So, the jig is up for harry the horse as far as cars go. He spent the better part of the last 2 years convincing me that he was afraid of cars and more specifically trucks. He would get all kinds of ants in his pants around cars. So, I was working on desensitizing him to cars. This stopped about 2 months ago. It would appear that is not completely pointless to continue this work. Two months ago Harry followed a truck treating it as lead car (he is off track). I had my suspicion that he may not be totally honest in his truck fear.
Today, he completely blew that into the open. I look out the window at work (which looks out over his pasture). I see Harry settle himself down for a sunbath/nap near the fence line in front of the parked cars. I watch as my co-worker goes out to her truck, which is parked right in front of Harry. She starts the engine and a few moments later pulls out. Harry continues his nap. Then another, larger truck pulls out, followed by the UPS truck. After an hour Harry woke up from his nap and leisurely wondered off. So, I guess he is no longer afraid of cars Which means he gets to be treated like a normal horse without an weird phobias.