Transportation Unit 
The smallest loadable unit of a Vehicle that is used to transport goods. The transportation unit (TU) can be, but does not need to be, part of a vehicle.
The following figure shows different TUs:
Vehicle 1: Semitrailer truck with one TU
Vehicle 2: Truck with cargo area and trailer, in other words, two TUs
Vehicle 3: Train with four wagons, in other words, four TUs
Transportation Unit Definition
In addition to the means of transport, you need a packaging material to create a TU. By linking this packaging material to a means of transport, you define construction rules for your vehicles or TUs. In this way, you define, for example, how many TUs a vehicle is supposed to have and the order in which they are to be arranged. You also specify whether a TU is to be optional or obligatory:
Obligatory TUs are a fixed part of a vehicle (fixed assignment). You cannot assign them to another vehicle, for example, truck cargo area.
You can assign optional TUs to other vehicles, for example, trailer for a truck.
You define TUs in the master data for your transportation planning and execution in EWM.
You can print waybills for TUs.
If you use yard management, you use TUs for inventory management in the yard.
Integration
Before you assign deliveries to a TU, you create an S&R activity for the TU.
In processes with transportation planning in ERP, you can create a TU from an ERP shipment. You can use the ERP shipment number as external TU number.
In processes with transportation planning in EWM and communication to ERP, you can create an ERP shipment from a TU. You can use the external TU number as ERP shipment number.
Before goods issue posting, you can create the current invoice via an invoice request to SAP CRM Billing or to SAP ERP (see Invoice Creation Before Goods Issue).