If possible, make a U-turn!
I have recently returned from being on holiday in the south of England, a part of the country that is unfamiliar to me.
Every day I found myself having to rely on my satnav to prevent me from getting lost and bring me to my destination. But even then I still managed to take a few wrong turnings and received the instruction from the satnav: ‘If possible, make a U-turn’. Needless to say, it was not always possible and the satnav simply had to recalculate the route.