RETB is a cost-effective system for signalling on single track rail networks

With very low track-side infrastructure requirements, RETB Next Generation – Comms Design’s railway signalling solution, has a significantly lower cost per track kilometre than traditional signalling, and a fraction of the cost of many digital train control systems.

Having trains under interlocked operation across the network from a central control centre offers significant improvements in safety and efficiency over physical tokens or timetable working.

RETB has been safely in use since the mid-1980s on the United Kingdom rail network. Comms Design introduced new radio equipment in 2016 which has further improved the reliability and efficiency of the system.


Traditionally, rail routes with long single track sections, light traffic in difficult terrain are signalled using basic or manually intensive systems. For example:

  • Track Warrants
  • Physical tokens
  • Timetable and Train Orders
  • Direct Traffic Control
  • Telephone/Telegraph

These methods of traffic control rely heavily on human interaction, are prone to error and do not allow the track to be used to its full capacity.


Tablet machines for single track working are inflexible and require significant human intervention


Direct Traffic Control is unreliable and prone to accidents due to human error


Track warrants do not permit changes to schedules, limit track capacity and do not prevent unsafe situations

RETB – Safe, economical traffic control, even on rural routes

Comms Design’s RETB Next Generation fills the gap between primitive train control methods and costly, infrastructure-heavy systems:

  • Token issue controlled by SIL Level 4 Interlocking
  • Modern software-based train radios automatically tune to the strongest channel, maintaining high-quality communication
  • VHF radio network covers long routes with only a few base stations
  • Low infrastructure requirements, simple to maintain and secure
  • Entire route can be safely controlled from a single signalling desk

Due to the flexible and compact design of the RETB equipment, the radio base stations can usually use existing available masts and equipment rooms. Comms Design provide a complete radio network planning service which can combine existing radio sites with new sites if required.

All this is backed by Comms Design’s training materials and support programmes, and our commitment to high quality service.

A shared radio site installed with RETB equipment

Comms Design radio planning ensures optimal siting of new base stations

RETB Low Cost Signalling is in operation on over 700km of route in the United Kingdom