This code list is used in association with the Tunnel attribute which is present within the Transport Link Feature Type. On Transport Links that represent a road feature, it indicates whether there is a presence of a Tunnel, e.g 'yes' or Null.
yes
Indication that there is a tunnel
building_passage
A tunnel passage that goes through/under a building, but is not inside the building itself.
canal
Tunnel for navigable canals
culvert
For a stream/drain/ditch passing under a road. Use it on the section of waterway passing under the road.
flooded
A long (>100 m) tunnel where flowing water or other fluid prevent humans from safely walking inside