Technology Focus series: Automatic Gauge Changing Systems and Network Versatility

Automatic Gauge Changing Systems (AGCS) allow trains to pass automatically between two lines of different gauges. AGCS eliminates the need to change axles or bogies. 

Latest update: September 2019

AGCS is now used for freight trains as well as passenger trains. This provides benefits including shorter transport times, increased competition and increased efficiency. 

What is an Automatic Gauge Changing System?

AGCS allow rolling stock to travel across a break of gauge where two railway networks with differing track gauges meet. The system automatically changes the gauge of the wheel sets on the axle by passing through a gauge-changing facility called a gauge changer, which is built within the infrastructure at the gauge change. This allows rolling stock to travel internationally via various gauge routes without load transhipment or changes of wheel axle.


What industries use Automatic Gauge Changing Systems?

Specifically, AGCS is a technology that has benefited the differing gauges in rail networks. Therefore, the rail industry has been the only industry to use this technology. Talgo, a manufacturer of intercity, standard, and high-speed passenger trains uses AGCS in their Spanish passenger network to overcome different gauges. This is achieved by using a system that initially takes the load of the train body off the wheels and onto auxiliary sleds and track rails on the gauge changer. This allows the wheels to be unlocked and then be guided by a rail turnout to the differing gauge track. The system then locks the wheels at the secondary gauge width and reapplies the load of the train body back onto the wheels, allowing the train to travel on the secondary differed gauge track.

How will Automatic Gauge Changing Systems impact the rail industry?

AGCS could increase the number of rolling stock that can be used on the UK rail network, aiding in delivering a key RTS (Rail Technical Strategy) capability of having flexible freight and low-cost rail solutions. Although there would be an upfront investment of updating infrastructure to implement AGCS, it will reduce operational time and costs as load transhipment and changing of wheel axles will no longer be needed. Deploying AGCS will result in minimal disruption to train services as it allows both freight and passenger trains to seamlessly cross gauge tracks e.g. train from Great Britain into Spain without any stops or interchanges. Furthermore, with AGCS there is no need to bring rolling stock to a halt, and by conserving inertia the large initial energy requirement to get a train moving is reduced. This optimised energy use will reduce emissions.
The development and deployment opportunities of AGCS may have an implication for increasing the interest of foreign investors in UK rail, and/or of UK rail companies in foreign markets.

What uncertainties remain?

Load transfer to auxiliary sleds during gauge changing generates a high level of friction. To accommodate the large amount of heat generated, the current system uses high pressure water jets as a form of lubrication for the friction generated, and thus the thermal energy created is reduced. As a solution, graphene could be incorporated in the composite material of the auxiliary sleds to aid heat dissipation. 
Rolling stock equipped with current AGCS technology can travel through gauge changers at 10km/h. As the technology develops, this speed should increase. This would in turn decrease journey time, thus increasing efficiency. The current top speed for trains equipped with AGCS is currently at 270km/h as the wheels are ‘locked’ in place by a system – not bolted on like traditional methods. 
The cost of updating infrastructure to incorporate gauge changers and replacing bogies with AGCS is currently high and has limited adoption.

What is the current state of R&D?

Current AGCS technologies are presently only applicable for passenger rail as the load on the axle is far less than that of freight trains. TRIA Railway (a rail group specialising in track superstructure, facilities, consultancy and R&D), is leading the Spanish ANGAC37 (Automatic Narrow Gauge Changeover System) project. This is based on the development of a new variable gauge bogie which allows freight transport from narrow gauge networks to wider ones without load transhipment or changes of axle. The testing of this axle was completed at the end of 2016 and has now been commercialised. This new technology will reduce the need for freight to stop at gauge borders, similar to how AGCS has done for passenger rail. This could allow freight trains to move between several countries that use different gauges. At present this variable gauge is valid for the Iberian, Russian and Standard gauges. This could eliminate the load breakage points thereby shortening transport times and in turn improving competition and efficiency.  

What should the rail industry do?

The rail industry would benefit from conducting a cost benefit analysis of implementing AGCS into freight rolling stock. The results of the analysis may prove that updating infrastructure and the time and costs associated could be favourable compared to the reduced time and cost of seamless interchange at gauge borders. 
Research into improved heat dissipation/lubrication methods could be undertaken. This could help to provide alternate methods with dealing with the vast amount of heat generated by the friction. Especially for AGCS for freight trains, as the load is far greater.



Log in or register to keep reading
Register for free individual access
  • Unlock research, articles and more
  • Get updates on RSSB’s activities





Need some help?
To talk to us about accessing RSSB content or corporate membership:
Cookies help us improve your website experience.
By using our website, you agree to our use of cookies.