In this week’s CityMetric podcast, Jonn and I fell out over how many Tube lines there were.

TfL believes there to be 11 – the Bakerloo, Central, Circle, District, Hammersmith & City, Jubilee, Metropolitan, Northern, Piccadilly, Victoria, Waterloo & City lines. 

In my view, there are 14 – those 11 plus the Docklands Light Railway, the London Overground and Thameslink lines. (Keen Skylines listeners will know that I forgot the existence of Thameslink and argued for a mere 13, but that’s by the by.)

In Jonn’s view, there should be 13 lines. Besides the canonical 11, he believes that the District and Northern lines should be treated as four lines, not two.

Now he has written a lengthy piece explaining his thoughts on the number of Tube lines at greater detail. I’ll take those in the reverse order to Jonn, who deals first with his eccentric beliefs about the District and Northern Lines and then onto his view that the DLR, Thameslink and Overground do not count as Tube lines.

To take the Tube lines point first: Jonn’s argument is a good one, but, regrettably, not for the case he wishes to make. He correctly identifies two internally consistent definitions of what constitutes a Tube line. The first, what you might call the “Narrow & Nerdish” definition restricts the meaning of what a Tube line is to the “deep-level” trains, that is, the one that look like Tube.

That definition would restrict the number of Tube lines to seven: the Bakerloo, Central, Jubilee, Northern, Piccadilly, Victoria and Waterloo & City lines. 

This makes sense. These trains can run interchangeably on their routes without modification (mostly – ed.), have the same technical limitations and designs, and look the same. This is a perfectly reasonable definition of the Tube.

The second definition, what you might call the “Generous & Geeky” reading of how many Tube lines there are expands to include a number of routes that are not, strictly speaking, deep-level Tube lines. Under the guise of following this second definition, Jonn defines the Tube lines as the canonical 11, plus his additional District and Northern Lines, on which subject I’ll go into further detail below.

This makes no sense.  Both in terms of its speed, design, capacity and abilities, a Metropolitan, District or Hammersmith & City Line train has more in common with the Thameslink or Overground fleets than the Central Lines. There is no case to count the Metropolitan Line but not Thameslink or the District Line.

You can make a passable case for not including the Docklands Light Railway as it is a different type of rolling stock entirely, but once you have expanded the definition you might as well include the DLR as well.

There are two definitions that work: one that counts only the deep-level lines and one which counts any of the subterranean railways on TfL’s map. Jonn is trying to have his cake and eat it, proving that he who battles Brexiteers must take great care, lest he become a Brexiteer himself.

What about Jonn’s other argument, that the District and Northern Line are not two lines, but four?

Let’s take the case for splitting the District Line first. Here, for reference, is the District Line as it is:

 

Jonn argues that it should be split into two. Let’s call this one the Stephen’s Supreme Line. It’s just a name.

 

Click to expand.

And the second, which would look like this, which we’ll call, for argument’s sake, the Elledge’s Egregious Express Railway:

Click to expand.

The thing about the Egregious Express is it makes sense if you live on the Edgware Road and commute to Wimbledon, or vice versa. But for Jonn’s argument to work, someone living at Wimbledon and working at Westminster would, currently, have to get off at Earl’s Court and change from the Egregious Express to the Stephen Supreme.

But of course, they don’t. They carry on on a regular District Line train. It makes far more sense to think of this route as a series of interweaving branches, rather than a full-fledged line.

(Editor’s note: Stephen seems unaware that trains from Wimbledon run to Edgware Road and Westminster. I put this point to him during the editing process, but he didn’t want to hear it, so I left this in.)

(Further editor’s note: A reader points out that I’d misread Stephen’s original point. He’s right. That’s really annoying. On the upside, I did at least correct his earlier contention that 11+3=13.)

What of the Northern Line? This argument is rather better than the case for two District Lines. In practice, the Northern Line operates almost as two lines now, a divide that TfL expects to formalise. So there is, at a pinch, a case to be made for the number of train lines being seven or 14 – but not the 13 that Jonn believes.

There’s a whole podcast on this if you fancy it.

Stephen Bush is special correspondent at our parent title, the New Statesman. His daily briefing, Morning Call, provides a quick and essential guide to British politics.

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