I was once hit on a roundabout by a guy who was trying to run straight through it without slowing down at all. My car was a write-off. As no witnesses came forward (even though it happened at rush hour) the police were not interested and said that it was "knock for knock". Apparently the other driver was not from this area and it wass the first time he had used this road. Obviously he was unfamiliar with the layout and maybe this contributed to the accident but it's a difficult thing to prove. As Eddie51 has already said, it's just one of those unfortunate things you have no choice but to accept even though it seems a little unjust.