The roads are planned but as of yet unbuilt......Road planning and construction takes Time and Money...........
Cartographers (map makers) have the latest information available from planning boards....land use.......since a map is destined to be around for a long time they want to include the most information as possible....Even future projects.......Usually they try to indicate unfinished projects with a lighter/broken line..........
Economics determines When-and-What gets built........unfortunately many roads only exist on maps.......
I find it rare for existing Public streets to be "closed off"......unless there's a secret adgenda back behind the fence ?Hmmmmmm