In November 2009, Rail Engineer featured a new and unique video train- positioning system (VTPS). Developed by RDS International, VTPS provided a fundamentally new approach to train positioning and offered a simple-to-operate, reliable product, with both low installation and maintenance costs, and requiring no complicated lineside infrastructure.
With VTPS, a forward-facing video camera, together with equipment installed inside the train, is used both to measure speed using video pixel analysis and to accurately provide information to position a train. The system is accurate to within, typically, 2 per cent of distance travelled compared to, say, ETCS which is specified for an accuracy of 5 per cent.
One of the key advantages of VTPS is that it is independent of any track or lineside infrastructure, other than existing fixed reference points.
RDS has developed a new real-time driver support system (DSS) utilising VTPS which has now successfully completed user evaluation trials. Part-funded by RSSB, the system helps drivers to learn and retain route knowledge information and provide additional information on demand.
DSS displays a rolling railway map to help train drivers anticipate the route ahead. The map is displayed on a tablet, showing the location of key information including stations, signals, junctions and speed restrictions for the route ahead. The design team has worked closely with passenger and freight operators to achieve a layout which presents key information clearly at a glance. The system allows drivers to operate with confidence in less familiar situations, for example when a train has to be diverted off its planned route.
Being able to display accurate data and information to the driver requires an accurate train positioning system. This could not be provided by a Global Navigation Satellite System (GNSS) alone, since this would not provide positioning in tunnels, nor adequate positional information to determine which line the train is on.
Lineside beacons are expensive to install and maintain, are a hindrance to track maintenance, and require additional equipment on the train to receive locational information. VTPS and DSS overcome all these disadvantages with minimal train fitment requirement. This makes the task of retrofitting the system to existing stock relatively simple. RDS is a young company with new innovative ideas, but it is built on solid foundations. The directors and engineers have extensive experience, gained over thirty years, implementing major railways projects involving electronic equipment installed on trains.
Two cameras, with one for redundancy, are attached to the inside of the cab windscreen. The camera image is transformed from a horizontal to a vertical view, giving a picture that appears to look directly down on to the track. Connected to the cameras is an image processor which can be some distance from the camera. The frame image is divided into a matrix of blocks and pixels, with one pixel covering an area of ground approximately two centimetres square. As the train progresses, the system looks for the displacement of pixels with the same patterns in an earlier frame, and is able to provide accurate positional information.
A major feature of the system is that it is not dependent on any external equipment or radio signal. It will work anywhere using fixed reference points which the camera will read. Measurement will start from this point and continue until the next marker is reached.
There is no prescribed distance between markers and they can be existing structures or any known reference point which the camera can recognise. If the track is already fitted with beacons or balises for another purpose, then these can be fed into the video positioning processor as required.
Designed to meet and exceed the performance requirements for ERTMS odometer and speed measurement, VTPS can support other applications, such as standby signalling systems at low cost, as well as DSS.
Some forms of railway system failures can be worked around through diversion of a train onto a different route or line. Current operating practices prevent drivers from operating over such a route unless they have ‘knowledge’ of the intended route (route knowledge).
This is normally gained by the individual driving the route a number of times over a set period. There are some diversionary routes which are relatively straightforward but may not be able to be used because of the current rules.
RSSB research study T665 (risks associated with working trains during degraded modes of operation) investigated whether moving to a risk-based approach could lead to a greater degree of flexibility to enhance service reliability. The study identified that the network utilisation benefits are much greater than any safety impacts, so long as lower speed running (~20mph) is implemented and route information packs are provided. DSS was developed with this in mind and to provide route information in a user-friendly format.
DSS is an application to help drivers, not to replace them or tell them what to do. It can provide the type of support that hitherto was provided by a driver’s assistant, without compromising the driver’s responsibility. For instance it can also provide reassurance that a driver hasn’t inadvertently missed a speed restriction – no matter how experienced and knowledgeable a driver may be, human fallibility is always possible. DSS demonstrates the industry’s continuous investment in its aim to improve safety, in the same way that the railways have always done over the last 150 years.
Other business benefits of the system are that DSS will speed up the process of driver training and continuous assessment. Rapid access to additional information for use in emergencies is possible as it has the potential to update the system in real time with, for example, temporary speed restriction information.
