195,621 research outputs found
Work domain analysis and intelligent transport systems: Implications for vehicle design
This article presents a Work Domain Analysis (WDA) of the road transport system in Victoria, Australia. A series of driver information requirements and tasks that could potentially be supported through the use of Intelligent Transport Systems (ITS) are then extracted from the WDA. The potential use of ITS technologies to circumvent these information gaps and provide additional support to drivers is discussed. It is concluded that driver information requirements are currently not entirely satisfied by contemporary vehicle design and also that there are a number of driving tasks that could be further supported through the provision of supplementary systems within vehicles
Cellular Automata Models of Road Traffic
In this paper, we give an elaborate and understandable review of traffic
cellular automata (TCA) models, which are a class of computationally efficient
microscopic traffic flow models. TCA models arise from the physics discipline
of statistical mechanics, having the goal of reproducing the correct
macroscopic behaviour based on a minimal description of microscopic
interactions. After giving an overview of cellular automata (CA) models, their
background and physical setup, we introduce the mathematical notations, show
how to perform measurements on a TCA model's lattice of cells, as well as how
to convert these quantities into real-world units and vice versa. The majority
of this paper then relays an extensive account of the behavioural aspects of
several TCA models encountered in literature. Already, several reviews of TCA
models exist, but none of them consider all the models exclusively from the
behavioural point of view. In this respect, our overview fills this void, as it
focusses on the behaviour of the TCA models, by means of time-space and
phase-space diagrams, and histograms showing the distributions of vehicles'
speeds, space, and time gaps. In the report, we subsequently give a concise
overview of TCA models that are employed in a multi-lane setting, and some of
the TCA models used to describe city traffic as a two-dimensional grid of
cells, or as a road network with explicitly modelled intersections. The final
part of the paper illustrates some of the more common analytical approximations
to single-cell TCA models.Comment: Accepted for publication in "Physics Reports". A version of this
paper with high-quality images can be found at: http://phdsven.dyns.cx (go to
"Papers written"
Offline reconstruction of missing vehicle trajectory data from 3D LIDAR
LIDAR has become an important part of many autonomous vehicles with its
advantages on distance measurement and obstacle detection. LIDAR produces point
clouds which have important information about surrounding environment. In this
paper, we collected trajectory data on a two lane urban road using a Velodyne
VLP-16 Lidar. Due to dynamic nature of data collection and limited range of the
sensor, some of these trajectories have missing points or gaps. In this paper,
we propose a novel method for recovery of missing vehicle trajectory data
points using microscopic traffic flow models. While short gaps (less than 5
seconds) can be recovered with simple linear regression, and longer gaps are
recovered with the proposed method that makes use of car following models
calibrated by assigning weights to known points based on proximity to the gaps.
Newell's, Pipes, IDM and Gipps' car following models are calibrated and tested
with the ground truth trajectory data from LIDAR and NGSIM I-80 dataset. Gipps'
calibrated model yielded the best result
A Cellular Automaton Model for the Traffic Flow in Bogota
In this work we propose a car cellular automaton model that reproduces the
experimental behavior of traffic flows in Bogot\'a. Our model includes three
elements: hysteresis between the acceleration and brake gaps, a delay time in
the acceleration, and an instantaneous brake. The parameters of our model were
obtained from direct measurements inside a car on motorways in Bogot\'a. Next,
we simulated with this model the flux-density fundamental diagram for a
single-lane traffic road and compared it with experimental data. Our
simulations are in very good agreement with the experimental measurements, not
just in the shape of the fundamental diagram, but also in the numerical values
for both the road capacity and the density of maximal flux. Our model
reproduces, too, the qualitative behavior of shock waves. In addition, our work
identifies the periodic boundary conditions as the source of false peaks in the
fundamental diagram, when short roads are simulated, that have been also found
in previous works. The phase transition between free and congested traffic is
also investigated by computing both the relaxation time and the order
parameter. Our work shows how different the traffic behavior from one city to
another can be, and how important is to determine the model parameters for each
city.Comment: 14 pages and 13 figures (gzipped tar file). Submitted to
Int.J.Mod.Phys.C. Minor changes, specially at references and typoes, plus a
clearer summary of the CA rule
Deterministic Models for Traffic Jams
We study several deterministic one-dimensional traffic models. For integer
positions and velocities we find the typical high and low density phases
separated by a simple transition. If positions and velocities are continuous
variables the model shows self-organized criticality driven by the slowest car.Comment: 11 pages, latex, HLRZ preprint 46/93, UKAM-WP 93.13
Learning from 20 Years of Payments for Ecosystem Services in Costa Rica
Costa Rica's Payments for Ecosystems Services (PES) programme has become something of an icon in the world of conservation. Its innovative blend of economic and regulatory instruments - and its hitches and successes - provide a valuable source of inspiration for other countries that are looking for effective ways to conserve and regenerate ecosystems. Since 1997, nearly one million hectares of forest in Costa Rica have been part of the PES programme at one time or another, and forest cover has now returned to over 50 per cent of the country's land area, from a low of just 20 per cent in the 1980s. What lessons can be learnt from the 20 years since it was founded? Also published in Spanish, this paper is for local practitioners, international researchers and donors who are interested in the Costa Rican experience
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