I would be worried about someone coming by at the speed limit, and winging a bottle at it.. after they turned around..
There was this time we stopped to help someone on the roadside.. there was a plywood highway sign (in the 80s, when 1/2 of you lot were babies) the sign had been hit by a bottle flung out at speed, it had hit nearly neck straight on.. it was stuck in the sign, the neck out the other side off the plywood by about an inch...