Rethinking yes/no legal access tags on ways to document physical restrictions

Well, the wiki has a lot of catching up to do :wink: And yes, we obviously need to start somewhere. Access tags on ways are the most common (and often controversial) starting point.

Are there really any physical restrictions on gates or obstacles (like locked, width, height, or smoothness) that a router cannot interpret or that could influence a particular type of navigation? There was a separate discussion earlier, but I wanted to address the highways first.