Driver Advisory Systems (DAS) are becoming established as a useful operating tool in the thrust to achieve improvements in train running performance. First Group have led the way with DAS implementation and an article describing the usage and experience appeared in issue 104 (June 2013). Since then, other train operators (London Midland, SW Trains and Freightliner) are investing in the technology and seeing the benefits that it can yield.
DAS, in its simplest form, enables the driver to monitor the timetabled path of a train to ascertain whether the train will reach its next timing point on schedule and to give an advisory speed for this to be achieved. If the train is running early, then a lower than normal speed is displayed so enabling fuel and energy consumption to be minimised. Similarly, if the train is late, then a higher advisory speed can be indicated if the line and train speed limits permit this. The benefits are twofold: getting a train to arrive at the correct point in time can avoid timetable conflicts with other trains; and it can avoid the need to brake at adverse signals, thus saving wear and tear.
The system works by having an on-board device that is loaded with timetable data for the particular route and comparing this with the actual train position derived from a GPS (Global Positioning System) receiver. GPS signals are typically processed every second and give a positional accuracy of between two and three metres.
The systems in use so far use standalone equipment purchased from one of a number of suppliers and require a driver’s interface panel in the cab, a separate DAS equipment box and a GPS aerial to be installed. Although relatively simple, any task that involves altering a train’s configuration can be complex and disruptive. Would there be a simpler way of achieving DAS by using an existing piece of train kit? Siemens certainly think so and a visit to their Poole premises looked at the opportunity.
Adapting the GSM-R mobile radio
The roll out of the GSM-R network to replace the ageing NRN and CSR (Cab Secure Radio) systems is now virtually complete. The lineside aerials and mast infrastructure is in place and the radio control hubs have been commissioned. A standard design for the train mobile radio was agreed a while ago and the sole supplier for this unit has been the Siemens mobile radio factory at Poole with some 9000 units having been delivered. This radio is now proving very reliable in service and has an MTBF of 300,000 hours. Plessey (before the acquisition by Siemens) had previously provided the CSR cab radio equipment and the new GSM-R sets are designed around that functionality so as to be familiar in operation to the drivers.
However, the processing power used for the voice call and associated identification requirements is only about 20% of the total computing capacity. Could the same radio and display be used for other applications including DAS? Early investigations were encouraging and work began in earnest to prove the concept. An early decision was to use the DAS experience that Siemens had gained in Germany rather than seek an alliance with one of the existing UK DAS suppliers.
The radio must be capable of storing the UK National Timetable, known as the ITPS (Integrated Train Planning System), which is compiled twice a year but updated every 24 hours to take account of engineering works and any other disruption. This amounts to 4Gbit of compressed data and the radio has enough memory to hold this.
Next, the radio has to have the capability of reading GPS signals. Changing the train aerial to accommodate GPS as well as GSM-R is a relatively easy task and can be done at a depot during a nightly maintenance visit.
Accommodating DAS information on the existing mobile radio information screen proved not to be a problem. The screen has 4 lines of display each of 20 characters. DAS information has for the moment been constrained to only 2 lines and shows:
- The current time;
- The time scheduled at the next station or passing point with an abbreviated name for that location;
- The suggested speed to reach that point at the right time (only shown if this is different to the current speed of the train);
- A marker to remind the driver if the train is scheduled to stop there.
The radio must also hold data specific to that type of train such as maximum speed permitted and braking characteristics. This will prevent DAS information from showing a speed that is incompatible with the train specification. It was also important that the provision of DAS requirements has minimal effect on the voice call performance of the radio, the only necessary alteration being the adaptation of the display screen.
The theory, whilst fine, needs to be put to the test on the real railway. Siemens reached an agreement with Abellio Greater Anglia for a trial to be conducted on the Liverpool Street to Norwich route with one Class 90 locomotive and its associated DVT (Driving Van Trailer) being equipped.
A number of drivers have been trained on DAS usage and after a period of familiarisation, results over several months are encouraging and the benefits are becoming clear for all to see.
At journey start, the driver goes through the normal routine of entering the train description (run number) for the forthcoming journey into the GSM-R radio which then co-relates this to the radio identity of that piece of rolling stock. The DAS element uses this information to extract the timetable data for the journey as well as the train characteristics.
