You can issue move orders to materials in transit

[TehJumpingJawa]

When a wagon or ship is carrying material goods, you can select the goods as you would a regular unit, and issue a move order to it.
Obviously material goods have no movement points, so this has no impact on the gameplay.

There is however a visible artifact - the cargo has it's status blip change from green (movement points remaining) to red (movement points exhausted)

Not sure if this may also have other side-effects in more peculiar situations...