Dog's travel in car on top of car hauler

I have no issues with the attitude of wanting to be with ones animals during transportation (that is our preference); however, I find no fault in transporting pets in other spaces than where I am traveling because I KNOW (as do humane societies, rescue organizations, etc) it can be done safely. Pets are safely transported in trailers all the time. The car on the car hauler provided better rollover protection than most mobile adoption trailers used by humane societies. My biggest issue would be if the pets were in secured crates. The rest of it will be personal preference, attitudes on pets, and the temperaments of individual pets (some have rock stable temperaments others are more sensitive).