Single-Line Solitaire

Welcome to 2016, let’s hope this will be a happy new year.

Windows Patience Screenshot
Computerised Patience – The Card Game
Windows PCs have, for some time, featured a number of fairly basic games, such as ‘Minesweeper’ and ‘Solitaire’. The latter is a card game which appears to be the same as one my parents referred to as ‘Patience’. The object of this game is to organise the whole pack of cards into four piles, one for each of the four suits. The cards in each pile also have to be in the correct order (Ace at the bottom, then 2, 3 etc. through to King). There are rules about how to set up the cards and where they can be moved, which means that depending on how the deck is shuffled it may not be possible to complete the game. You can also make a poor move which ‘snookers yourself’, the game in the screenshot looked like it was going well but I eventually got stuck. Unlike real-life though, in the computer version there is an undo feature, and I was able to complete the game after undoing a good number of moves and trying a different approach. If you find you can’t complete the game, you give-up, re-shuffle the cards and start all over again (hence the name Patience, I suspect).

What has this to do with public transport in Wales, you ask? Well, I have been trying to produce a timetable to illustrate my aspirations for rail services from Carmarthen and it is trying my patience. Unlike the game Patience though, I am not sure whether it is possible to deal the cards in such a way that everything will work the way I want it to. There may have to be compromises, but how can I prove whether that is the case?

Spreadsheet timetable development
Computerised Patience – Yet Another Timetable Attempt
My problem, or one of them at least, is the single-line sections on Pembrokeshire’s three branches. The ‘main line’ from Swansea to Carmarthen, and from Carmarthen to Clarbeston Road, is double track apart from short stretches in and out of Carmarthen station. It therefore isn’t too difficult to plot an hourly train between Swansea and Clarbeston Road, with extras between Swansea and Carmarthen to boost that section to a broadly half-hourly service. However, the Pembroke & Tenby branch (from Whitland to Pembroke Dock) is single track with just one passing loop (at Tenby) and the Milford Haven branch (from Clarbeston Road) is similar; just the one loop (at Haverfordwest). The Fishguard branch is perhaps the easiest since, despite the sole double-track section (at the Trecwn RNAD junction, where there is no station) being impractical for passing passenger trains, it is relatively short and I’m only trying to path a 2-hourly service (Milford I’m trying to make roughly hourly). The challenge with Fishguard is making connections with TrawsCymru bus services to/from Aberystwyth at Fishguard Harbour. These currently don’t exist, but I’ve worked them out independently and they need to arrive at xx:32 (32 minutes past the hour) and depart at xx:41. This means the trains must arrive between xx:21 and xx:26, and depart between xx:42 and xx:52. This makes the ‘Fishguard Flyer’ boat train, which needs to be about 10 minutes earlier (westbound) and 10 minutes later (eastbound) than the regular pattern (due to signalling headways on the double-track sections), rather difficult.

Anyone got any tips?

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