[Tagging] access forbidden for tourist busses

[M∡rtin Koppenhoefer]

Recently I found this sign which I interpret as "access forbidden to
touristic busses":

http://www.23hq.com/dieterdreist/photo/6610385

It is at a driveway to the local cemetery, near a very popular
monument (unesco world heritage). Do we have to invent another access
tag, or is there already something in use?

My first idea was "tourist_bus=no"

cheers,
Martin