What is the minimum amount of rearward force that a cargo securement system must withstand?

Each cargo securement system must be able to withstand a minimum amount of force in each direction.
Forward Force = 80% of cargo weight when braking while driving straight ahead.
Rearward Force = 50% of cargo weight when accelerating, shifting gears while climbing a hill, or braking in reverse.
Sideways Force = 50% of cargo weight when turning, changing lanes, or braking while turning.
Upward Force = 20% of cargo weight when traveling over bumps in the road or cresting a hill.
This requirement is satisfied when the cargo is "Fully Contained."