I think the current service patterns are overall worse than previously, though of course there are winners and losers.
When/if service frequencies increase it will I hope make more sense.
It's particularly poor whenever the Bay line is closed (i.e. much of the time) as that means the extra services from Pontypridd that partly make up for the inconvenience of trains being re-routed via the City Line don't run.
From a operational point of view when the Bay service isn’t running (to Pontypridd) QS runs much smoother, as you remove the conflict across the junction to the south of the station.
When the remodel is complete the “direction” of travel will focus the primary route toward the bay with the line down to central becoming a “branch” how this will ease the current situation or cope with the increased service only time will tell.
QS (Queens Street) at its current location is and will also be hand strung unfortunately, you really need the Radyr and Rhymney lines separated across Newport Road into QS with the coming together of the four tracks before the grade down into Central. Then having if you really have to the Bay service going to Caerphilly or even Ystrad, removing a on the level crossing at QS.
But, that would require massive engineering and cost of a new four track bridge across Newport Road with its space constraints on llandaff side of the road.
Cardiff Central isn’t and wasn’t designed to accommodate terminating services, so you’re forced to terminate services at places like Cardiff Bay which makes sense why they are pushing the TAM services down there vice through to Central.
To be positive for a moment….the current roundabout service from Merthyr to Aberdare and vice versa is working quite well, the only issue is the infamous essentially single line section into Cardiff central across the west junction. The way the service is planned makes this worse unfortunately, booking the Aberdare via platform 7, whilst the Merthyr (waits usually) at Radyr Branch Junc for the Aberdare to pass, then into platform 6.
You could route the Merthyr via platform 4, this would allow the Aberdare to depart simultaneously as the Merthyr arrives. But….you then remove mainline capacity for terminating trains such as GWR ex West Country, Portsmouth and the Cardiff service from Paddington.
The work this Xmas will allow the Aberdare and Merthyr trains to simultaneously arrive / depart from the west with the addition of two new point ends which will allow a Platform 7 to Down Barry Relief (towards Ninian Park), and Up Barry Relief to platform 6.
It’ll allow allow a Up Barry to platform 7, whilst a Canton or UP/DN Barry Relief move into platform 6.
Unfortunately a closing up signal (like those on the west end of platform 6) isn’t being provided in conjunction with the addtional point ends. This would allow a train to occupy platform 7 loading / unloading whilst the next arrival draws up to the signal ready to move into the platform as soon the previous train has left without delay, the same way platform 6 works now.
We need to move away from treating Cardiff Central as a termination station on both sides (mainline and valleys), trains now move through the station at slow speed approaching platforms on single yellow signals, then station staff having to give the signaller a train ready to start signal before the platform starting signal is cleared.
There are also constrains within the signaling equipment that restrict movements which also need to be rectified, they’ll also open up a few extra minutes of improvements and reduce delays.
There really is no need for massive engineering at Cardiff West, minor interventions make a huge difference.