Phone number international format in GTFS about transit HOT 2 OPEN

A side note, we should not be including non-backwards compatible options as possible solutions, since non-backwards compatibility is inherently a nonstarter.

from transit.

I have always understood from Google Maps implementation that the URI "tel:" must work. While this is not explicitly mentioned under agency_phone, my suggestion would be not to make it human readible or E.164 but perferably: RFC3966.

Original text:
"A voice telephone number for the specified agency. This field is a string value that presents the telephone number as typical for the agency's service area. It may contain punctuation marks to group the digits of the number. Dialable text (for example, TriMet's "503-238-RIDE") is permitted, but the field must not contain any other descriptive text."

from transit.