Rolling stock has always been a long-term capital investment. Despite almost continuous operation, often under tough conditions, the service life of a railway vehicle is typically several decades. During that time, a train will be rebuilt and refurbished a number of times.

A series of heavy maintenance programmes will see bogies, traction motors and HVAC (heating, ventilation, air conditioning) systems rebuilt, and the interior will be refreshed when worn out or when the train passes from one operator to another. But what about the control electronics and the traction system?

Reliability and dependability

We are living in a time of rapid change, when operating conditions and the demands that vehicles have to meet are becoming, more and more, topics for public debate. Everything including slow Internet access, delays, and the unavailability of trains becomes a source both for passenger irritation and a loss in revenue.

Passenger demands on rail vehicles have increased so that, in addition to being available, comfortable and safe, trains are now expected to be more environmentally friendly (more efficient, lower noise, lower emissions) and to be fitted with the latest information technology (safe Internet access, passenger information systems). How does this affect your vehicle and its future?

The harder a vehicle is pushed to meet timetable demands and tighter schedules, not to mention increased passenger comfort expectations, the less likely it is that it will last for its full planned life.

One alternative is to use current production technology, as used on new trains being built today, and upgrade either part or the whole of the train’s control and traction system. Bombardier has recently carried out several such upgrades, in Taipei, Toronto, São Paulo and the UK, using MITRAC (Modular Integrated TRACtion system), as used on the latest electric multiple units worldwide.

Evaluation of fleet needs

The first stage in the process is to analyse the condition and configuration of the existing vehicles through discussion with the owner and/ or operator. Statistics taken from maintenance records, and even passenger feedback, are captured and analysed to give an overview of current reliability, identify weak spots, and consider any future obsolescence questions.

On the basis of this information, and an assessment of future operational needs, a specification/proposal can be developed. Systems integration as well as electrical, mechanical and control aspects are assessed and the scope for re-certification established. Using currently available products, such as Bombardier’s MITRAC converters, traction motors and electronics, can ensure a quick and reliable introduction with manageable re- certification.
MITRAC TCMS FamilyFrom the supplier’s perspective, there is a range of possibilities – from the simple supply of products, through partial integration with the current configuration, up to full integration with train control and re-certification.

Introducing new, state-of-the-art technology automatically improves reliability as components will both be at the beginning of their life cycle and have inherently improved durability from the latest designs. For example, in the area of electronics, functionality can now be achieved using fewer components, which also improves system reliability and train availability.


Not only will the need for maintenance decrease significantly, but the maintenance that is needed will also be more efficient. When re-engineering a railway vehicle, engineers have the opportunity to introduce maintenance-friendly products and concepts. In recent years, there has been a great deal of focus on developing easily replaceable modules and improved component layout for quick access and hence shorter downtimes.

There are significant environmental advantages to using the latest technology. For example, today’s traction converters use forced air, water-cooling or car-motion cooling whereas older systems used different fluids or even oils. The materials used in the unit’s construction

can also now be largely recycled (up to 95 per cent), so modern converters are both less hazardous for the environment during operation and more easily disposed of when the vehicle is ultimately decommissioned, compared with older technology.

New functions

One of the advantages of using equipment that is both up-to-date and which has been used in new and refurbished trains all over the world is that there is a wealth of experience to draw from. So whatever an operator might need from his new system, that functionality is likely to have already been developed for another project.

Alerts and alarms, for example, have been made as driver-friendly as possible, and complete new man-machine interfaces (control desks) can be fitted to make the driver’s job as easy as possible.

Traction upgrades present a good opportunity to introduce energy optimisation algorithms. These manage the consumption of energy while accelerating and coasting, and also control its loss during braking, so minimising energy consumption.

Modern diagnostic systems, which seamlessly transfer data over communication links during operation, are essential for the efficient planning of overhauls and for setting maintenance priorities, hence optimising fleet availability.

