Spending time at Dunsfold on Sunday gave me a chance to ask others about Dog Guards and Life Guards.
An overwhelmong majority, 18 out 19 of long time bus owners and experienced bus operators knew the under PCV /PSV vehicle guards as Life Guards.The 19th person called them underrun guards, a name appropiate to trucks side guards.(see DVLA testers manual)
It would seem the bus guards in question are not Dog guards and have nothing to do with dogs.
Long live the Life guard!
Peter