Fifty animals

I read Mary Beard's blog about the animals in the road sign with amusement as I'd seen this sign on the M4 on Sunday. She was asking whether it means fifty animals are on the road. I take comfort from the grammar: the capital A denotes the start of a sentence. Were "road" to have a capital R, it would be ambiguous, but it does not. Nevertheless, neither of us saw any animals roaming on the motorway. I did see a couple of horseboxes though. Perhaps that's what it refers to? After all, if there were cows on the road, you wouldn't want to drive at 50MPH, would you? If there were a truck load of animals going to the slaughter house, would they be treated with such deference?