[bigiain]

As you say, it depends on the jurisdiction.

Here (Australia) the rules define "road related areas" as including private property that does not have a "normally locked gate" protecting access.

This means all road rules (including stop signs, alcohol/drug rules, mobile phone use, and speed limits) apply in places like publicly accessible carparks on private property, and homeowner's driveways if they do not have a "normally locked gate". People have been booked for drink driving and mobile phone use sitting in their cars in their own driveways here (almost certainly after "failing the attitude test" and pissing a cop off enough for them to punitively enforce a stupid interpretation of a poorly written law, but that's a different rant...)