Is it human nature that most people don’t believe in something until it’s actually happened? Here at Rail Engineer, we’re not known for being cynical of new technology but when we were invited to view Network Rail’s new Mobile Maintenance Train (MMT), it prompted some discussions about the need for such a thing.

Comments such as: “What’s wrong with the way the railway is maintained now?” and “This will be a white (or rather yellow) elephant.” In no time flat we had it parked up in a siding awaiting its fate. Well, the visit was made and how utterly wrong we were. This thing is a marvel!

Described by Network Rail as a ‘workshop on wheels’, the MMT could well revolutionise railway maintenance. The first set entered service in early September, heralding the commissioning of an initial fleet of eight trains. Four sets will be used on the LNE and East Midlands zones, based at Darlington, Retford, Derby and Peterborough. The other four will be used on the South East zone, based at Paddock Wood, Romford, Woking and Horsham.


These state-of-the-art engineering trains are designed to make working on the railway quicker, safer and more efficient. Each train has three ‘cars’ that provide a workshop facility, two built-in 2-tonne overhead hoists, multiple power points (415V, 110V, hydraulic and pneumatic) and a welfare area equipped with a kitchen, washing facilities and a toilet.

The remarkable feature, however, is the large extendable work area that provides access to the track whilst at the same time protecting the work force from passing trains and the elements. The idea is to provide a safe and contained mobile workspace that will allow track repairs to be undertaken in section, without the need for a possession, and with the adjacent line open to traffic. As a result, the MMTs should reduce disruption during the day as repairs are carried out, thereby allowing better use of the railway at night for freight trains.


They will also keep track workers safe, warm and dry, allowing them to be more productive and better able to focus on getting the job done. Teams will board the MMT at a depot, pre-equipped with all the necessary tools and equipment. They will then be taken directly to the worksite and won’t need to leave the protection of the train until it returns to the depot.

Each 3-car train consists of a Traction & Supply Unit (TSU), an Intermediate Car (IC) and a Mobile Maintenance Unit (MMU).


The TSU contains the No.1 driving cab, the traction equipment, the staff welfare facilities and a workshop area. Motive power is provided by two Deutz TCD2016 V8 diesel engines, of 500kW each, which are mounted beneath floor level along the centre line of the vehicle. There are hydrostatic drives on all four axles giving a top speed of 60mph. Above floor level, a 140kW generator set driven by a Deutz TCD 6.1 6-cylinder in-line diesel engine provides the electrical, pneumatic and hydraulic power for the train. Interestingly, the fuel system includes an AdBlue urea tank, an aqueous solution of urea that is used as a catalyst for the reduction of nitrous oxides in the diesel exhaust.

Power for engine start is from two 24V batteries plus a capacitor array. For battery and capacitor charging, a shore supply can be connected. This can also be used to provide train heating, window demisting and to maintain the fresh and waste water tanks above freezing point.

The fleet is to be maintained by Colas Rail on site. Heavier work though, will be undertaken at its maintenance facilities in Ealing and Rugby.

Colas Rail also had a design input on the driving cab layout and equipment specifications. The cabs are air-conditioned and, as well as having the usual driving controls, are equipped with a sophisticated touch screen DMI (driver machine interface). This provides the driver with various checklists, status indications and diagnostics. A further touch screen device uses GPS positional data and Omnicom Track Locator software to provide the driver with a distance countdown to worksite locations.


In the centre of the train, the Intermediate Car provides a full length storage area for hand tools, power tools and materials. Hydraulically operated lift gates (tail lift seems the wrong description) allow easy loading of plant and materials from ballast level. Heavy equipment can be moved along the train by means of two 2-tonne overhead hoists that share a common track. The track continues on into the Work Unit via a cleverly articulated bridge. Hinged floor plates can easily be lifted to give access to an under floor storage bay that will accommodate up to six rails, with a maximum length of 45ft. The rails are lifted from the four foot using the overhead hoists.

As standard, an impressive line-up of power tools is carried in the Intermediate Car. New to Network Rail are the hydraulic hand tampers, weighing just 25kg each. There is also a 415V electrically powered rail grinder and four rail de-clipper machines. A hydraulic intensifier is available to raise the on-board 200 Bar hydraulic system up to the 700 Bar pressure needed for rail stressing. There is also a portable fume extraction system that is used when rail welding is taking place. No petrol or diesel power tools are used at all.


At first sight, theOLYMPUS DIGITAL CAMERA Mobile Maintenance Unit contains largely empty space, a 16-metre long enclosed work area with no floor. Leaving the Intermediate Car, steps allow direct access onto the track beneath the MMU. The outer end has a similar set of steps leading to an elevated supervisor’s console and the No.2 driving cab. Within the work area, each sidewall is fitted with LED flood lighting and an array of power points for the electric, pneumatic and hydraulic tools. The upper part of each sidewall is almost entirely composed of louvred vents that can be opened and closed by pneumatic actuators. Overhead, the two hoists do their stuff.

