(17 Apr 2016, 5:22 pm)Dan wrote Surely the system is in place to alert drivers to take caution, rather than to take evasive action to avoid a low bridge which isn't even on the route of that service..?

I would anticipate that drivers are informed of the various systems which are in place on buses in the training process or the mentoring process.

Surely if the bus fits, it will always fit; so no need no take caution? I'm not aware of any bridges that shrink or buses that suddenly grow taller. 

I'm not sold on this system being a good thing. either the noise from the false alarms becomes distraction or the opposite where the drivers hear it so much they begin not to take notice; even when the alarm would be useful.