traffic density, the utilization, the
average velocity, and the travel time. In the past, empirical measurements have
primarily been described by fit curves. Here, we derive expected fundamental
relationships from a model of traffic flows at intersections, which suggest
that the recently measured fundamental diagrams for urban flows can be
systematically understood. In particular, this allows one to derive the average
travel time and the average vehicle speed as a function of the utilization
and/or the average number of delayed vehicles.Comment: For related work, see http://www.helbing.or
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