My pony has just recently taken up the habit of backing up at cars out on hacks, and when i say 'backing up' i mean really going for it - almost a jog backwards which is really not pleasant at all, he also tries to turn around and go the other way. He does this on his own & in company. He is fine when cars are behind him, its just infront, when he does it and i've tried everything, gentle squeeses to really kicking him on and nothing - he will carry on backing up and a smack with the stick seems to infuriate him even more and make him ten times worse. My friend has got on him too who is quite a more so experienced rider than me and he did it with her too, he has had no bad experiences with cars and when i first had him he hacked out fine with none of this silliness. i just cannot see why he's doing it and what the issue is? 
Has anyone else experienced anything like this, and how do i go about dealing with it? It is really putting me of hacking as it's really not a 'relaxing' and calming experience for me anymore and i feel i always need my gaurd up whilst on lanes incase a car comes. The thing is though, today i took him out and he walked past one convertable car then another came and he would NOT go past it and my friend had to take my reins and drag him and me which tbh surprised me as i didn't think he'd even had gone when she did that. Whats cracking off, help?
Has anyone else experienced anything like this, and how do i go about dealing with it? It is really putting me of hacking as it's really not a 'relaxing' and calming experience for me anymore and i feel i always need my gaurd up whilst on lanes incase a car comes. The thing is though, today i took him out and he walked past one convertable car then another came and he would NOT go past it and my friend had to take my reins and drag him and me which tbh surprised me as i didn't think he'd even had gone when she did that. Whats cracking off, help?