Jarek 🚲
I don't think we have a tag specifically for "cars driven by people who then go on to cycle on the nearby trail". access=customers is the closest thing I'm coming up with - it's "customers" of the trail...

This seems this similar to a "trailhead parking" but I can't find a recommended tag for that either. (There is a highway=trailhead but that's for the trailhead point, not its parking. Logically related https://wiki.openstreetmap.org/wiki/Hiking lists amenity=parking but no further specific tags for it)

In practical terms, how would this even be enforced?