The city of West Orange New Jersey has been using text alerts for a while as an alert system for their transit system. They let transit users know ‘Text “wojitney” to 662-200-4303 to receive updates on the West Orange Jitney Transit System!’.
They then send out updates such as “ALERT: Route 2 experiencing mechanical difficulties. Other routes assisting in pickup and transport of riders this morning.” to those who are subscribed.
This is just one example of a city that has successfully used text alerts for transit system.