The car park where I work, which isn’t open to the public, has signs and road markings exactly as you would find them on a public road. At the end of a shift people leave by the shortest possible route, totally ignoring these signs. Are the signs legal, and could we pursue an insurance claim even though it’s private land?
Some car parks are now classified as the public highway if the access is open, but otherwise the police couldn’t take action against anyone ignoring a traffic sign in a privately-owned car park. As far as insurance claims are concerned however you have to prove fault, so anyone who drove into you after ignoring a “Stop” sign even in a private car park wouldn’t have much of a defence.