336 research outputs found
Public transit route planning through lightweight linked data interfaces
While some public transit data publishers only provide a data dump – which only few reusers can afford to integrate within their applications – others provide a use case limiting origin-destination route planning api. The Linked Connections framework instead introduces a hypermedia api, over which the extendable base route planning algorithm “Connections Scan Algorithm” can be implemented. We compare the cpu usage and query execution time of a traditional server-side route planner with the cpu time and query execution time of a Linked Connections interface by evaluating query mixes with increasing load. We found that, at the expense of a higher bandwidth consumption, more queries can be answered using the same hardware with the Linked Connections server interface than with an origin-destination api, thanks to an average cache hit rate of 78%. The findings from this research show a cost-efficient way of publishing transport data that can bring federated public transit route planning at the fingertips of anyone
Trip-Based Public Transit Routing
We study the problem of computing all Pareto-optimal journeys in a public
transit network regarding the two criteria of arrival time and number of
transfers taken. We take a novel approach, focusing on trips and transfers
between them, allowing fine-grained modeling. Our experiments on the
metropolitan network of London show that the algorithm computes full 24-hour
profiles in 70 ms after a preprocessing phase of 30 s, allowing fast queries in
dynamic scenarios.Comment: Minor corrections, no substantial changes. To be presented at ESA
201
Trip-Based Public Transit Routing Using Condensed Search Trees
We study the problem of planning Pareto-optimal journeys in public transit
networks. Most existing algorithms and speed-up techniques work by computing
subjourneys to intermediary stops until the destination is reached. In
contrast, the trip-based model focuses on trips and transfers between them,
constructing journeys as a sequence of trips. In this paper, we develop a
speed-up technique for this model inspired by principles behind existing
state-of-the-art speed-up techniques, Transfer Pattern and Hub Labelling. The
resulting algorithm allows us to compute Pareto-optimal (with respect to
arrival time and number of transfers) 24-hour profiles on very large real-world
networks in less than half a millisecond. Compared to the current state of the
art for bicriteria queries on public transit networks, this is up to two orders
of magnitude faster, while increasing preprocessing overhead by at most one
order of magnitude
General scores for accessibility and inequality measures in urban areas
In the last decades, the acceleration of urban growth has led to an
unprecedented level of urban interactions and interdependence. This situation
calls for a significant effort among the scientific community to come up with
engaging and meaningful visualizations and accessible scenario simulation
engines. The present paper gives a contribution in this direction by providing
general methods to evaluate accessibility in cities based on public
transportation data. Through the notion of isochrones, the accessibility
quantities proposed measure the performance of transport systems at connecting
places and people in urban systems. Then we introduce scores rank cities
according to their overall accessibility. We highlight significant inequalities
in the distribution of these measures across the population, which are found to
be strikingly similar across various urban environments. Our results are
released through the interactive platform: www.citychrone.org, aimed at
providing the community at large with a useful tool for awareness and
decision-making
Route Planning in Transportation Networks
We survey recent advances in algorithms for route planning in transportation
networks. For road networks, we show that one can compute driving directions in
milliseconds or less even at continental scale. A variety of techniques provide
different trade-offs between preprocessing effort, space requirements, and
query time. Some algorithms can answer queries in a fraction of a microsecond,
while others can deal efficiently with real-time traffic. Journey planning on
public transportation systems, although conceptually similar, is a
significantly harder problem due to its inherent time-dependent and
multicriteria nature. Although exact algorithms are fast enough for interactive
queries on metropolitan transit systems, dealing with continent-sized instances
requires simplifications or heavy preprocessing. The multimodal route planning
problem, which seeks journeys combining schedule-based transportation (buses,
trains) with unrestricted modes (walking, driving), is even harder, relying on
approximate solutions even for metropolitan inputs.Comment: This is an updated version of the technical report MSR-TR-2014-4,
previously published by Microsoft Research. This work was mostly done while
the authors Daniel Delling, Andrew Goldberg, and Renato F. Werneck were at
Microsoft Research Silicon Valle
Transfer Customization with the Trip-Based Public Transit Routing Algorithm
In the context of routing in public transit networks, we consider the issue of the customization of walking transfer times, which is incompatible with the preprocessing required by many state-of-the-art algorithms. We propose to extend one of those, the Trip-Based Public Transit Routing algorithm, to take into account at query time user defined transfer speed and maximum transfer duration. The obtained algorithm is optimal for the bicriteria problem of optimizing minimum arrival time and number of transfers. It is tested on two large data sets and the query times are compatible with real-time queries in a production context
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