A letter from Derek Buttivant
1. The report on platform curvature contains much complex data and, as is usual in consultant's reports, quite a lot of material which is obvious to everyone.* As is also usual, some of the findings are dubious. Particular mention is made by Peter Murnaghan of the Looe branch platform (No.3) at Liskeard. As most CRS members will know, that platform is far longer than is needed for the present usual train length of one or two coaches. Any more than two coaches and the train is too long for the platform at Looe. In the days when 3-car dmus sometimes worked the branch, passengers in the rear car had to walk forward to alight at Looe. In fact, most of the over-long Liskeard platform is perfectly straight. The curved section at the far end, nearest to Coombe Junction, could easily be demolished without any impact on present or foreseeable future normal use. The consultants' report, however, recommends (page 31) realignment of the track - which would be pointless.
2. There are significant problems when introducing new rolling stock to lines and through stations built by different railway companies over many years. British Railways tended to build stock such as the Mk1 coach and the class 150 dmus to dimensions that would fit more or less everywhere on the system. That principle has been less in evidence in recent years when rolling stock has been ordered for specific routes and operators. The position of doors has a significant effect on train-to-platform stepping distances. Class 153 units and HST Mk3 coaches, for example, with doors at the extreme ends cause problems when on "convex" curved platforms while vehicles (such as Mk1 coaches and class 150 dmus) with doors towards the centre of the coaches can be problematic at "concave" curved platforms. The new IET coaches are even longer than Mk3s at 26 metres but the doors, while still at the ends, are not at the extreme ends, thereby alleviating the problem slightly.
3. Passenger accidents are a potent driving factor behind rules governing door opening and closing and despatch of trains. With HSTs having swing doors, opened and closed by passengers - but locked/unlocked centrally - there are complex procedures for checking that doors are properly closed on departure. Delays occur regularly through Cornwall through implementing these procedures. HSTs are fitted with a rather primitive but functional selective door opening system which requires the train manager to be in a particular part of the train to control door unlocking when stopping at short platforms. Platform length is not the only factor at work: where there are signals at the platform end, account has to be taken of the stopping position when a train arrives against a signal at danger. Saltash up platform is the supreme example where, even though the platform is long enough for four coaches, the signal protecting the single line over the Royal Albert Bridge prevents use of a substantial length of the platform resulting in up HSTs having to restrict door opening to the leading (usually first class) vehicle only.
4. The new IET sets have power doors and a much more sophisticated selective door opening system which can be operated centrally by driver or guard plus software that prevents doors being opened which are not safely at a platform. For this reason, IETs, though potentially longer than HSTs, should be able to call safely at stations with short platforms. Of course, that will still require passengers in vehicles not platformed to walk through the train to alight, sometimes leading to delays. If 10-car (two class 802 IETs coupled together) work into Cornwall, with no gangway connection between the sets it will be important for all passengers wishing to alight at most stations to be travelling in the correct unit.
5. It is now intended that some stopping services in Cornwall and Devon will be worked by refurbished, standard class only, four-coach plus two power-cars HSTs. One of these is already on trials and will enter passenger service in January 2018. New stopping position signs have recently appeared at stations to be served by these trains reading: "HST 2+4 car stop". These are generally at the same stopping positions as the signs for CrossCountry four- and five-car units though some Cornwall stations such as Lostwithiel and St Germans will be served by the short HSTs but are not served by CrossCountry trains.
Many thanks Derek, I am sure that we are all now much the wiser.
*Reference - official documents available to the public - click here.