I support the idea of building infrastructure to a timetable, but if that timetable isnt correct for the current/potential demand, then it’s a waste. Areas of extra track have to be as useful as possible, so having as many trains on them as possible and multiple stops helps. This is why (South) Ruislip to Denham (Golf Club) makes sense to me. Frequent stoppers (I would hope) and multiple stations on this stretch.
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Chiltern timetable - what if it wasn't about Brum-London?
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Chicken / Egg.
Putting infrastructure simply based on where it happens to fit doesn't always mean a coherent or efficient timetable can be planned upon it.
But would it really ?
The problem with loops at all stations is you'll end up slowing the stoppers down too much whilst trying to force fasts through - i.e. a fast from Marylebone is timed to get past South Ruislip, West Ruislip and Denham in about 3 mins whereas a stopper takes 4 mins between South and West Ruislip and 4 mins between West Ruislip and Denham.
Having loops at every station probably wouldn't add that much usable capacity.
The Planner
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It wouldn't, people need to understand that platform loops don't really give you anything. You would be approached controlled in for a start which will add at least a minute then you are waiting for the following train to pass. Any train being overtaken it going to be sat for at least 5 minutes.
Bletchleyite
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That may or may not be a problem, depending what you are trying to achieve with that train.
Platform loops are widely used in mainland Europe so are clearly not completely pointless. There are/were even some examples in the UK, such as the Poole stopper being looped at Brockenhurst.
They tend to work when the total level of traffic on the line is relatively low - say 2 stoppers per hour with 2 fast trains, or so. Particularly if it is "mid route" so the number of passengers inconvenienced by the extended stop is minimised.
A good UK example is the loops on the West Anglia Main Line, where the trains put 'inside have relatively few passengerson by that point (at Broxbourne or Harlow)
For higher levels of services, they seldom don't achieve anything better than a well-flighted timetable does.
Bletchleyite
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Yes, that's fair. A place it'd be handy to have them is the CLC line at Warrington Central which operates precisely the pattern you describe - the fact the stoppers are being lopped up is precisely because it doesn't and there's not really anywhere to put some as the station is up on an embankment.
Your real ideal in a "2 fast 2 slow" type scenario is to have two island platforms with the loops at the sides and the through lines in the middle, allowing perfect connections. You then want a several-minute stop for effective interchange in both directions. That's referring back to what I say on these threads about designing the infrastructure for the service.
I don't think that's really needed for Chiltern, though, as you don't really need a fast Brum and a slow Brum, because it's more about going to London (or to a lesser extent Brum commuters past Banbury) it's more about the classic South East pattern of "fast to X then all stops to Y" that you need, and that sort of pattern lends itself very well to flighting 2-4 half hourly services on a double track line.
A quad section from South Ruislip to beyond Denham is not a platform loop, it's several miles of four track. And if a service calls at all three, I would think a fast could overtake if running at line-speed down the centre tracks. Possibly two if a 3 min headway.
Beaconsfield would be this, and arguably less useful. A faster service could run at higher speed, rather than slowing to run by the platform. Better to quad from there to Wymcombe.
Gerrards Cross has terminators so there is more case for something to enable overtaking once a terminating service has arrived.
I do agree that this isn't the first thing needed on Chiltern. And the longest trains are not being run. If they had wires and new trains, that would bring a lot more growth and benefits than a few loops or quad sections.
Beaconsfield would be this, and arguably less useful. A faster service could run at higher speed, rather than slowing to run by the platform. Better to quad from there to Wymcombe.
Gerrards Cross has terminators so there is more case for something to enable overtaking once a terminating service has arrived.
I do agree that this isn't the first thing needed on Chiltern. And the longest trains are not being run. If they had wires and new trains, that would bring a lot more growth and benefits than a few loops or quad sections.
It's less than "several" - 5 would be closer (Sth Ruislip - Denham) - and at it's unlikely to be demand for more than 2tph at Denham, Ruislip etc. which means flighting them to run behind the fasts to Oxford or Birmingham means they aren't caught up by the next ones until they are nearing Gerrards X.
There's a turnback siding at Gerrards X which means the terminators can get out of the way of the fasts coming up behind them from Marylebone and return pathed behind southbound fasts. AIUI the problem with extending these to Wycombe is lack of platform availability at Wycombe ?
Bletchleyite
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Wycombe has a south facing bay.
