One of my colleagues and I have completed a report on developing multimodal trip planners. The report focuses on open-source software, and open data sources such as OpenStreetMap and public transportation data in GTFS format. The report is available at
I've added this to the list of research reports on the OSM wiki research page, and a note on the wiki OpenTripPlanner page, with links to the report.
Discussions that we followed, and in some cases participated in, on the OSM talk, talk-us, talk-ca, and talk-transit listservs were very helpful to the project.
We are following up the project with several proposals to improve documentation and support a local organization in moving beyond this feasibility study to full implementation. Our center is grant-funded, so although we will continue to follow progress in our spare time, significant follow-up work will depend on our ability to get proposals funded.
Please feel free to contact me if you have any questions about the project or report.