Nudging is a door control mode that closes the doors slowly with an audible warning after they have been held open beyond a set time, typically 20 to 30 seconds. It is used when a passenger blocks the doors or an obstruction keeps the safety edge active, so that one car cannot immobilise a whole group. During nudging the closing force is limited to 150 newtons and the light curtain is bypassed, which is why the audible signal is mandatory. Normal operation resumes once the doors close.