This may provide a cost saving to the infrastructure manager and reduce any risk to lineside staff. Another side benefit is that the system has a month of recorded video on board, so stock without a forward facing camera will gain this facility when DSS is provided.
DSS development and trial
Led by RDS, along with partner First Great Western (now GWR) and sponsored by RSSB, the project to specify and agree the user interface started in early 2015. Trialling of the system followed in June 2016, and has recently concluded. The trials set out to evaluate the user interface by testing with drivers in a train simulator, and to evaluate the system using an in-service train.
RDS has developed the system in house and have control over all of the software and hardware. CCD Design & Ergonomics Ltd assisted with the user interface design.
A DSS user group was established consisting of drivers/driver managers from four train operators and one freight operator as well as representatives from Network
Rail yellow plant operations, RSSB operational standards and human factors. Several different interfaces were evaluated before agreeing on a vertical format of the line ahead displaying route information.
A number of operational modes were agreed, with more or less information being displayed according to the selection. For each mode, the features chosen for the display to a driver were carefully considered along with any safety issues. The modes include:
DSS presents critical route information to assist when signalled onto an infrequently used line, for example following an operational incident, commencement of a planned diversion, or a railway system failure.
Designed to cater for both high speed running and when driving at caution, it presents the train position with signals, stations and line speed changes ahead. It shows the current track name, route mileage and line speed plus the next line speed and a distance countdown to the next signal. This mode also highlights the route to be taken at diverging junctions, based on journey information entered by the driver, and the possible routes that could be indicated at a junction signal. DSS allows easy selection between different map scales, day and night display, and icon preferences.
The DSS presents the rolling track map with the move highlighted ahead of the train’s location and exactly how much further to pass a shunt signal. It displays the limit of shunt, the signal to ‘drop behind’ and other shunt signals. A distance counter indicates how far the train rear needs to travel to be clear.
If an unplanned stop is made in an unfamiliar location, then Static Mode can be selected. The DSS displays the current position on a track schematic complete with GPS co-ordinates.
The driver can toggle on and off local railway access points, bridges, tunnels, signals, line speeds, track electrification status and site specific communication information. This would be very useful if it is necessary to detrain a passenger service.
Once the DSS user interface was agreed and designed, a series of tests was carried out using a Class 43 HST simulator. In order to determine a baseline, a driver who had no knowledge of a route drove it on the simulator under the guidance of a Route Conductor (RC). Further tests were undertaken with drivers having no guidance from an RC and just assisted by the DSS. The simulation tests concluded with a run driving in thick fog with the driver having no situational awareness from looking ahead through the cab window so having to rely totally on the DSS.
The results of the tests revealed no substantial difference in the way the train was driven along the route. The system was well received by all who experienced it with comments on its usefulness.
The trial concluded with a series of live testing runs with the system installed in a GWR Class 43 HST on the Bristol to Cardiff route. The DSS was monitored by a driver manager and it was concluded that the system delivered on all its requirements straight out of the box.
The DSS demonstrator trial gathered more than sufficient evidence to confirm that the concept is valid.
Typical uses of DSS
Scenarios for the use of DSS may include the following:
» A tree is on the line ahead and trains are stacked up behind. It’s been four hours and everyone’s getting hot and bothered. It’s time to evacuate the train before passengers take matters into their own hands. The driver checks the DSS for the nearest access points and provides the signaller with the train’s GPS co-ordinates so that help can be directed to the right place.
» Five miles up the track a train has broken down. There’s a junction ahead and the signaller has routed the train so it can be terminated at the next station. The driver has not signed for the two miles of route to the station but, with the DSS, he is able to drive the two simple track sections.
» A train is shunting from Platform 1 to Platform 7 and the signaller instructs the driver to leave the station and drop behind shunt signal SH1234. The driver believes he knows where that is but he switches DSS to shunt move and he is now very clear on what is required.
The next stage is likely to be more extensive operational trials, possibly on a compact route with captive rolling stock, and with multiple ‘real’ users. In parallel, RDS is looking for easier ways of incorporating data into DSS from existing asset information systems. RDS would welcome input from train operators who may wish to help sponsor and bring to the railway this exciting, simple to use and install, inexpensive digital rail enhancement.
Could VTPS and DSS provide the elements of a standby signalling system for ERTMS and future rail? Well, they have the vital ingredients of simplicity and independence from other systems, just what is needed for any back up system.
Written by Paul Darlington