Hi everyone, recently while discussing we were searching for how to map the motorway junction tag, I found some examples where the tag was right when the continuous line starts, so the legal restriction of the do not cross line in Italy, one user argued that the physical separation is the king and so the tagging is right, while I argue that the node should be put before because that point isn’t the point where a car can legally turn smoothly, also another thing I was saying is that the relation between the separation of ways is that the physical separation implies two separated ways on OSM but two separated ways might not be separated by a physical barrier, but a visual or a difference in classification and purpose might make them separated.
I’ll send you the images and hope to hear your opinion
I’d say they’re both wrong because they’re starting arbitrarily where the no-lane-change line ends, not where the theoretical (painted) gore begins. Out of the two examples you provided
Consider the following:
placement=right_of:1 is in place on both motorways as only the left two lanes continue as through lanes past the end of the city in either direction. placement=transition is in effect on the ramp segment from the motorway_junction node to the physical gore (where the ramp physically becomes its own roadway; this is unusually long on the eastbound side due to the unusually huge theoretical gore).
Putting the intersection of the motorway and the ramp at the end of the theoretical gore helps ensure accuracy of prompts during navigation. Your examples would cause the directions for exiting the road to come up slightly to very early and potentially start moving on to prompts for the end of the ramp before you’ve even entered the ramp. And when entering, the confirmation prompt after merging would be slightly late.