TFl has the data and City Mapper use a lot of it but with their own additional heuristics. Anyone can write an app that consumes the data. https://api.tfl.gov.

TFl has the data and City Mapper use a lot of it but with their own additional heuristics. Anyone can write an app that consumes the data. https://api.tfl.gov.uk/ https://api.tfl.gov.uk/