[mkgmap-dev] Ideas: dead-end-check=3, redundant or impossible turn restrictions

Fri Dec 11 05:05:57 GMT 2009

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