Caution Horses

So, we're driving back down the motorway on Sunday and we pass a huge van with the above message on the back. 

For a moment I had this vision of a the van containing a pair of specially trained equines who turn up when you do something stupid and say things like "Just this once, we'll let you off. But if you'd better not do it again". 

After some discussion we decided that it could also be an instruction to pull into the next field and tell the occupants not to eat grass like that, or whatever.