Ok, I will go a little deeper into a previous comment. When I am under a load, there is a set time limit in which I have to drive from point A to point B. When I stop for the night, I am often tired enough to attend AJ's needs and my necessities, catch up here and then go to bed.
My truck is made up of the cab area, which is the two seats and a little 8 inch space behind them. The sleeper area is made up of two full height, bolted in cabinets and then a twin sized bed. This is an "open floor" which means there is no wall between the cab and the sleeper. It is walk-through. AJ has a crate, but it stays folded up, inside its box behind the passenger seat unless I need to put him in it. I use it for times the truck is in the shop or in a rare motel room. He crates up easily, but doesn't like it.
He would have to spend 75% of his life inside the crate if I put him in there while I drive. The crate would have to be in the bed area, which means he wouldn't be able to sun himself when he wants to. When I stop at night, I would have to fold the durn thing up and stuff it back into its box before going to bed because there isn't enough space to store an upright crate.
The only benefit (in some opinions) would be him inside a crate. To me, that's not a benefit. He's not livestock. He's my friend. He has a very comfortable bed at the foot of mine where he spends a large part of his time.
My truck and trailer, fully loaded, weighs between 75,000 and 80,000 pounds on an average load. If I get into an accident with that kind of weight, the truck would most likely flip because it is extrememly top heavy due to it's 13'6" height. When a truck flips, there are rarely survivors inside the truck. It's a risk of doing this job.
Since I'm almost always found tooling down the road at around 62mph, I am usually in the granny lane and everybody passes me. The benefit here is less stress to me and better safety for my truck since I am not changing lanes and speeding everywhere.
Again, I weighed carefully the benefit of confining AJ vs. the risk of allowing him loose. He's almost always in the back snoozing on his bed, where there is a rear bulkhead behind him and a bolted in cabinet in front of him, if I hit the brakes, he won't go anywhere. He'll just stand up, shake and give me a dirty look. Sometimes, he's on the passenger seat, where he can't fall on the floor because I have that area built up for him.
Please don't lecture me about how safe it is for a dog to be loose in a semi unless you have driven a truck or are familiar with the construct, operation and physics of a tractor-trailer combination.
I apologize if I've stepped on any toes or offended anyone. That was not my intent.