Passenger expectations

Until quite recently, passengers were concerned with factors such as reliability, punctuality, comfort and safety. Now, connectivity can be added to that list as Wi-Fi access and mobile telephone use become increasingly important. Upgrading train control systems, and the communications backbone that they rely on, can also result in improved communication for passengers.

A well-planned and performed upgrade can extend a train’s service life by10-20 years, giving nearly-new vehicle performance at a fraction of the cost of a new train. Taking a modular approach, and integrating well-proven equipment into the existing train, can result in a high return on investment.

It is important to use equipment that has all of the latest functionality, but which is flexible enough to make integration with an older train simple and relatively painless. Bombardier Transportation’s MITRAC solutions for train control management systems (TCMS) have all been specially developed for railway applications with just this sort of flexibility in mind. They are robust and reliable systems that can perform all of the control, supervision and communication functions required for normal train operation, and are built up from a number of distributed units that can be mounted at practically any location in the vehicle.

Class 317

The MITRAC 1000 propulsion system includes a number of products for medium power applications (metros to very-high-speed trains) and supports all line voltages, including multi-systems. It includes stand-alone products as well as integrated system solutions and the modular architecture allows customised applications, based on standard and proven building blocks, to ensure the flexibility required for modernisation projects.

As an example, Class 317 electrical multiple units are used by several UK train operators and owned by Angel Trains. They are four car units, with one powered and three unpowered cars, and were built at York between 1981 and 1987.

One (number 317722) was chosen as a test-bed to assess the viability of replacing the traction equipment. The primary objectives were to improve train reliability and availability, reduce life cycle cost (LCC), improve mission profile and, importantly, prolong the fleet’s life by 15-20 years.

The scope of the traction upgrade included line and motor converters while retaining the original high voltage equipment and transformer. DC motors were replaced with AC models, which would be more reliable and require less maintenance. Thyristors and traction electronics were removed and new three-phase converters fitted. So, too, was regenerative braking, making the revised unit still more energy efficient.

Compared with the original fitment, the new equipment package gave a reduction on motor overhauls, more efficient fault-finding and even longer brake pad life due to the regenerative braking. The train was lighter as well, further reducing energy consumption and having a positive impact on track access charges.

Testing on the Greater Anglia route showed that total energy efficiency was over 85 per cent when operating at full power, from overhead line to wheels. The regenerative braking returned well over the specified requirements of 30kWh at full load. Performance was similar to the unmodified train up to 65km/h, but was better at higher speeds while also drawing less current.

Old and new trains together

São Paulo Metrô

Another application for refitting a train using MITRAC came in Brazil, as the Metropolitano de São Paulo decided to modernise 156 cars for Line 1. These trains are six-car units and the rebuild included a new traction system with AC motors, new TCMS modular units and software, a new cab front with HMI and overhaul of the systems that were to be reused. Together with integration, manufacturing and type testing, the contract was delivered over 54 months. At the same time, the train received new interior fittings, including a new floor, which allowed engineers to install a new cable route for the TCMS.

The decision to modernise was taken as both the car bodies and bogies were in good condition. The time schedule was a factor, modernising trains is quicker than ordering new ones and the costs are lower. The savings derived from reworking the trains instead of buying new ones was sufficient to buy an additional 100 cars, so the fleet could be extended.

The work schedule was set so that, although trains were out of service, the timetable was not affected and passengers were not unduly inconvenienced.

Viable option

These examples show that it can be both cheaper and quicker to update an old train than to buy a new one. Using tried-and-tested modern equipment such as Bombardier’s MITRAC systems can give operators a train with many of the ‘modern’ benefits of AC traction, regenerative braking, train control management systems, driver interfaces and even lighter weight.

As a result, energy consumption can be cut, maintenance costs reduced and efficiency increased – savings which can more than pay for the updates.

There are, of course, many reasons to update a train fleet, some of which can only be addressed by replacing it with new stock. However, in many cases, modernisation is an attractive option which can be carried out quickly and can extend a fleet’s life at low cost.

Written by Ola Torstensson, platform manager, Jon Vegas, bid manager, and Torbjorn Jonsson, project manager at Bombardier Transportation.