Turn:lanes=slight_left/right versus merge_to_left/right

A mapper in the region has been applying connectivity relations and turn:lanes tags onto motorway, trunk and primary roads in large numbers. Large numbers are also flagged by QA, particularly Osmose (just inhale and exhale slowly please). The central issue is in all of the flagged points is that AFA turn:lanes are concerned which are mapped to seemingly none existing lanes and or lanes are tagged as were they a continuance, my interpretation, opposed to a lane that ends.

Trying to understand the meaning of one not seen before in data is slight_left and slight_right flagged in every place seen where used here. In the instance a parallel ramp-on was changed from 2 + 1 lane ways with a joint to a single 3 lane road eventually changing to 2 lanes or for that matter 2 lane road changing to 1 (main plus ramp on).

The turn:lanes value given in the example is through|through|slight_left. Looking at the wiki on turn:lanes in past I would have given the merge_to_left instead (see pic below) of the Ortona motorway junction. Slight_left to me is just saying the lane you’re following is bending slightly to the left, not ending, where merge tells the lane you’re in is ending, move over to the left in places called in free translation ‘zip’ while adapting your speed to the lane you’re changing over to without causing slowing on the main route.

Notably there’s no direction arrows on the deck, only solid and dashed lining as dividers to indicate where changing allowed or not.

Comments please, slight_left or merge_to_left?

(I’ll write up a separate post on the many connectivity relations being flagged at junctions, not seen in the larger region until now)

In this case, narrow down the 3 lanes to 2: it is merge_to_* (“left” in right-driving countries)

In the case where a lane separates from 3 lanes (just to leave the motorway) it can be slight_* (“right” in right-driving countries)

1 Like

After a dozen plus correcting, the message on the connectivity sunk in as it says 'Bad lanes number OR ‘turn:lanes’ these being intertwined in QA checking. At least when it says on same connectivity=1:1|2:2|3:2 it seems to indicate correctly that those in lane 3 need to continue their way in lane 2. (though there are pelotons who can’t wait to hit the peddle in 1:1 since I only see a dash line divider between 1 and 2 as much as observing in traffic it might even be desirable for those nearing the merge lane on main to switch to 1, if that can be safely done, to make a merge easier… keep your lane, not here ;O)

Edit: After spending last 5 hours tracking each one down of the through|through|slight_left entries along the A14 and part of the A24/25, all without fail had to be changed to merge_to_left and fixing other stuff on the go like many wiki repeats on each motorway cut of a 2000 member road route and removing odd ditties like track tags when I’m reasonably sure agricultural vehicles are not permitted, minspeed 40. TurboOverpass tells there’s 247 left worldwide, the bulk in my region and all by the same hand. At least in right hand drive Europe they need review as the probability of this combo being real is unlikely. Anyway, this is the regional and global picture on possible misdirection. Dots come in pairs where 2,3,4 road sections need their turn:lanes corrected, by hand as I’d loath to cause mangle while correcting in mechanical fashion.

To check and (possibly) correct:
Local region

Global, where the left hand side driving countries could be correct

And this is only for 3 lane to 2 lane changes. Did a few on 2 to 1 that popped up not much here that goes over 3 lanes.


Having worked through about 75% of the suspects in Lazio/Abruzzo, all guilty as charged and a few more added that were forgotten, happy to note that most all alerts on the connectivity relations vanished by themselves i.e. it was validation cross talk. Some were broken where a ‘to’ or ‘from’ was missing. There’s a nagger though… in trying to understand these, what routes to lanes N:0 ? Saw a few in passing but forgot to note where. When there’s a simple motorway change from 3 lanes to 2 I’d be inclined to add a 1:1|2:2|3:2 on the transit section, but it’s really not my thing to get more than tangentially involved in tagging these. For now just ‘correct’ if I know how to and move on.