Richard!
I’m telling you, a movable electric net fence (such as “Fast Fence”) around your vehicles, and a high voltage charger (electric or solar) will solve your problem. The shortest fence available (about 164 feet) will easily surround 2-3 cars with enough additional space between cars and fence to further discourage jumping. These go up in a jiffy and can be easily opened to allow access to (or exit of) the cars. (You’ll probably only find these on-line.) This option is much less expensive than the shock collars (for a number of goats) and, I’d bet my bottom dollar, more successful. Let us know what happens!
I first heard the goat episode while driving, (thought I was drive off the road because I was laughing so hard), and I’d like to hear it again. Is there any way to hear it on this website or elsewhere? Thanks.