When arriving at destination on diesel (say penzance) driver will put the train into turnaround mode. On a 9 car this will shut down all but 2 engines, and on a 5 car it will shut down all but 1 engine. This is to prevent noise and wasted fuel. 5 minutes before departure , driver should then switch on all engines again, but as there is no indication in the cab when train is in turnaround mode, it has been missed by some drivers and they have tried to pull away on one engine. This can be quickly rectified on the move by restarting all engines as soon as he realises his error, however in some cases the computer says no and engines need to be tripped out and reset causing delays.