I live in Cleveland, Ohio, but work in Akron, Ohio. If Summit county decided institute a policy that every person entering the county was subject to search, "for general public protection," it seems like your arguments would support such an arrangement.

When you really look at it, my working in Akron (or working at all) is "completely voluntary." Obviously the government (county in this case) is bound by the constitution, but the company responsible for maintaining the roads could do the searches, couldn't they?