Based on additional information provided by @aighes I just added analysis support for public-transport data of osm to ptna for
- US-MI-DDOT
- Detroit area (Dearborn, Detroit, Hamtramck, Highland Park), Michigan (bug in Overpass-Turbo)
- Detroit Department of Transportation (DDOT)
- CSV data in the OSM wiki has been prepared based on GTFS data: DDOT Routes
- analysis support for gtfs has also been added US-MI-DDOT