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Overground
On 18 Sep, 07:17, "
wrote: Charles Ellson wrote: On Thu, 17 Sep 2009 22:34:15 +0100, Charles Ellson wrote: On Thu, 17 Sep 2009 13:21:29 -0700 (PDT), " wrote: MIG wrote: On 17 Sep, 10:15, "Peter Masson" wrote: "Sim" wrote Some differences between Overground and Underground: 1. Third rail electrification rather than fourth, so not compatible for through running. The NLL is 25 kV OHLE between Acton and Camden Road, and between Dalston Kingsland and Stratford, and will be all the way between Acton and Stratford once the NLL refurbishment is complete. The WLL switches from 25 kV OHLE to 3rd rail between North Pole Junction and Shepherds Bush. Goblin remains diesel worked (and if it is electrified it will be 25 kV OHLE. BTW, the Broad Street to Dalston line, most of which is being incorporated into the ELL, was originally 4th rail, but IIRC was converted to 3rd rail before closure. Peter And all electrified parts of the current London Overground were four rail at some point, weren't they? *Ah, maybe not Dalston to Stratford. I believe the stretch from Queens Park to Harrow & Wealdstone is still four rail, otherwise Bakerloo passengers would have to get out and push! It is 3rd rail with the 4th rail bonded to the running rail which carries the traction return current. The LU 4-rail system does not have a deliberate electrical connection between the 3rd/4th rails and the running rails and is only loosely connected to earth/0v to enable control equipment to detect earthing of either electric rail. A further consequence of this arrangement is that trains running over such sections require higher-rated insulation than is necessarily on LU (660v to earth rather than 420v to earth) although IMU all current LU stock ... has been so equipped since the 1960s. I'm afraid all that technical theory stuff just goes over my head. I'm a straightforward, practical sort of person, and as far as I'm concerned, if you count the rails and there are four of them, then there are four rails. *That's just common sense, and no amount of fancy electrical theory is going to change that.- Hide quoted text - - Show quoted text - Now let's be nice to each other! I did not know the details Charles kindly provided, but it does make sense. Interestingly, not only does fourth rail (however wired) exist as far north as Harrow, but the last time I looked there was quite a lot left further on, although some of it was lying rather dismally in the four foot rather than perched on insulators. It was never formally removed, in other words, although doubtless disconnected. On the more general point on whether Overground is part of National Rail, I suggest that it is, behind the scenes, a remarkable compromise/ fudge/whatever. Consider: Overground is a TfL operation, and the concession was awarded to LOROL by TfL. Other posters have already explained the differences between a National Rail franchise and a concession like Overground. Overground is funded and branded by TfL and included in its operations for all public purposes. Overground is, of course, Oyster compatible along with DLR and trams (and buses too, yes). Station specs (staffing, equipment, appearance, branding) have been officially described as comparable with the Underground (although not all the upgrades are done yet). On the other hand, most Overground trains run (or will run) over Network Rail infrastructure, and on some sections they share the line with freight traffic (or the true Underground ). South of New Cross at least, Overground will presumably share its tracks with scheduled National Rail passenger trains, too. One section, though (Dalston Junction west curve to New Cross Gate/New Cross inclusive) is TfL owned/maintained infrastructure. The rolling stock was specified by TfL and is leased by TfL, but is included in the NR Rolling Stock Library as Class 378/x, being yet further variations of the Bombardier Electrostar series (and thus thankfully built in Derby!). Overground is also being treated by the Office of Rail Regulation as part of National Rail: its statistics are included in National Rail Trends just as if it was another franchise. The ORR does not report the figures from other TfL rail systems, any more than it includes Tyne & Wear Metro. And another poster has also rightly pointed out the existence of 25kV in various places, which is why dual-voltage roilling stock is needed. To add a little savour, parts of the 25kV NLL route (Camden Road area?) have third rail as well as OHLE -- a rare combination, I would suggest. If I came across such a compromise system in a foreign capital, I would be intrigued. As it is, it's in London. Hooray! |
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