The blue UK sign "Cyclists Dismount" clearly misleads many people who believe it requires cyclists to dismount.  It is  significant problem when it leads to wrong info being added to OSM.

The legislative meaning of the blue "Cyclists Dismount" sign is this. It is an advisory sign, that for a short section ahead the path may prove impossible to ride on due to (1) Load head height (2) restricted width (3) restricted visibility. Case Law confirms it can be used for only these reasons (eg not a Cattle Grid, or path next to cliff). It needs repeating this is advice, and not a prohibition.

But, the sign may also be used to emphasise two locations where cycling is prohibited (1) Pedestrian Crossing (2) entrance to Pedestrian area.

So the sign I can see on Google StreetView is unlawfully placed.

I believe that the the signed "No Cycling" is the main access consideration. It goes beyond the common bicycle=no because it informs an offence is committed. 

Therefore it's important we map this a bicycle=no

Sustrans creating routes along ways that cannot be ridden is a bit of a joke. 

Don't know area, so leave it up to local mappers to make the decision.