I got two more validation ideas, now that mkgmap is not complaining
about roundabouts, oneways or turn restrictions in finland.osm.bz2.
Both should be easy to implement.
Dead end check 3: Check dead ends in bidirectional streets.
Consider the following situation where AB joins the oneway street CB:
A============B<----------C
Normally, this is legitimate. However, if there is a turn restriction
(via=B, from=AB) that prevents the U-turn ABA, AB would be a dead end.
Another idea: complain about redundant or impossible turn restrictions.
A restriction whose "from" or "to" role is against the direction of a
oneway, is impossible. For example, only_straight_on (from=AB, via=B, to=CB).
An impossible restriction may also be redundant, meaning that it does not
restrict anything: no_u_turn (from=CB, via=B, to=CB). If there are no
other ways joining at B, the following would be redundant:
only_straight_on (from=CB, via=B, to=BA).
I came across some of these situations in a crossing in Vaasa. There were
other oneway errors in the area, but these I had to notice myself.
JOSM Validator did not complain.
Best regards,
Marko
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