The really clever part is the hydraulic system that can independently move each side-wall in and out in six increments of 100mm. With the sides fully retracted for transit, the work area has a width of 2-metres and feels slightly cramped. Moving each sidewall out by 200mm gives the train a standard W6A profile and even this creates a less constrained feel. With the sidewalls at their maximum extent, the workspace feels roomy and is adequate for sleeper changing. Standing in the four foot whilst the sides are retracting feels something like the remake of a tense James Bond scene, but they do stop!

For obvious reasons, the strength and stability of this vehicle is dependent on the integrity of the roof section which is, of course, massively constructed.

When work is being undertaken on the track, the train is controlled from the Supervisor’s Console within the MMU. This locks out the driving cab controls. Indeed, of the three control positions on the train, only one can be in use at any time. Interlocks prevent the train being driven from the driving cabs unless the MMU sidewalls are stowed and the side lift gates are closed and locked. On site, the train can operate in Static Mode or Creep Mode. The latter gives a constant forward or reverse speed of 1.2mph, which is useful for re-matting, re-clipping, etc. At each end of the workspace, a ‘light barrier’ beam traverses the vehicle just above rail level. Breakage of either beam by a person or an object on the track will cause the train brakes to fully apply.


As the sidewalls are extended, a laser measures the distance to the six foot rail, raising an alarm if the gauge is infringed. The amount of extension required depends on the task in hand. Re-matting, for instance, can be done at sidewall setting 2, but rail clipping requires step 3. Welding and sleeper changing require yet more space.

The vehicle end and centre throw needs to be factored in on curves. On the outside of a curve, for instance, achieving an acceptable sidewall extension at the centre point of the vehicle could place the side-wall ends out of gauge.

Andy Keens, project manager MMT LNE, explained more. “At present, the rule book demands that a T3 possession is required whenever the MMT is put to work. Also, we can’t work with the adjacent line open to traffic. The eventual aim, however, is to use the MMT in section protected only by the signalling, for which we will need a rule book derogation. Before this can happen a data base will need to be created in conjunction with ClearRoute for determining the maximum allowable side-wall extension at any location.”

The database will take account of the rail cant, the track curvature, the width of the six foot and obstacles such as bridge piers.


The MMT concept is to move staff, materials and equipment safely, swiftly and directly to the worksite. Once there, the MMU provides a static or rolling enclosed work space, separated from trains and providing protection from the elements. Excellent site lighting is provided for night-time or tunnel working.

Initial tasks will include the replacement of closure rails, removal and repair of track defects, IBJ (insulated block joint) replacement and repair, renewal of pads and insulators, replacement of base plates and fish plate greasing.

Safety is improved because workers travel to and from site in a protected environment. Manual handling is greatly reduced, as is the risk of trips, slips and falls. The use of hydraulic and pneumatic-powered tools means reduced noise and vibration. Reduced road vehicle usage, especially by tired staff at the end of a shift, also adds to an improved safety culture.

The price tag comes in at £5.3 million per MMT set. It sounds a lot, but Network Rail has done its sums well and the project fulfils a business case. The benefits mentioned above bring their own cost savings, but there are also financial gains from increased productivity. For a start, preparation and clear-up shifts are eliminated. Everything is transported to site in one efficient vehicle and all scrap is carried away afterwards, leaving a clean site. Because the job is done in one shift, this means fewer possessions and fewer temporary speed restrictions.

The thinking is also that an improved working environment produces a better quality job. There will be a learning curve, of course. Andy Keens says: “From site observations in Norway, where a similar MMT is operated, we were particularly impressed with the setup time. This has motivated us to look at the options for deploying the machine as a train in section and moving away from possession works.

“We are also looking at the restrictions, limitations and potential hazards with the rail welding process. So we’re considering adopting new safety procedures, fume extraction systems and the use of fire blankets within the MMU. We’ve learned a lot from viewing the welding process in Norway and the potential hazards it presents when working in the MMU.”



On LNE, the acting MMT supervisor is Corey White. He said: “There was scepticism at first, but now the feeling of the lads is that they love it, particularly because it’s taken away all the manual handling. They are happy with the tools and the working environment – it’s like working inside!”

The MMT is planned to be used over much of the LNE zone, but will be particularly useful on the lines with a high proportion of jointed track. This is because the level of required maintenance is disproportionately high relative to the level of traffic. Corey says: “If we get, say, a level two twist fault, we have to respond just as if it was on the main line. Use of the MMT on remote rural lines makes tackling jobs like this so much more efficient, especially as we can look to undertake multiple tasks such as combining track geometry repairs with yearly fishplate oiling. In fact the MMT will allow us to move more towards planned preventative maintenance, rather than just reacting to problems.”

The Darlington-based MMT is currently operating five shifts per week, but the intention is to increase this to seven. Andy Keens reckons it should more than double the current production rate. “With the existing manual methods we might expect to change pads on 300 to 400 sleepers per shift,” he says. “With the MMT in service we have an eventual target of 900 per shift.”

Having seen the MMT and heard about its benefits, the traditional ways of carrying out permanent way maintenance begin to look old fashioned. The MMT is a bold initiative that represents a significant investment. Network Rail has not entered into this project lightly. Forward thinking and new technology like this are bound to attract some scepticism, but everyone associated with the project is confident that this will give way to appreciation.

That has certainly been the case in our office!