Not commenting on the detail, but to add to the efficiency comment.
It's interesting to note that the Portsmouth - Cardiff service is running (i.e. between terminals) 86.4% of the time in regular daily service - that's 415 minute running out of 480 per 'cycle' of a unit. By contrast, another
FGW▸ service (
SWI» -
CNM» ) on a 240 minute cycle only manages to be on the line between terminals for 134 minutes, and spends 106 minutes sitting in the platform or parked in a siding - running 55.8% of the time, and that strikes me as a bit of an underutilised resource when perhaps the units involved could be earning farebox money
Both services mentioned have an intermediate reversal, and I have INCLUDED the time stopped for that in my "running time". Also included in running time are those extra minutes that seem to get added to the last leg of a trip. 8 minutes from leaving Portsmouth and Southsea to arriving at Portsmouth Harbour is quite generous, when in the other direction you may leave Southsea just 4 minutes after leaving Harbour on many services.