Every delivery maps a one-off business event and is represented in the system by a unique document. You can reuse vehicles and transportation units (TUs), on the other hand, as many times as you want to. If, however, you want to make vehicles and TUs unique, you use shipping and receiving activities (S&R activity).

When ERP receives a shipment with delivery items assigned, the system automatically assigns the delivery items to a TU. See Integration of ERP Deliveries in Shipping and Receiving.

You can manually assign every delivery to a TU and S&R activity in the transaction Maintain Transportation Unit (/SCWM/TU). You can also automatically assign deliveries to TUs using advanced shipping notifications. In both cases, the system copies the external vehicle number into the delivery when either you or the system assigns this delivery to a TU that is assigned to a vehicle.

When you manually assign a delivery item to a TU, the system checks whether the combination is valid. If the transportation planning type is the same, and the transportation planning system is the same (if transportation planning or billing is done in SAP TM), then you can assign the delivery item to the TU.

If the transportation planning type is different, or the transportation planning system is different (if transportation planning or billing is done in SAP TM), you receive an error message.

You can also manually assign and unassign transportation planning types with SAP ERP.