It is obviously important that you can be sure the doors are properly closed before setting off. I have had a door swing open on a roundabout in the past. So now, every time I close the door, I try the internal locking lever. If it will go all the way around the quadrant, the door is properly closed on the second click, but if it will only go halfway, then the door is only holding on the first click and is liable to spring open under pressure or flexing. A simple but effective habit to get into and it could save a life!
