Dutch traffic sign C1: https://commons.wikimedia.org/wiki/File:Nederlands_verkeersbord_C1_mb.svg

Essentially this on-ramp can be closed remotely by the traffic control centre via dynamic traffic sign displays (in case of an incident in the Corbulotunnel).

Not sure what the ideal tag for this is, but I figured something similar to maxspeed:variable makes sense: https://wiki.openstreetmap.org/wiki/Key:maxspeed:variable