We have a large red sign on our back gate - BIOSECURITY DO NOT ENTER - plus a foot dip in a bright red bucket right in front of the gate. Today the oil delivery came and our tank is a few yards inside the back gate. We had spoken to the delivery company in advance for them to let the driver know he was to dip his feet.
So he arrived, squeezed past the foot dip without using it, opened the gate with the big sign on and marched straight through. He didn't have a clue what I was talking about when I asked him to use the foot dip (a bit late I know but it was to make a point) and he was amazed when he went back and looked at the sign on the gate - he just hadn't seen it. He probably would have missed the sign if it had been in flashing dayglo orange, with red stop lights. So he had been making deliveries in a rural area, where there are plenty of poultry keepers, for three months without taking any precautions against transferring disease. I'm sure he's not the only one, and I'm sure by his blank face when I was telling him about Bird 'flu that he won't remember a word when he makes his next delivery.
What can you do? Just your best I suppose