78
the rail engineer • June 2013
Queueing for a platform means braking to stop at the protecting signal with consequential acceleration once the signal clears. All of this worsens fuel consumption and passenger perception of the journey. DAS should reduce the number of occasions on which this occurs. It must be emphasised that DAS is only an advisory system; the driver is free to ignore the advice being given. It will not impact on the train braking system or its interaction with train protection systems. The principal objective with the current system is lower energy usage and thus less green house gas emissions.
Train equipment and data provision Compared to the fitting of on board signalling systems, TTG’s DAS hardware kit is relatively simple. It consists of: » An on-board processor mounted under the driver’s desk; » A driver machine interface that is a small touch screen bolted on to the driver’s desk; » A combined GPS and GSM aerial; » A power supply connected to the train primary battery that is spike and surge free. Fitting of the First Great Western (FGW) HST fleet has been carried out primarily at Landore, with the GPS/SGM aerial mounted on the train ‘nose’, and each cab can be completed in a single shift. The equipment has been very reliable in service. Other train fleets will have their challenges as to cab layout and space but no insurmountable problems are anticipated. Information for the DAS system is derived from timetable data sources starting with the national UK timetable that automatically feeds the FirstGroup servers in the UK. By this time, all daily and weekly updates to the basic timetable are incorporated including permanent and temporary speed restrictions, dated trains, changed stopping patterns and any different routings. This data is available for downloading to every DAS fitted train. The public GSM system (3G) is used for this. The train knows its location and time at the beginning of the day, these being a given. The driver, after entering the appropriate PIN, keys in the headcode (train description) of the forthcoming journey. The DAS equipment will then automatically be programmed for that
Issue 104 - tre June 2013.indd 78
journey. Should there be a difference in the diagrammed make up of the train, e.g. a longer train, having to run on reduced power, etc. then these changes can be fed into the system and allows automatic adjustments to the predicted operational schedule.
In operation Once the train has reached a predetermined point, typically two miles out from the start, the DAS screen will show an advisory speed to the next timing point, usually a station stop but this is functionally adjustable. To obtain optimum power efficiency, the driver will adjust the main controller to get to this speed. The DAS will constantly monitor the train’s position from the GPS location data but it is unlikely that the advisory speed will change unless anything impacts on the train’s progression. The advisory speed is always less than line speed. Should the advisory speed be exceeded, then the DAS screen will ‘grey over’. Similarly if the route is changed from that which is diagrammed, e.g. the train is routed over the slow line instead of the fast with a different line speed, then the driver turns the system off, as the advice being given becomes inappropriate. Drivers will notice the DAS screen only occasionally since their prime role is to ensure the safety of the train’s progress in line with the signalling system. If adverse signals are encountered and the train is braked, then the DAS advice will ‘grey out’ so as not to distract the driver in any way. If the train is severely delayed, then DAS will not re-calculate and the screen remains blank. If it is a minor delay, then a new advisory speed will be calculated in order to get the train back to timetable as quickly as possible while still seeking to optimise energy usage. After a station stop, the same process applies; DAS will only kick in once a normal speed has been achieved.
Proving and deployment FirstGroup were quick to realise the potential that a DAS can bring. The open access operation, Hull Trains, was the first proving ground as early as 2009. However, this is a small fleet so a more relevant trial was thought to be the Great Western HST fleet. Being high speed trains, the potential for fuel savings was significant. A trial took place between Paddington and Bristol on an out and back working in the period 2009/10. Four proprietary systems were tested and the results were encouraging. After a competitive tendering process, the firm TTG was selected using its Energymiser product. Fitting took place initially on the Hull Trains Class 180 fleet (Adelantes), so as to learn the dos and don’ts, after which the entire FGW HST fleet of 119 power cars was equipped, completion being in 2011. The route data capable of being downloaded covers almost all of the FGW franchise, the only exceptions being the remoter ‘one train working’ branch lines. Getting the drivers to understand and use the system to maximise benefit was clearly going to be a big part of the programme. The need to work closely with the drivers’ trade unions was recognised from the outset. The driving community in general has supported the system in principle. It was emphasised that the system was not there to teach drivers how to drive, merely to act as an aid to driving that could avoid many of the journey perturbations that they typically encounter. Hands on training has been given, this being conducted in the cab on real journeys. A mostly positive response has resulted and with a feedback reporting system in place to suggest improvements. The compliance level is good. The integrity of the system must be understood. There is no interface to the signalling system, the train brakes, or the train protection systems that are found on FGW routes. The driver is in charge and, although the
29/05/2013 14:19