543 research outputs found
Individual Adaption in a Path-Based Simulation of the Freeway Network of Northrhine-Westfalia
Traffic simulations are made more realistic by giving individual drivers
intentions, i.e. an idea of where they want to go. One possible implementation
of this idea is to give each driver an exact pre-computed path, that is, a
sequence of roads this driver wants to follow. This paper shows, in a realistic
road network, how repeated simulations can be used so that drivers can explore
different paths, and how macroscopic quantities such as locations of jams or
network throughput change as a result of this
Self-Organized Criticality and Noise in Traffic
Phantom traffic jams may emerge ``out of nowhere'' from small fluctuations
rather than being triggered by large, exceptional events. We show how phantom
jams arise in a model of single lane highway traffic, which mimics human
driving behavior. Surprisingly, the optimal state of highest efficiency, with
the largest throughput, is a critical state with traffic jams of all sizes. We
demonstrate that open systems self-organize to the most efficient state. In the
model we study, this critical state is a percolation transition for the phantom
traffic jams. At criticality, the individual jams have a complicated fractal
structure where cars follow an intermittent stop and go pattern. We
analytically derive the form of the corresponding power spectrum to be
with exactly. This theoretical prediction agrees
with our numerical simulations and with observations of noise in real
traffic.Comment: 13 pages, uuencoded with style file mprocl.sty. 6 Figures not
included but can be mailed on request. Will appear in ``Traffic and Granular
Flow,'' eds. D.E. Wolf, M. Schreckenberg, and A. Bachem (World Scientific,
Singapore, 1996.
The Influence of Multi-agent Cooperation on the Efficiency of Taxi Dispatching
The paper deals with the problem of the optimal collaboration scheme in taxi dispatching between customers, taxi drivers and the dispatcher. The authors propose three strategies that differ by the amount of information exchanged between agents and the intensity of cooperation between taxi drivers and the dispatcher. The strategies are evaluated by means of a microscopic multi-agent transport simulator (MATSim) coupled with a dynamic vehicle routing optimizer (DVRP Optimizer), which allows to realistically simulate dynamic taxi services as one of several different transport means, all embedded into a realistic environment. The evaluation is carried out on a scenario of the Polish city of Mielec. The results obtained prove that the cooperation between the dispatcher and taxi drivers is of the utmost importance, while the customer–dispatcher communication may be reduced to minimum and compensated by the use of more sophisticated dispatching strategies, thereby not affecting the quality of service
Agent-based modelling of air transport demand
Constraints such as opening hours or passenger capacities influence travel options that can be offered by an airport and by the connecting airlines. If infrastructure, policy or technological measures modify transport options, then the benefits do not only depend on the technology, but also on possibly heterogeneous user preferences such as desired arrival times or on the availability of alternative travel modes. This paper proposes an agent-based, iterative assignment procedure to model European air traffic and German passenger demand on a microscopic level, capturing individual passenger preferences. Air transport technology is simulated microscopically, i.e. each aircraft is represented as single unit with attached attributes such as departure time, flight duration or seat availability. Trip-chaining and delay propagation can be added. Microsimulation is used to verify and assess passengers’ choices of travel alternatives, where those choices improve over iterations until an agent-based stochastic user equilibrium is reached. This requires fast simulation models, thus, similar to other approaches in air traffic modelling a queue model is used. In contrast to those approaches, the queue model in this work is solved algorithmically. Overall, the approach is suited to analyze, forecast and evaluate the consequences of mid-distance transport measures
Modeling Location Choice of Secondary Activities with a Social Network of Cooperative Agents
Activity-based models in transportation science focus on the description of human trips and activities. Modeling the spatial decision for so-called secondary activities is addressed in this paper. Given both home and work locations, where do individuals perform activities such as shopping and leisure? Simulation of these decisions using random utility models requires a full enumeration of possible outcomes. For large data sets, it becomes computationally unfeasible because of the combinatorial complexity. To overcome that limitation, a model is proposed in which agents have limited, accurate information about a small subset of the overall spatial environment. Agents are interconnected by a social network through which they can exchange information. This approach has several advantages compared with the explicit simulation of a standard random utility model: (a) it computes plausible choice sets in reasonable computing times, (b) it can be extended easily to integrate further empirical evidence about travel behavior, and (c) it provides a useful framework to study the propagation of any newly available information. This paper emphasizes the computational efficiency of the approach for real-world examples
Parallel implementation of the TRANSIMS micro-simulation
This paper describes the parallel implementation of the TRANSIMS traffic
micro-simulation. The parallelization method is domain decomposition, which
means that each CPU of the parallel computer is responsible for a different
geographical area of the simulated region. We describe how information between
domains is exchanged, and how the transportation network graph is partitioned.
An adaptive scheme is used to optimize load balancing. We then demonstrate how
computing speeds of our parallel micro-simulations can be systematically
predicted once the scenario and the computer architecture are known. This makes
it possible, for example, to decide if a certain study is feasible with a
certain computing budget, and how to invest that budget. The main ingredients
of the prediction are knowledge about the parallel implementation of the
micro-simulation, knowledge about the characteristics of the partitioning of
the transportation network graph, and knowledge about the interaction of these
quantities with the computer system. In particular, we investigate the
differences between switched and non-switched topologies, and the effects of 10
Mbit, 100 Mbit, and Gbit Ethernet. keywords: Traffic simulation, parallel
computing, transportation planning, TRANSIM
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