It has to be remembered that DAS is only an advisory system and must not conflict with the safe driving of a train. Thus, if a voice call between the driver and signaller is taking place, this has to have priority so DAS information will be suppressed. Equally, if a train begins to brake because of adverse signals, then the same will happen. If the train is running very late and it becomes impossible for it to regain correct time, then DAS will not attempt to show unrealistic advice.
For the trial, timetable data is loaded on to the radio units directly from a laptop computer at the train depot once a week. When fleet fitment begins to happen, then the timetable and temporary speed restriction updates will be loaded via the GSM-R radio link using a circuit switched connection. The limited data capability of the radio system means that several minutes are required to update each train, which will be acceptable for a smallish fleet but impractical for a national roll out. Siemens has a solution for this currently under development, which will be explored later.
The Greater Anglia trial has demonstrated that worthwhile energy savings can result by logging the train power consumption. A typical London to Norwich journey with the normal station stops shows an average instantaneous consumption of 2MW. With DAS fitted and driving to the speed advice given, this reduces to 1.8MW, a 9% saving and certainly worth having.
Connected DAS (C-DAS) implications
DAS in standalone form can never fulfil a truly optimal advice package as it is incapable of knowing the location of other trains that could adversely impact on the approach to junctions and stations. Previous articles have hinted that C-DAS is needed to overcome this, which in turn requires Traffic Management Systems (TMS) to be in place at the signalling centres that will monitor and regulate all train movements. Whilst the nationwide roll out of TMS is to be slower than originally intended, the linkage to DAS is important if the best possible advice to drivers is to be achieved. Once in place, C-DAS will require a high capacity data link to be available to the train radio such that minute- by-minute train running information can be advised and duly processed. Siemens has calculated that this will be beyond the capability of the 2G GSM-R system and reliance on the public 3G or 4G networks will be needed.
A new SmarTrain card has therefore been designed and will include the following features:
- Multiple 3G/4G LTE connectivity;
- An integrated GPS receiver;
- Integrated WiFi connectivity;
- Integrated accelerometers on three axes;
- Increased processing power;
- Increased memory capacity.
For increased functionality and resilience, the GSM-R radio unit will revert to 3G if no 4G signal is available. The data capacity of 4G is enormous and will enable emerging conflict situations to be assessed by TMS and transmitted to the DAS screen almost instantaneously.
Only when C-DAS is up and running will the true value of the system be known, but it is likely that both slow down and speed up advice will be given to ensure optimum flow through rail ‘pinch points’. Siemens knows that it will need to work with the TMS providers to achieve the required interfaces.
With multiple 4G connections possible, the GSM-R radio can potentially be used for even more train monitoring and connection services. These include:
- SureTrack – being developed in conjunction with Huddersfield University, the radio, with its in built accelerometer, will be capable of sensing track voids and unusual vibration that would then be reported in real time to a Network Rail centre. Trials to prove the concept are underway.
- On Board Train Monitoring – the latest trains are equipped with a train ‘databus’ that connects to sensors which monitor various elements of train performance. Any abnormal alarm would be sent to the train company control via an interface to the radio and the 4G connection.
- Passenger Information – the ability to use a train radio to connect a control room direct to the train PA system has existed for some time. However, for various reasons, this is seldom used. With an improved radio connection, it might be time to resurrect the facility. The provision of screens in each coach to give updated train running information to passengers is also being trialled. A 4G transmission link would update information more rapidly.
- Remote Software Updating – using the 4G link to update train systems with new software would ensure all trains are updated at the same time rather than having to wait for each train to visit a depot.
Some of these ideas are conceptual, others are already in being but use independent connection hardware. By employing the GSM-R radio as a ‘comms gateway’, reductions in cost will be possible as well as introducing new opportunities for advertising, business promotion and new passenger facilities.
It is beyond doubt that DAS will be an operational feature of the emerging ‘Digital Railway’. At the same time, the rail industry is under enormous pressure to reduce costs. By using the installed base of GSM-R radios to incorporate DAS operation, this would be one opportunity for cost reduction. Siemens know that this has to be ‘sold’ and will be setting up a demonstration room at Poole with appropriate industry seminars and open days to achieve the necessary awareness.
Thanks to the Siemens engineering team, especially Russell Clarke, Gary Parkinson and Jim Tarrant for demonstrating the capability, and to Jennifer Ockwell and Barry Pearson for arranging the visit.