Referring to earlier posts in this thread I should like to make some general points about the Old Oak Common (OOC) station as there seems to some misconception about the original justification for this station.
It was initially foreseen that Crossrail 2, with a large station serving Euston / St. Pancras / Kings Cross, would be open in time for the completion of HS2. It was clear that the passenger flows arising from up to seventeen 400m long HS2 trains arriving every hour at Euston would have overloaded the local distribution network as it now stands of Underground, buses and taxis — significant additional capacity was needed.
When it became clear that Crossrail 2 was not going to happen in the required timescale the station at Old Oak Common was proposed to remove some 30% of the passengers from HS2 before the trains reached Euston and distribute these passengers through central London using Crossrail.
In addition to the original idea of an HS2 to Crossrail link for London bound passengers, it transpired that this station would become an alternative to the originally promoted direct connection of HS2 to Heathrow airport by either a deviation of the route or by the construction of a dedicated spur. Passengers would be able to transfer to and from Crossrail from HS2 with frequent connections to the airport so there would be no time loss on the main route and there would be no need to run standard length HS2 trains to a variety of destinations from Birmingham northwards with a commercially unattractive frequency to each of them. The station at OOC would also enable a simple connection between the Thames Valley suburban stations out to about Reading and all those areas to be served by HS2.
Platforms would be necessary on both the Relief and Main lines at OOC to allow for the closure of a pair of them for maintenance with the result that this interchange also became of interest to HS2 in its quest for more passenger to fill the enormous capacity it was creating. It was promoted that journeys from and to the West Country, Bristol and South Wales to Manchester and Leeds would potentially be faster via OOC than the traditional routes by stopping all GW Main Line services at OOC. However because of the intensity of services on the Great Western double sided platforms would be needed and so what started out as a simple interchange became a monster.
All this may or may not have made sense — I personally feel that it was all a ploy to fill HS2 seats rather than concern for the greater good of passengers on the Great Western. The ORR has recently published ‘Origin and Destination’ data based on ticket sales and although one can see that there are flows from places like Exeter and Plymouth to Manchester and Leeds the numbers are dwarfed by the flows to London. These data were not in the public domain when the debate was at its height but they do now call into question the decision to spend huge amounts of money on building a large showpiece station to serve the size of the traffic flows.
And now of course the completion of HS2 past Birmingham has been pushed so far into the future that for all practical purposes it can be ignored and both the number of HS2 trains serving OOC and the time savings to Manchester, Leeds and the rest have been reduced significantly. Any original commercial reason that there may have been in stopping all the GW main line trains at OOC has now gone.
Like many other large projects undertaken by various governments it seems that there has been no clear, consistent reason for the construction of the station at OOC. The reasons change with the seasons and various levels of mission creep can be seen here. So basically what I am saying is that the HS2 to Crossrail/Elizabeth line interchange still makes sense — less so now that the HS2 route and numbers of trains have been cut back — but the HS2 to GW Main Line interchange for all GW trains now makes little or no sense at all. It always was the case of the tail wagging the dog.
