While looking for accessible transportation data sets, it would be better to look for associated data sets for other needs and services. Are you aware of any such efforts?
Official dataset for data.gov http://www.data.gov/
A search example as a possible model: "traffic detectors" http://catalog.data.gov/dataset/traffic-detectors
HealthData.gov http://www.healthdata.gov/ if we want to try to locate those in need.
DataAPI for HealthData.gov... more »
Where the biggest gaps in data availability to support navigation and wayfinding applications (both indoor and outdoor) for persons with disabilities? Would it be possible and efficient to use crowdsourcing as a method to build up the required mapping and accessibility data? How might this work? (Persons with disabilities may include those with challenges in vision, hearing, mobility, and cognition.)