The more bulky Auto Transport that Uhaul rents has surge breaks but the small tow dolly has nothing
ugh....not much for choices....have you checked penske or other national rental places ?.......
Another possible option, would be to flat tow the impala.....but you'd have to check the owners manual to see if it is ok, and possibly modify the impalas front bumper area to connect the tow bar. cars can't be flat towed. Some vehicles can't be safely flat towed. You'd also have to leave the steering wheel unlocked so the front tires can move as they need to when turning.
It's not hard to do, is get a tow bar and flat tow the car. You'd have to check with every state you'll be going thru to see what their laws are on it, and you may have to modify the cars front end to attach the tow bar.
I flat towed a 6000 lb 4x4 from upstate new york to the SE corner of VA with a tow bar........and I towed it with the truck in my avatar on 40" swampers no less.
I used a towing harness extension to connect the towed trucks lights to the running truck (parking, brake and hazard, NOT headlights) so that when I put on the turn signal or hit the brakes, the same lights on the towed vehicle came on. I also wrote IN TOW on the back glass in huge white letters.
While I could have just put the t-case in neutral (NP205) in the towed truck, I instead opted to remove both front & rear driveshafts to make sure there were no problems.
I had no issues other than REAL lousy MPG (the truck only got 10-11 mpg at best not towing), but what do ya expect from a ~6000 lb truck with ~500 hp engine, 40" tires, and all the aerodynamics of a barn ?!?
The benefit of this method, is you do not have to worry about tongue weight cutting into cargo weight.......but you do have to still meet the tow capacity of the truck, and don't exceed the capacity of the tow bar either (shouldn't be a problem with the impala).
Should even be cheaper than renting the big auto transport dolly or smaller dolly too.
Backing can be tricky, but it's doable if you go slow and use your head, and you do have to consider where and when you park if not in an area designed for such rigs.
BUT, you also don't have the benefit of any extra brakes (electric or surge) when in the mountains. If I had any issues like that, my plan was to just drop it in 4 low and creep using the engine braking supplemented by the regular brakes, but I had no issues at all.