The dual circuit brakes are a great upgrade. Playing Devil's advocate, you can't argue with the millions or billions of miles these trucks have traveled with a single circuit brake system as long as the operator followed the PMCS chart in the TM. That part is not complicated, there are Before checks, During checks, and After checks and any issue with the truck is to be reported up higher. In our case, higher is our checkbook and while that is unfortunate. If you can't maintain it in roadworthy condition, you can't afford the issues that may come with it haphazardly failing. These are rather slow trucks but I'm sure an engineer will comment, 13,000 pounds rolling at 45 mph will exert _ amount of force upon what it contacts. If what it contacts does not stop it, it will have _ amount of force to keep going. I'm only saying, if you have not pulled your wheels and drums and verified that your brake system is solid, please do. It will not only save another life, it'll likely save yours!!! These things do fine in crash testing so long as it doesn't wind up on it's roof. All bets are off if that happens and since it is a tall truck, the center of gravity is against you and gravity always wins!!!