How long would a (Slough) - Reading - Oxford - Banbury - Leamington Spa - Stratford service take?
End-to-end time was not really the point of the NSE service concept. It was to link the tourist hotspots of London, Oxford and Stratford. But it didn't compare badly with current Chiltern times as their services tend to make a good number of intermediate calls south of Banbury, and I suspect are timed for 75mph to allow a 165 to be used.
With an IEP, the key issue would probably be what speed it was allowed to run at from Hatton to Bearley junction, but if you assume a 50-minute London-Oxford time, plus the 34 minutes Voyagers are allowed Oxford-Leamington, then a sub-two-hour time is do-able, perhaps even a 1hr 50min, if allowed to run at the pace of the non-stop late-night Chiltern service between Stratford and Leamington (a 23-minute timing). Whether Bearley and Claverdon justify calls by London trains anyway, I don't know, but the fact is people are far more likely to want to go to Birmingham from those places and are now well-served by the LM service via Solihull.
As for service levels, the simple fact is that there are insufficient people travelling from London to Stratford by train to warrant an enhanced service. Chiltern trialled additional services during the Summer a few years back, as well as additional late night "theatre trains", but they obviously didn't result in an increase in ridership or they would have been retained.
Yes, having to change trains is inconvenient, but even in the current timetable it's often quicker to change at Solihull (even allowing for the ~30 minute wait there) than to wait for the next direct train from Marylebone, and if you include the option of local buses or taxis from Leamington Spa or Warwick, that gives further journey opportunities.
Whilst it would be nice to have a good frequency of direct trains to just about anywhere, there are only a finite number of units, drivers and guards to go around, so a TOC has to plan to make the best use of them.
Who said anything about an enhanced service?
What there is now would be fine, if only it got some promotion - of the kind NSE most certainly used to do, but as I said, Chiltern's timetables are always tagged Birmingham and Kidderminster - never a mention of Stratford.
Did you actually read any of what I said about tourists' travel habits or about the rationale for this service being launched in the first place in the early 1990s? Before then the railways took no interest whatever in the potential of Stratford to generate traffic and revenue in this way. Chiltern seem hell-bent on turning back the clock in pursuit of commuter gold from the West Midlands and Oxfordshire. You may be fine travelling with your myriad connections, taxis, etc, etc. Your average tourist, laden with heavy suitcases, may beg to differ.
IIRC service frequency on the main line was considerably less, and NSE ran their trains in marginal time. So it's not strictly comparable.
I would have thought that one or two marginal time workings would be worth it - but at what times is there a significant demand?
Yes, NSE did run most of their trains in marginal time, because that's when tourists are most likely to be travelling. How many people on holiday want to leap out of bed and travel in the peak, when they do that anyway the rest of the year?
But NSE also ran a lot more trains north of Oxford than FGW does now, because until 2003 there was only one XC train per hour south of Birmingham, so there were more NSE/Thames trains running to/from Banbury to be extended into Warwickshire.
FGW's train planners are highly skilled at making the best use of their rolling stock and probably have a draft timetable tucked away somewhere already. As I said above, it's not about huge numbers of through trains, it's about a carefully timetabled selection of them, backed up with proper marketing.
According to Wikipedia, the population of Islip at the 2001 census was 617. Hardly a massive market, especially as it's a poor railhead for surrounding areas compared to Oxford Parkway which is much better connected by road.
And, given congestion on the existing Oxford route, and the large population north of Oxford, it's difficult to argue that the new service doesn't offer something useful.
Don't get me wrong, I think the proposed timetable has its flaws, but some of the arguments here are marginal at best.
You clearly don't understand the issue about Islip. It has nothing to do with it being a railhead. It's about providing a quick link for the locals into central Oxford, which the buses can never do because of the congestion - and it remains to be seen how the roads handle the impact of Parkway. Being the Oxford area, it probably won't be good news.
The people of Islip are not crying out for an hourly train to Marylebone, if that's what you think. Footfall in 2007-8 before the enhanced Bicester branch timetable was introduced was 14,240. It rose to 29,126 in 2011-12 with the extra calls, and they weren't going to Bicester. The issue is providing a decent enough frequency, across the day, to make the train a practical travel option into and out of Oxford. A four-hour gap in a timetable, at whatever point in the day, or just one morning peak-time train into Oxford, means it will not be, with the inevitable impact on use of the station and the railway more generally.
Indeed, Chiltern will make the killing from Oxford Parkway due to its location and road links, not from Oxford itself. As has been mentioned plenty of times before there is a massive untapped market there who dont want to suffer the nightmare that central Oxford is for cars.
A massive untapped market? Hardly. Lots of people who drive from Kidlington to Bicester North will switch to Parkway, so not exactly an untapped market. One of Chiltern's targets is people who already go to London but use the M40 coaches as it's easier to get to Thornhill park-and-ride than the station from much of the city, so a market already tapped by Stagecoach and Go-Ahead, and there is, of course, the Cotswold Line, which is a market tapped by FGW (barely a year after opening the 190-space car park extension at Hanborough often has 150-plus cars in it on weekdays) but an area where Chiltern will no doubt run one of their dubious marketing campaigns in a year's time - 90 minutes to Birmingham ring any bells?