Posted by malenki on 23 February 2014 in German (Deutsch)

Out of curiosity I had a look for maxspeed= with values that contain at least one semicolon on taginfo.
It is most likely that this kind of maxspeed values are created by merging at least two highway segments with different maxspeed values.
If you want to have a look yourself click here and type a ";" in the (lower) search box for values.
Accumulating the numbers there are 1058 key-value-pairs containing a semicolon.
Interpolating this one can consider that supposedly at least 2116 highway segments got merged without the mapper taking good care about what he did. Looking at the topic it seems obvious that often more then two segments got united.

Now you could do the same check for cycleways, sidewalks, oneways and other keys which don't come to my mind at the moment.

I do not know of any Quality Assurance tool which is checking for this kind of errors. If you do, please mention it at the comments.
More important than to fix this data is not to create new errors of this kind.

  • Luckily the default behaviour for merging ways in JOSM has been altered from combining the values as "value1;value2" by default. Now the user is forced to select one of the conflicting values.
  • In Potlatch2 combined values are shown in red with a warning sign.
  • iD merges ways with conflicting tags without complaining. Of course there are no plans for an intrusive warning because "they run counter to iD's goal of encouraging new users to contribute to the map because they make them feel insecure, even when their edits are perfectly legitimate"(link). Another issue against iD regarding conflicting tags is a year old.

Comment from poppei82 on 23 February 2014 at 14:36

"I do not know of any Quality Assurance tool which is checking for this kind of errors."

Du kannst es gerne hier vorschlagen:

Comment from malenki on 23 February 2014 at 15:15

Thanks for the hint.
I wasn't aware that keepright is on github – the fact isn't mentioned on I mailed the author already but also will open an issue now:

Comment from poppei82 on 23 February 2014 at 19:21

No problem. Keepright has new maintainers. The github-version will be online soon. Thanks for the issue. I hopr that someone will implement this in upcoming keepright versions.

Comment from stw1701 on 25 February 2014 at 20:17

Other keys which are often or sometimes merged: name, landuse, tracktype, layer, width, wheelchair, lanes, smoothness, access (motor_vehicle, bicycle, ...), postal_code, trail_visibility, cycleway.

Thanks for the list of editors. I've seen such values for a long time now, but I've never found out which editor was to blame.

Comment from malenki on 25 February 2014 at 21:14

Please remember that the change in JOSM is quite recent. Before the default behaviour was also combining the tags.
Also it isn't said that every Potlatch user uses the expert mode. :)

I added your keys to the github issue mentioned above. I skipped name, access and cycleway since for the first two could (imo) quite some false positives show up (haven't checked the data about this); cycleway I had already listed.

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