Computing Isochrones in Multi-Modal, Schedule-Based Public Transport Networks

Modern decision support systems in the area of public transport networks often amount to reachability problems, where time tables and itineraries are influential factors. Isochrones are a recommended solution to these questions.
Isochrones are defined as the set of all points reachable from a specific point of interest given an equal time span. This paper describes the realization of a service oriented architecture component (i.e. service) that computes isochrones in multi-modal, schedule-based public transport networks.
The web service supports the well-known interface standards Web Feature Service (WFS) and Web Processing Service (WPS) by the Open Geospatial Consortium, Inc. (OGC), an international standards organization that is leading the development of standards for geospatial information.
The presented algorithm computes contemporary and exact isochrones based on the underlying time table data of the official Swiss public transport network, covering the 2010 / 2011 period. Given an arbitrary starting coordinate, a departure time and the latest possible arrival time, the service computes all potential shortest routes, such that a combination of walking and public transport are within the time limit. The resulting isochrones can be demonstrated using a visualization component, like Quantum GIS or a web browser that supports the Google Maps API. The web service has been successfully tested with Quantum GIS. Further development includes integration into a website for public use, performance improvement in the area of algorithm design, parallelisation, caching and the use of a graph database. For more information, please visit our website at http://cipt.ecomb.ch.