We have the SMI Air Force One supplemental braking system installed on our Honda. When I apply the brakes on the coach, the tow vehicles brakes apply at the same pressure. We also have the 'emergency' brake-away installed too if the car is disconnected from the coach the car should come to an abrupt stop.
I certainly haven't tested the supplemental brake system by doing a 'rolling test', but I would think the car shouldn't hit the coach if I'm applying the brakes on the coach as the Honda should brake too.
While in park, I have had someone press the service brakes on the coach when I'm in the Honda. I can feel that the brake pressure is released at the Honda's brake pedal, hence, the brakes are applied from the coaches air brake system.
MM.
