MIL STD- Transportability Criteria

5.1.6 Cargo tiedowns
Items transported on cargo vehicles need to be secured to prevent movement and damage during highway shipment. The items need to be secured to:
.7 times the weight of item in the forward longitudinal direction:
.3 times the weight of the item in the aft longitudinal and lateral directions; and
.5 times the weight of the item in the vertical upward direction.
The forward longitudinal requirement was derived from the vehicle-braking requirement in the Title 49 CFR. The other requirements were established based on standard Civil Engineering practices for safe highway design.

If the vehicle itself, with its payload, is going to be transported, the payload (secondary load) must be secured to the requirements for planned transport modes. The payload becomes the secondary load, with the transported vehicle being the primary load. The secondary load restraints required for highway transport are not as restrictive as those required for other modes.