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Safety Testing of London’s Underground With cRIO & LabVIEW

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Original Authors: Anthony Afonso, Thales UK

Edited by Cyth Systems

Thales UK using NI CompactRIO hardware and LabVIEW software to perform safety testing of London Underground rails.
Thales UK using NI CompactRIO hardware and LabVIEW software to perform safety testing of London Underground rails.

The Challenge

Upgrading traditional methods of testing the rails used in the London underground system, which has traditionally been costly to revenue and time.

The Solution

Automating the testing of rails used in the London underground system and automating the communication of rail health and integrity with the use of virtual test trains (VTTs) created by using NI CompactRIO hardware and NI LabVIEW system design software. This is used to mimic an actual passenger train while saving vast amounts of time and money.


Traditional methods of testing railway systems require the use of a fully operational train and full closure of the track, usually for days at a time. The process is expensive, time-consuming to arrange, and inconvenient to the public. The automatic signaling system upgrade project for the Jubilee and Northern lines promised to boost capacity by 33 percent (the equivalent of carrying approximately 5,000 extra passengers each hour) and cut journey times by 22 percent, according to the Transport for London website. This massive upgrade offered an opportunity to revolutionize testing within the rail industry. The challenge was to generate an alternative testing solution that could alleviate many of the burdens of this traditional method and ultimately lead to a less costly and more time-efficient means of testing new technologies that is in line with the Underground’s highly stringent health and safety policy.

Left: VTT in Use, Right: London Underground

Our Approach

Thales UK is a world leader in transportation solutions, and we were commissioned to install the automatic signaling solution for the Jubilee and Northern lines. The project involved installing a Thales S40 SelTrac Transmission-Based Train Control (TBTC) system on both the track and the entire rolling stock fleet of trains. Before these retrofitted trains could use this new system in service, the track installation needed to be tested. The engineering team devised an innovative test rig that could mimic a passenger train fitted with a Thales TBTC system. It needed to be portable and quickly assembled in almost any location along the Underground. Another goal was to reduce the quantity of test staff and test time so that standard engineering hours could be followed instead of requiring costly weekend closures. From an environmental perspective, the system needed to run reliably in any environment that could be experienced on the Underground network. This can vary from snow and rain to deep, dark, and dusty tunnels. Additionally, the solution needed to be bidirectional to offer a massive advantage during testing/fault finding, thus increasing efficiency and optimizing track time. Finally, the software needed to be intuitive to reduce the impact on test engineers during the transition from real trains to the new design.


The solution was to create several VTTs with CompactRIO at the heart of each VTT system. The VTT system operates as a portable, battery-powered railway trolley that carries a testing staff and the Thales communications equipment used to test the SelTrac TBTC system. It is already installed on the Jubilee line and installation on the Northern line (the busiest on the Underground network) is due for completion in 2014, per the Transport for London website.

The VTT runs with the CompactRIO control system interfaced to custom hardware. We used a CompactRIO real-time controller, an FPGA-equipped chassis, and flexible modular signal interfaces to implement the system, all of which were programmed with LabVIEW system design software. We perform both control and monitoring simultaneously with CompactRIO. For the control we use simulated signals from the interactive dials and switches on the front panel and preset values to imitate a real train. The monitoring portion of the system consists of several assigned test points, signal communication antennas, and CPU serial data, which we record from the VOBC. This platform provides the onboard SelTrac TBTC signaling equipment with the appropriate signals to mimic an actual passenger train, hence the term “virtual test train.” Additionally, gathering of all this data allows us to view how a train's VOBC would react to its surroundings. The reaction of the VOBC is imperative to us since it is this data that allows us to have confidence that the systems were installed and commissioned correctly.

We also programmed data-logging functions in the LabVIEW application to easily record technical data on an SD memory card. We did this in case the data was required for the testing and commissioning of the SelTrac TBTC system. To review the test data, a VTT viewer program was also developed using LabVIEW. This VTT viewer program means that the testers on-site can review data immediately to make necessary corrections and ensure the appropriate signals are monitored.

Communications Based Train Control (CBTC) Signaling System
Communications Based Train Control (CBTC) Signaling System

Success of the New Solution

While initial trials on the Jubilee line were promising, VTTs that are now being used for routine programmed testing on the Northern line have surpassed our expectations. Use of the VTT has dramatically increased and diversified. In addition to serving as a testing tool, the VTT is a useful fault-finding tool. Another major advantage is the VTT’s bidirectional ability: A normal test train is only permitted to travel forward, but the VTT can reverse, and retest missed track, rather than loop around the line, which inevitably takes time. Another bonus is that the VTT can perform testing whilst other work is being performed in parallel. This is not possible using traditional methods because a train requires that power be available on the trackside.

Besides providing the control element, CompactRIO can automate data capture. The user can test, gather data, and analyze it all in a short amount of time, which speeds up testing and commissioning.

The use of the VTT has already proven to be invaluable. Traditional methods that normally take days have now been reduced to hours and require around half the manpower to operate. Our solution, powered by CompactRIO and LabVIEW, has saved vast amounts of time and money, increased productivity, and helped us take a huge leap forward in signaling testing innovation.

Impact of Using National Instruments Hardware and Software

A key factor in the success of this project was the use of LabVIEW. The software offered several benefits, such as graphical programming, easy-to-read code, maintainability, and scalability, that all proved essential for a large project. It also featured built-in tools that reduced development time by providing proven sections of code. Finally, the user interface design, which is usually every programmer’s nightmare, was simple because LabVIEW offered tools for quick customization.

We chose NI hardware due to the versatile, reliable, and high-performance CompactRIO platform. The platform incorporates an accessible FPGA built directly into the backplane of the chassis, which was one of the most valuable features. NI hardware, coupled with the simplicity of programming the PC, real-time processor, and even the FPGA—all with LabVIEW—made us choose the NI platform.

From a software point of view, LabVIEW was the ideal environment to use because of its graphical and intuitive approach to programming. It was simple enough to demonstrate sections of code to someone who had no programming experience, which helped greatly with instilling confidence in our customers and bidding to get approval. The choice of a modular signal interface meant that specification changes and revisions were accommodated by swapping the relevant interfaces, rather than abandoning the entire system. The graphical system design approach not only met our needs but also helped us remain flexible in our methodology while developing a prototype.

NI customer care has always been first-class, and we highly recommend them to potential customers. Overall, from start to finish, NI provided an excellent, complete platform so that we could intuitively and easily create programs to control reliable, versatile, and modern NI hardware.

Original Authors:

Anthony Afonso, Thales UK

Edited by Cyth Systems


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