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   Virtually coupled trains  evaluated  
Based on the concept of self-propelled freight cars, a new method of train formation has been proposed: virtually coupled trains. 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.
Technology field: Aerodynamics and friction
close main section General information
  close sub-section Description

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.




Such a system heavily depends on information and communication technologies. The communication requirements can be divided into two groups:


  • 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)
close main section General criteria
  close sub-section Status of development: research & experiments
    The concept of virtually coupled train formations is currently studied at the Technical University of Brunswick (Institute for Electrical Measurement and Fundamentals of Electronics).
  Time horizon for broad application: in > 10 years
    (no details available)
  Expected technological development: highly dynamic
    (no details available)
    Raise capacity of infrastructure while reducing production costs and times in freight traffic.
  Benefits (other than environmental): big

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)


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

  Barriers: high


The concept is still far away from technical maturity.


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.

    Success factors:
    (no details available)
  Applicability for railway segments: high
    Type of traction:  electric - DC, electric - AC, diesel
    Type of transportation:  freight
    (no details available)
    Grade of diffusion into railway markets:
  Diffusion into relevant segment of fleet: 0 %
  Share of newly purchased stock: 0 %
    (no details available)
  Market potential (railways): highly uncertain
    The concept is presently too far away from implementation stage in order to assess its market potential.
    Concept not realised yet.
close main section Environmental criteria
  close sub-section Impacts on energy efficiency:
  Energy efficiency potential for single vehicle: (no data)
  Energy efficiency potential throughout fleet: (no data)
    Energy efficiency potential of virtual train coupling obviously depends on the point of reference. Compared to loco-hauled mechanically coupled trains, virtual coupling will be less rather than more energy efficient. However compared to self-propelled freight cars running separately, virtual coupled trains will have much better aerodynamic behaviour. The quantification of this effect depends on many parameters and is not possible in a general manner.
  Other environmental impacts: neutral
    (no details available)
close main section Economic criteria
  close sub-section Vehicle - fix costs: medium
    IT and communication equipment.
  Vehicle - running costs: (no data)
    (no details available)
  Infrastructure - fix costs: (no data)
    It is presently not clear what additional infrastructural equipment would be required to implement the system.
  Infrastructure - running costs: (no data)
    (no details available)
  Scale effects: (no data)
    (no details available)
  Amortisation: (no data)
    (no details available)
no data available Application outside railway sector (this technology is railway specific)
close main section Overall rating
  close sub-section Overall potential: promising
  Time horizon: long-term
    The concept is too immature to make a reliable assessment of its future feasibility and energy saving potential, especially since it is closely related to the concept of self-propelled freight cars which is equally uncertain. It is however interesting enough to justify further R&D efforts.
References / Links:  Bock, Bikker 2000
Related projects:
Contact persons:
 date created: 2002-10-09
© UIC - International Union of Railways 2003
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