As a new forum member and also a regular user of the Pompey-Cardiff service, I simply cant resist replying to this thread, with a slightly more realistic proposal which wouldnt involve use of 180s (hint: put them on Manchester-Glasgow/Edinburgh!) and wouldnt require vast extra resources to improve the route!
I agree with the posters who think FGW should withdraw from Brighton- I've thought this for several years now. Whilst I am sure it does not make commercial sense for FGW to withdraw (ORCATS raids etc), the stock used on Brighton services could be put to better use elsewhere on FGW routes as has been pointed out throughout the thread.
I have not looked into the exact diagramming for these services but a quick review of the timetable would suggest (perhaps with some creativity on the part of FGW) that axing Brighton services could release two 158 units for other uses.
What to do with these trains? Well, two units could admittedly be very handy for providing a two-hourly Salisbury-Swindon via Melksham service, say. This is certainly one option which should not be disregarded, but would bring with it extra staff costs, marketing costs, etc. Yes, these costs are relatively small, but we are now in an age of public sector austerity where really only the cheapest options will be acceptable to decisionmakers. Also, in my opinion, a route, at least between urban centres, isnt likely to attract car users (or even bus users) unless it has an hourly or better frequency, and you cant do this between Swindon and Salisbury with only two units!
As has rightly been pointed out, there is a lot of pressure on the Portsmouth-Cardiff route. The overcrowding problem is worst between Southampton and Bristol. The existing 3 car 158s seem to cope fine between Portsmouth & Southampton (busy but not standing,even in the peaks) and also Bristol-Cardiff.
So to me, the ideal use of 2x 158s is to use them to strengthen Portsmouth-Cardiff services between (ideally) Southampton and Bristol, or, between Salisbury & Bristol if splitting & joining of carriages at Southampton Central is too difficult 9see later in my reply).
This might (just) be possible to do using the existing timetable PMH-CDF with a few tweaks. At the Bristol end, services on the regular interval timetable arrive at xx48 from Portsmouth, and depart to Portsmouth at xx23. As trains reverse at Bristol, there is a station stop of several minutes for drivers to change end etc, during which time a split/join operation could be done without significant detriment to the existing timetable. Platform occupancy at Bristol does not seem to be an issue (some platforms seem to only be used once every few hours!) so leaving a unit on a platform for 35 minutes between journeys is probably not a problem.
At the Southampton end, things would be much more difficult- services to Portsmouth arrive at xx04, whilst trains northbound leave at xx10. This 6 minute turnaround is clearly not sufficient to detach a unit, have the southbound service go forward to Portsmouth, and then have the northbound service arrive and attach, let alone be robust in the event of late running.
However my observations of the Southampton-Bristol ops suggest that station dwell times are extended due to overcrowing and slow boarding/alighting from 158s not enough doors to handle all the people! By operating 5 car trains on the core section, it might be possible to trim a minute from dwell times at Bath, Trowbridge, Warminster, Salisbury and improve reliability/ reduce recovery time. Throw in some timetabling sleight of hand (or dare I say it, axe a stop) and I reckon you could save enough time each way to enable perhaps a 12 or 15 minute turnaround at Southampton for the extra unit, which might be enough.
Of course there are other problems at Soton Ctl including high platform occupancy and a regular tendency for knock-on delays (not enough platforms, and the tunnel doesnt help) . It might not be possible to do such splits/ joins at Southampton, in which case I guess strengthening between Salisbury & Bristol would be the way forward.
A quick play with the existing timetable shows that on the hourly interval timetable, about half of all Portsmouth-Cardiff trains on the regulr hourly interval could strengthened between Southampton and Bristol. I've not done the maths for Salisbury, but probably 2/3 of trains could become 5 cars Salisbry-Bristol.
Although there woul;d be challenges to address with this arrangement, the advantages as I see it are:
- Use of the split/join capability of DMUs
- No extra staffing costs
- Extra capacity (more than a 180 could provide!) where its really needed, ie Bristol-Southampton
- Using resources to support an existing market with proven suppressed demand, rather than on some commercially risky and operationally difficult extra service which the DfT simply wouldnt approve inour current dire economic straits
Regarding Southampton-Brighton services, this corridor is sees an OK service from Southern nowadays, so the importance of the FGW services is much less than it once was. The AM Portsmouth-Brighton FGW service is noted in the Sussex RUS as struggling to provide capacity between Worthing and Brighton.
To replace this, Southern could probably provide an AM Portsmouth-Brighton train (probably a 3 or 4 car 377) through diagramming changes alone.
As far as use of 180s on Portsmouth-Cardiff are concerned, well the route doesnt have the linespeed or characteristics to really justify their use.....though in an ideal world I would love to see them at Southampton Central!
Jeez, I never intended that reply to become such an essay!