How can Transit app vibrate my phone even with notification sounds turned off?
When Transit App is in Go mode, it can deliver notifications using the Turn-by-turn API which has some special privileges.


Vibration is possible if Notifications are turned on for Transit App, even if all the specific options are turned off. Disabling notifications for the app prevents vibration.
Audible announcement of upcoming stops is permitted even if notifications are entirely disabled for Transit App. But of course audible announcements will only play if enabled in Transit App by toggling the sound icon in Go mode.


These special notifications also seem to bypass Do Not Disturb mode.