Traditional freight service is time and cost intensive partly due to complex coupling and train forming processes which require costly facilities. Based on the concept of self-propelled freight cars, a new method of train formation has been proposed: virtually coupled train formations. The concept is based on the idea of using modern electronics and data transmission to run several self-propelled units one behind the other without physical contact but at distances as short as mechanically coupled cars.

The train modules could automatically join or leave the virtual train formation when they reach a junction. This way the advantages of self-propelled freight cars could be combined with those of long loco-hauled trains:

• advantages of self-propelled freight cars: flexibility, no time-intensive coupling processes
• advantages of long loco-hauled trains: reduction of aerodynamics through coupled wagons, increased capacity by occupying only one slot (in a fixed-block system)

Safety of virtually coupled train formations The close distance of the multiple units requires all modules to have the same technical parameters known in the system (weight, acceleration). Approaching a danger point the individual train modules would have to keep at a least minimum braking distance.

• A highly reliable and fast short range communication system to realise the distance control (DECT could be a candidate here)
• A far range communication system with less requirements concerning availability used for disposition (GSM could be suited for this purpose)

Service quality in freight service

Virtually coupled train formations of (LINK!) FMUs could substantially raise the efficiency of providing freight services in railways (time and cost reduction, point-to-point relations)

Capacity

Virtually coupled trains only occupy one slot (compared to several for freight train units running separately on the infrastructure)

Technological

The concept is still far away from technical maturity.

Safety

There is obviously a number of safety issues associated with virtual train coupling.

Transition costs

Introduction of a completely new system in freight traffic is costly. For the system to work efficiently a critical mass of equipped vehicles has to be reached.