This type of load occurs primarily when switching freight cars and is taken to be 4 g for normal switching operations and 1 g for intermodal transport in the Guidelines for Packing of Cargo Transport Units, for example (see Table 1).
This places the packaging containers and packaged goods under considerable stress. If boxes are stacked, static friction between the boxes can cause shear stress on the bottommost boxes if there are gaps to the sides. The same applies with respect to the securing of the packaged goods.
Vertical shock loads can occur during handling, for instance if the packages are set down too hard. These are generally brief shocks that are not critical for the packaging itself, because the time the forces are acting is so short, but which can nevertheless damage highly-sensitive packaged goods. In cases such as this, shock-absorbing elements must, for instance, be used to secure the goods inside the packages.