Watford North Curve in service use (11/12 Jan 2020)

I am quite pleased that I am not working that weekend, because Northwood reversers are not particularly fun. 😅

Less the pressing buttons, more making sure you don’t lock yourself up.

For the uninitiated, Northwood signalling control is based on a push-button panel at Harrow on the Hill cabin. The signalling setup means that to reverse a train via the siding there cannot be another train in the southbound platform. If this happens a wrong-direction move to clear that train out of the platform is generally the only way that you can get things moving again.

If only it was that simple. Whilst in theory you could begin the possession from A773A (Northwood Hills outer home, suitably maintained at danger and temporarily renumbered as PNX773A), you’re then risking a train SPADing that signal and entering the Northwood to Harrow southbound local traction current section, which would be included within the possession within its entirety. Section switches could be opened to single end feed the section if required, but that’s adding additional complexity. As an automatic signal, there’s also additional complexity involved in maintaining that signal at danger.

It’s a lot of additional work and assurance to maintain a safe possession instead of just maintaining JF22 (Northwood southbound starter) at danger, only allowing shunt JF18 to be used, albeit at the expense of the mainline shunt to be a ‘get out’ card.

Joking aside, myself and my colleagues at Harrow are all professionals and, whilst mistakes can happen, specific training is given on the local working of Northwood in situations such as this, with arrangements in place to ensure as much as possible that a train isn’t routed south whilst another is in the siding.

What work are they doing for Chiltern and the Met?

For clarity (for me) the slow line is closed at Harrow, so all trains are running on the fast line. There are trains from Baker Street to Amersham, Chesham and Uxbridge, presumably unable to stop at North Harrow, Pinner, Northwood Hills and Northwood, then there is the Chalfont-Watford-Northwood Hills service which is unable to reverse further south.

Thanks, all clear now!

The videos nicely illustrate the unusual nature of JF21, the wrong road starter. This signal is ordinarily suppressed to avoid being misread, illuminating (as seen) once the first car of a northbound train enter the platform.

A possibly naïve question... Why does the Southbound need to use the siding before reversing and crossing over to the Northbound? Why not just stay on the slow up line?
Thanks

Someone remind me what the flashing light by the right-hand headlight signifies.

Do my ears deceive me, or is there a platform announcement telling customers for Amersham and Chesham to travel to Watford and pick up their service there JUST as a direct Chesham service (well according to its indicated destination) pulls into the platform?

So why would the train be operating with its protection systems isolated for this move?

Ok, perhaps I asked the wrong question. Why is it in RM mode when it's not a CBTC area?

Yes, an important detail I missed. The train will know whether the tripcock should be operational or not (as it were) via the tripcock latch relay, which is activated at the various CBTC boundaries. (It’s also been the cause of many of the defective train issues, but of course we are now getting off topic for this thread).

WD13a in the siding between Hammersmith and Barons Ct only displays its red aspect as the train approaches.

There is also a similar signal but this time an automatic, A382 on the Terminal 4 loop of the Piccadilly Line; this is colloquially known as the pop up signal as if it is due to be at danger it is blank and only displays its red aspect as the train gets closer to it; the reason being that it is on such a long straight section it might encourage train operators to slow down too early and thus limit capacity. You’d be surprised how close red signals look when you’re in the darkness!