How does the Google Maps Directions API differentiate interline transfers?

Question

I am building an android transit app for real-time bus/train arrivals, I would also like to add directions for users using the google maps directions API.

My transportation agency (TriMet) uses interline / thru-route transfers. Interline transfers are transfers where the vehicle (bus, rail, etc) changes routes with passengers on board. Google Maps shows such transfers as:

My question: how does the google maps direction API implement interline transfers i.e. how do I know when the transfer is an interline transfer? Thanks.

Answer 1

Xomena is totally right in his comment: you need Google Transit API Static Transit, but you are right too: its not easy to get desired data from it.

Anyway, you can use some "dirty" workaround: make Google Maps Directions API request like

https://maps.googleapis.com/maps/api/directions/json?origin=Milwaukie/Main+St+MAX+Station,+Portland,+OR,+us&destination=Pioneer+Courthouse,+Portland,+OR,+us&mode=transit

get JSON response and analyze it: if route has several steps and

• there is no WALKING (and/or other) step between TRANSIT step[i] and step[i+1];

• end_location lat, lng and name tags of step[i] equals to start_location lat, lng and name of step[i+1];

• arrival_time tag of step[i] is around (1-2 minutes differs with) departure_time tag of step[i+1];

• line -> agencies -> name (and others, like phone) tag of step[i] equals to corresponding tags of step[i+1];

• line -> vehicle -> name& type for step[i] equals to corresponding tags step[i+1];

• may be something others attributes equals (or approximately equals for time) for step[i] and step[i+1];

its highly likely that there is interline transfer between step[i] and step[i+1] on Google Maps Directions API route.