In the freight sector, the specific advantages of rail are ideally exploited by long trains transporting heavy low-value mass goods from point A to point B. The specific advantages of road transport are best realised by small high-value goods that have to be transported in small quantities.

During the last decades, the latter type of freight has constantly increased while mass goods have lost importance. For smaller amounts of cargo the conventional production system in railways has been the one illustrated in solution 1 of Figure 1. This system is cost and time-consuming since the individual units have to be coupled and decoupled in shunting points and often have to wait until enough units have gathered in order to form a long train on the main relation. These problems are one of the reasons why the modal split has changed in favour of road transport.

Figure 1: Customer needs and how they are met by different production systems

Source: IZT (based on Frederich, Lege 1996)

The most obvious solution to this problem is to make freight trains more truck-like, i.e. replace long loco-hauled trains by smaller units with a high degree of modularity and flexibility (due to rapid automatic coupling and decoupling etc.).

These shorter units can be realised in different ways:

• Short conventional loco-hauled freight trains
• CargoSprinter consisting of multiple platforms, the end ones of each group are powered by a small diesel motor. The intermediate platforms are unpowered. Several of these trains can be linked together and run in MU (multiple unit) configuration.
• Individual self propelled freight cars: Each wagon is powered and runs independently (usually requiring driverless operation).

The following refers to self-propelled freight cars since they are the most radical realisation of the concept of modular and flexible freight trains.

Self-propelled freight cars have a propulsion unit on-board. This can be realised by electric or diesel traction, the latter being cheaper and better suited to freight traffic running frequently on non-electrified tracks. Self-propelled freight cars could be used for a direct point-to-point delivery of small freight quantities. From an economic point of view, this can economically only be realised by driverless operation. This requires

• autonomous navigation
• automatic avoidance of conflict with other vehicles (replace security control procedure based on fixed railroad sections and visual signalling by telematics applications)
• new shunting methods due to application of telematics and self-powered waggons