Thanks for the great meeting during TRB. It was very interesting to learn what you are doing with GTFS.
I'm working on developing a proposal for the EU's new Horizon 2020 research program that would use open data to support sustainable transport. Very quickly the idea is to have several cities create consistent API feeds with data on sustainable transport modes (biking, walking, public transport), implement several programs to encourage independent developers to create apps using this data, and share best practices via two international conferences and research reports.
In the sense of this group the idea is to "develop" a "GTFS" for sustainable transport modes, and encourage cities to release data in consistent formats (e.g. Vienna does not provide public transport schedule data in GTFS).
Let me know if you have ideas or might be interested in participating in the project.