An interesting point was brought up in a Facebook thread by someone who felt confident they had a grasp of drone regulations in which they mentioned that they felt that the "right of way" by a highway was considered to be a part of the highway, and so flying above the right away when cars were driving by was equivalent to flying directly over cars, which is of course a no-no. I can't see to find any real information about what constitutes flying "above" vehicles with people in them or above people -- my common sense approach would be to assume that they mean "anything where there is a significant likelihood the drone would crash into the vehicles or people in the event of an unexpected mechanical failure", but maybe the FAA has it spelled out better somewhere. In my mind, hovering 200 feet up 50 feet to the south of the southernmost lane of an east-west highway is far enough away where you are no longer hovering "over" the vehicles any more, but ultimately what I think doesn't matter, what's law is what matters. What constitutes flying "over" something?