Originally posted by Wheatfield If they did, the roads would be littered with car parts that had fallen off.
They are.
Anyway, years ago I sailed up the east coast (of Australia) and stowed my SLR, wrapped in a towel inside a padded camera bag, in a locker low down against the hull.
I thought this would be the driest most secure spot (it was).
Later when I went to use the camera, I found one of lens elements had come loose.
Whether this was caused by engine vibrations of the thumping of the hull against waves I don't know.
As to a modern car, unless driving over extremely bad roads, I don't think I'd worry too much but on a seat would be best.