It has happened to G in his pickup truck when some twonk tried to cut in front of him into a gap far too small to fit. Once it does happen it is difficult to know what to do for the best. When G did brake the other car suddenly regained traction and spun off across all three lanes which could have been awful, but fortunately nothing else was in the way. So other than one very sheepish twonk (who once he had calmed down asked us to please not tell his wife what he'd done!) no harm was done. The bits of subaru wiped off the truck so there was only minor paintwork damage that he paid for. His car came off less well though.