A glitch in the system has caused some Metro Trains to turn on a new safety message telling commuters to "mind the gap".

And its frequency is driving some commuters crazy.

Infrastructure Australia says Metro Trains' franchise agreement with the Victorian government has been a success. Credit:Craig Abraham

The message, alerting travellers to the gap between the train and the platform, is not normally heard in Metro trains.

But a programming error has caused the announcement to be played on some trains as they enter and exit a station.