OpenStreetMap
I exposed a couple of junctions I'd made in Delaware to scrutiny and got "gee, borders on vandalism", "I would revert on sight", "love the detail" and "looks ok, but maybe overly complicated" types of responses. My argument about detail mapping of US highway junctions is that markings on the pavement have the force of law in some states (including Delaware) and, therefore, are valid for interpretation through restriction-type relations. The difficulty comes in the actual junction site and the many way-crossings which result from interpretation of pavement markings as legally-enforceable restrictions. --ceyockey
Comment from Vclaw on 5 February 2012 at 13:59
The consensus in OSM is only to map roads as separate ways if they are physically separated. If it is just a white painted line, then they are not physically separate (even if it is illegal to drive across the line).
Comment from ceyockey on 6 February 2012 at 13:24
Yes, well, that does seem to be the consensus, though you are the first to articulate sufficiently clearly to give it the force of a business rule.