I think Keith is getting a bit concerned about my daily problem with tractors cluttering the local dual carriageway during my trip to work. His mind has been on the task and he has come up with a novel solution:
An air to ground heat-seeking missile tuned in to tractors' exhausts!
Sounds good to me. I had been considering the ancient Romans' idea - knives attached to my chariot (sorry - car) wheels carefully positioned to catch them as I overtake, but the heat-seeking missile - oh yes, I like the sound of that.