Book Recommendation

[whole diary]

[eightf48544]

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^▸ (Her Majesty's Railway Inspectorate) 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.

[Tim]

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^▸ (Her Majesty's Railway Inspectorate) made a a recommendation, after a number of collisons, mostly in Scotland, which suggested they should be eliminated.

Is that correct?  IIRC^▸ (if I recall/remember/read correctly) 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 does not ban single lead junctions either, it merely closes the loophole which allowed peicemeal remodelling to escape scrutany, ordered BR^▸ (British Rail(ways)) to "consider the layout with a view to installing trap points", and said the usual things about reducing SPADs^▸ (Signal Passed At Danger) including considering ATP^▸ (Automatic Train Protection), driver preformance monitoring and signal position. 

The risk of single lead junctions can of course be mitigated by ATP, TPWS^▸ (Train Protection and Warning System), 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 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.