I didn't go so far as to say that building the roads gives the government plenary power over those who drive upon them, but I do believe the government is free to set reasonable conditions for their use. For instance, drivers must be somehow qualified as through a course or an exam leading to licensure. The expectation that one would operate a large and deadly machine while not impaired seems likewise reasonable. My rationale supports government making driving under the influence illegal and punishable. I would not go so far as to say government should have a blank check to search and seize, as with a road block sobriety test. I think that is too much. But is it acceptable to have highway officers on the alert for poor driving that may indicate inebriation? I would think the answer to that question is yes.