[Tagging] Clashing access tags

[Richard Fairhurst]

Hi all,

Occasionally I encounter tag combinations like this:

	bicycle=designated
	highway=proposed

	(from https://www.openstreetmap.org/way/335831004)

where the "bikes can ride along here" of the first tag is contradicted 
by the "this hasn't even been built yet" of the second.

Similarly, on occasion I've found ways which are tagged access=no 
("nothing is allowed along here") but are part of a bike route relation 
("bikes can ride along here").

To some degree they're similar to "trolltags" 
(https://wiki.openstreetmap.org/wiki/Trolltag) - where the meaning of 
one tag is "radically changed" by another.

Two questions:

1. Is there any precedent for how to parse these contradictory tags? At 
present cycle.travel will assume the most optimistic outcome, which is 
good for a cycle route which goes over a private road and the mapper has 
forgotten to add bicycle=permissive, but not good for a new cycleway 
which hasn't yet been constructed.

2. Can we get warnings about this into validators etc.? I note iD 
doesn't warn about it. (No idea what JOSM does.)

cheers
Richard