I had an office along the freeway route between downtown Detroit and our local air base, where the presidents typically flew in. I saw a couple presidents that way (42 & 43).

The freeway in the motorcade's direction was always closed to traffic. Police cars would be positioned on all the overpasses. Downtown, they would arrange for semi-style dump trucks to pull into place to block streets and overpasses so no one could get above the motorcade from the roadway.