My brother-in-law, John Tompkins, and I, worked at the Laurelton Drive-In on Hwy 88 in Brick, NJ back in the early '60's for two seasons. Our job was to go around the lot with big 5-cell flashlights when the movie was on and if we didn't see any heads above the top of the seat to tell the occupants that they had to sit up.
Hey, somebody had to do it!