I'm aware of that - but it was something mentioned on here that a second bay would be needed if the stopper went to 2tph - presumably it's because the current Wycombe terminator arrives at xx.55 and doesn't leave until xx.19 - which means an opposite clockface one would be arriving at xx.25 - which might be a bit tight ?
I think it's fair that this whole conversation assumes a new timetable. That's a pretty long layover.
I wonder if 3tph is a better aspiration - given the other point about the flights in the short quad section. Btw I think 5 is fair for "several" but it's subjective. Also, 3tph is a reasonable frequency for an outer metro service. 2tph is not.
And then we have three flights per hour, if we think that is possible - rolling to a 20 min timetable:
1 fast (Birmingham)
1 fast/semi (Oxford / Stratford)
1 semi (Aylesbury / Banbury / an Oxford slow pattern?)
1 stopper to High Wycombe (some to skip smaller stops)
x 3
leaving the Amersham route to one side.
3tph for an outer metro *might* be suitable depending on the places served.
In that respect the Wycombe stopper is probably more akin to the Hertford N / Stevenage service - Wycombe & Stevenage are both large places, Gerrards X, Beaconsfield and Denham are more like Hertford and Cuffley.
Most of the stations within London have better services from tube lines in close proximity.
I'm not sure there is the demand for a stopper on the Chiltern lines in the way there is on the WCML or GWML for example.
I agree with that. These are sleepy, very peak-focused markets and I can't see the level of off peak or reverse-commuting that the likes of Watford, Slough, Reading and MKC receive.
Wycombe is much less of a jobs market than even Stevenage too, although it is larger. Stevenage is a junction and railhead for the north too. Wycombe has the odd Birmingham service but not quite the same.
Jamiescott1
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It used to be 2 tph prior to the siding at gx being built
But wasn't that tied up with the pre-Evergreen timetable ? So Wycombe, Gerrards X and Beaconsfield got a service which was no worse, and if anything was better than before that ?
They used to get more regular fast calls. I reckon an electric service making 1-2 stops after Beaconsfield to London would have roughly the same time as a diesel non-stop today - newer nicer trains would help sugar the pill too, if B/GX were removed from some faster services but given the 3tph.
HSTEd
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Is there any serious discussion going on about that proposed NNML terminus at Old Oak Common?
That could change things dramatically.
That could change things dramatically.
The Planner
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Aspirational, nothing in concrete yet.
Not sure if anything’s concrete but I imagine there’ll be provision for it. If not, then I’d expect that a huge mistake is being made.
HSTEd
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Well its just that combined with what appear to be through lines at both of the Ruislip stations on the Chiltern side might allow many of the timetabling issues we are talking to dissapear.
We could have a pattern out of Marylebone which is all shacks to High Wycombe, then run a Birmingham/Oxford OOC service that is nonstop to Gerards Cross, High Wycombe and then all shacks to their destination.
There appears to be for at least one through line at Denham and for two at Beaconsfield.
Chances are you aren't going to have a train stopping in both platforms at the station and simultaneously want fasts to cross in both directions, so three tracks is probably rather useful.
4tph High Wycombe, 2tph Oxford and 2tph Birmingham/Beyond.
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That is ostensibly a lower service than today. You aren't serving Aylesbury or Stratford (which is the Banbury semi in off hours). Oxford can handle another frequency too, arguably a more semi/slower service - especially if we are using the HW bay more heavily.
adrock1976
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Aylesbury is already served by trains that run via Harrow-on-the-Hill, unless you are referring to the route via High Wycombe.
Ideally, with some double track to make a dynamic loop between the vicinity of Monks Risborough and Little Kimble, a 30 minute frequency shuttle can run between Aylesbury and Princes Risborough.
Regarding Stratford upon Avon, the GWR Oxford terminators (not the Cotswold opposite half hour, but the other two) could be extended to Banbury, which would avoid having so many passengers ramming onto the Intercity XC for the short run, plus as ICXC have not called at Didcot Parkway for a good number of years, this would also help in reducing overcrowding on the XC at Oxford General [sic] as intending passengers would not have to change. Furthermore, a Banbury terminator could be extended every 2 hours to Stratford upon Avon, or improve the Leamington - Stratford upon Avon service frequency (can be slightly tricky due to the single track between Hatton and Bearley Junction).
Also, I have designed a post HS2 Chiltern Taktplan, which is in a separate thread at https://www.railforums.co.uk/threads/suggestion-chiltern-clock-face-timetable-post-hs2.214031/
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