I have a chain that runs across the back of my truck. The dogs are chained towards the center so that they can't jump out and choke themselves nor put their heads over the sides. I was told that dogs get alot of cataracts and eye damage in the long run from bugs and debris hitting their eyes if you let them hang out of the vehicle. If we have a long trip, I crate them and tie the crates down so that they can't move in an accident.

I live in a farming town...what freaks me out is the farmers around here with flatbed trucks...there is nothing but flat back there. And you see dogs laying back there like nothing...or when they're lying on top of the toolchest thingy.