Posting this here rather than the main South Wales Metro thread to avoid non-confirmed plans potentially confusing people (like I am to an extent). I have some queries as I'm not sure what has got funding/confirmation and what hasn't, as well as what the service patterns will be. I understand that, especially with service patterns, some things are unclear/unconfirmed, but any info would be helpful.
From what I've read on this forum, these are some improvements which are yet to come to fruition:
- 4tph to Treherbert, Aberdare and Merthyr Tydfil
- 4tph on the City Line
- 4tph to Coryton
- 2tph to Bridgend via Barry
- 4tph to Rhymney
As I understand it, out of these, the ones that have been confirmed are 4tph to Rhymney and the TAM lines.
I assume the extra 2tph to Rhymney will come as an extension of the Bargoed terminators, so these will function as all-stops services to Rhymney. Currently the intermediate stops between Bargoed and Rhymney (Brithdir, Tir-Phil, Pontlottyn) are served northbound by the Bridgend service and southbound by the Barry Island service. Will these calls transfer to the service that will be extended from Bargoed, providing 2tph to both, or will all Rhymney services start calling at these stations (or something else entirely)?
Aberdare and Merthyr are served by a loop route via Cardiff which runs twice an hour. If increasing services to 4tph, will it just be a doubling in frequency of this service?
Bridgend via Barry is currently 1tph which should, in my opinion, certainly be increased at some point. Two of the Bargoed (to be Rhymney) services terminate at Barry Island, with the current Rhymney trains alternating between going to Barry Island and Bridgend, resulting in 1tph to Bridgend and 3tph to Barry Island. Considering only the to-be FLIRT operated routes (so no TAM lines), one potential way of increasing Bridgend services while not running extra 1tph services here and there (and not overserving Rhymney) could be to run 2tph from Coryton.
One to Bridgend and the other to Barry Island to give it a more even 4tph over 3tph. Now I don't know if there's capacity for this but, post Cardiff West upgrade, 6tph (Grangetown-Barry) on a 2-track railway should be possible. This then gives the Coryton line a much-needed 4tph, but there would still be 1 gap in the core valley line network, the City line.
While certainly in speculative territory here (appropriate for the thread, but I still wouldn't want to get too 'crayonista', also I've seen this proposal posted before) one way of filling this gap would be to reinstate a half-hourly Coryton-Radyr service. This could extend to Treherbert to give the Rhondda line 4tph. The key question then is whether the Coryton line can handle 6tph? I assume that without redoubling the answer is no, but if you need redoubling for just 4tph, then at this rate it's probably inevitable that it'll happen at some point.