Title: Book Recommendation Post by: eightf48544 on December 29, 2009, 12:04:04 As well as the German Strassenbahn atlas I also received The
Track Atlas of Mainland Britain: A Comprehenxsive Geographic Atlas Showing the Rail Network of Britain. Published by Track Maps ISBN 978-0-9549866-5-0. Basically it's geographic like Bakers but showing all the running lines, crossovers and junction as per Quail. A must for any serious rail advocate. The thing that surprised me on first examination is the number of odd bits of single track on otherwise double track mainlines and the number single lead junctions (still) even after HMRI made a a recommendation, after a number of collisons, mostly in Scotland, which suggested they should be eliminated. Both may save money but severly restrict potential line capacity. The Melksahm line being a case in point; single track between single lead junctions at both ends. Title: Re: Book Recommendation Post by: Tim on December 29, 2009, 12:27:21 The thing that surprised me on first examination is the number of odd bits of single track on otherwise double track mainlines and the number single lead junctions (still) even after HMRI made a a recommendation, after a number of collisons, mostly in Scotland, which suggested they should be eliminated. Is that correct? IIRC prior to the Bellgrove Junction crash (which I think is the Scottish accident you may be refering to) single lead junctions were not banned, re-modelling that led to their installation merely needed approval from the secretary of state or HMRI (I forget which). The layout at Bellgrove had never been approved because it was changed peicemeal and didn't qualify as a remodelling scheme even thought the layout had in fact been remodelled. The Bellgrove accident report http://www.railwaysarchive.co.uk/documents/DoT_Bellgrove1989.pdf (http://www.railwaysarchive.co.uk/documents/DoT_Bellgrove1989.pdf) does not ban single lead junctions either, it merely closes the loophole which allowed peicemeal remodelling to escape scrutany, ordered BR to "consider the layout with a view to installing trap points", and said the usual things about reducing SPADs including considering ATP, driver preformance monitoring and signal position. The risk of single lead junctions can of course be mitigated by ATP, TPWS, double blocking (as I belive they do in Australia) and trap points although a double lead lunction (or flyover) is better because it does not restrict capacity. For completeness a single lead junction is where a banch (which may be double or single) joints the double track main line as a single peice of track which is used for traffic coming both on and off the branch. A double lead junction allows parallel movement both onto and off the branch. Single lead junctions are easier and cheaper to maintain (fewer moving parts), but come with a capacity penalty and an increased risk or head on collision. Have a look at http://en.wikipedia.org/wiki/Double_junction (http://en.wikipedia.org/wiki/Double_junction) for drawings of various junction layouts. Trap points are points which will cause a train that SPADs and would otherwise be directed onto a collison course (typically onto the mainline) to be either derailed or sent into a siding or sand drag. This page is printed from the "Coffee Shop" forum at http://gwr.passenger.chat which is provided by a customer of Great Western Railway. Views expressed are those of the individual posters concerned. Visit www.gwr.com for the official Great Western Railway website. Please contact the administrators of this site if you feel that content provided contravenes our posting rules ( see http://railcustomer.info/1761 ). The forum is hosted by Well House Consultants - http://www.wellho.net |