Oh my gosh this is such a sore point with me!!! My mother-in-law left my son (age 5) in her car not once, but TWICE when she was out running errands - needless to say, I was livid!!!! I NEVER let her take my son out again - she had done stupid things before but this was the worst!! I DID let her babysit but only if she was staying home!!
I also had a similar circumstance as you at the post office a few years ago - a van had several tiny children it it, engine running, kids playing around in the front near the steering wheel - parked on a hill and if the kids had hit the gear shift, oh my gosh - I called the police and sure enough, he said it was not against the law but VERY stupid on the mother's part! He DID reprimand her but couldn't give her a ticket!!
People just don't realize it only takes a split second for a professional to hot wire a car and/or break into it when the engine is running and be gone in a heartbeat!
Yes, I agree there needs to be clear-cut laws because people are just too stupid! It seems people have absolutely NO common sense anymore!!!
As for riding in the back of the truck - I see it all the time. I thot there was a law against it here in Ohio but I've never looked into it. It gets me just as angry when I see dogs in the back of trucks!
I would NEVER leave my children in a car under ANY circumstance!!