This is fascinating: an instructional video from 1988 for British Royal Military Police personnel to watch before travelling the 103 miles of autobahn across East Germany to West Berlin. (A Cold War refresher: West Berlin was completely surrounded by East Germany — the city was not on the border.) Those in transit had to follow many rules:
Approach the Soviet sentry who will be standing close to the small hut on the left of the road. He will salute you. You must, irrespective of your sex, status, or form of dress, return his salute.
They also couldn’t stop anywhere but a few designated areas, could only deal with Soviet personnel (and not East German personnel), were forbidden from speaking Russian, and obviously couldn’t take photos. What a time capsule!