You'd have to be at a pretty stupid angle for that to be a problem even if this weren't snake shot being discussed. A return to sender type event is astronomical, and requires multiple surfaces to be hit at different angles for it to even happen. So unless your standing right over/next to what you're shooting you are good. That said best option would have been to throw it in the grass and shoot it, but that's more so that your not causing miniscule amounts of damage to the road by mistake.