This thread seems to have gone down a mainly train crew focused route, but there are also a number of examples of ‘depot lottery’ creating a disjointed/imbalanced service pattern early in the morning or late at night where all the trains seem to run in one direction to get them to or from a depot, leaving the service in the opposite direction extremely sparse.
The North Wales Coastline beyond Llandudno Junction at Bangor and Holyhead exemplifies this perfectly. First eastbound departure from Holyhead towards Chester is the 0421 to Cardiff. The last Eastbound departure towards Chester in the evening is the 2031 to Crewe which gets into Chester at 2227. Incidentally on Sundays theres a later train at 2140 ex Holyhead
Meanwhile in the opposite direction Westbound along the coast the first arrival into Holyhead is at 0823 - an avanti service ex Birmingham. Whilst the last westbound along the coast (2320 ex Manchester Airport) departs Chester at 0038 getting into Holyhead at 0212. So quite poor for those wanting to head West along the coast in the evening.
Meanwhile down in the Rhymney Line in South Wales, theres numerous stabling sidings in Rhymney which leads to some odd deviations from a 1tph
(plus peak extras) timetable on Monday to Saturdays. The first Southbound services from Rhymney at 0612, 0632, 0700, 0724, 0743 are all formed off of Rhymney sidings so the first arrival from the Cardiff direction is not until 0831 ex Penarth.
There is broadly an hourly service throughout the rest of the day towards Cardiff with the last train Southbound at 2116 from Rhymney. Except theres a
gap of 2.5 hours in
southbound services between 1727 and
2000 as 3 consecutive arrivals from Penarth go straight into the sidings to stable for the night. Presumably thats the most efficient way of organising the timetable to avoid ECS movements to/from Cardiff, although i dont if crewing arrangements on the Rhymney line also dictate this service arrangement. The line South of Bargoed retains at least a 2tph service throughout the evening btw.