I know there are many conditions (grey areas) under which the system will not work, plenty of information in the manual.
I had a bit of a "situation" last week. Parking the car in the NCP multi-storey place, pulling up to the ticket machine, yellow barrier ahead of me. All of a sudden car stops, honks and displays a message about the emergency breaking.
Bit weird, wasn't going quickly or unable to stop in time. Felt like the engine stalled, honk was a funny accent too.
This is what to expect when the system actually does work...... hope this helps in the slightest.