So, last week, the Centre for London think tank published a report called “Turning South London Orange”, which argued that Transport for London (TfL) should take over all suburban rail services in the south of the capital.

This morning, the mayor of London Boris Johnson and the British government’s transport secretary, Patrick McLoughlin, released a joint statement, saying, basically: Okay.

Wow, that happened fast.

Actually the statement goes rather further than that, mentioning services into six different rail terminals. They’re only proposals at this stage – “views are being sought”. Even if it does happen, TfL will only take control of different routes once the various franchise come up for renewal, so the change will take five years or more to take effect.

But this is nonetheless a remarkable statement of intent that the capital’s rail network should be run by the capital’s transport authorities. It’s a big deal.

Here, in no particular order, are some thoughts.

Which lines are we talking about here?

London has 14 main line rail terminals. TfL took over the suburban services into Euston when the London Overground was created in 2007; it swallowed those into Liverpool Street last year, as part of the preparations for Crossrail, and most of the ones into Paddington will follow when that line opens in 2019.

That leaves 11 terminals unaccounted for. Today’s statement mentions six more:

  • London Bridge, Cannon Street, Charing Cross, Victoria, and Waterloo, which between them account for most of the south London rail network;
  • And Moorgate, which accounts for a couple of lines through north London into Hertfordshire.

The statement doesn’t provide a map of all this (boo). But here’s one someone (NERA Consulting) prepared earlier – specifically, in 2011 – which gives you a sense of what we’re talking about here.

Click to expand. Image: NERA Consulting.

If you’ve been counting terminals, you’ll have noticed there are five left unaccounted for. Inner suburban services into two of them – Marylebone and Fenchurch Street – have effectively been in TfL’s hands for years, in the form of the Metropolitan and District lines.

But the other three are a bit harder to explain. The suburban services into St Pancras and Blackfriars stations are served by Thameslink, which is sort of an unloved mini-Crossrail. Those into King’s Cross will get added to the network once the works to expand it complete in 2018. (That programme, incidentally, was originally known as Thameslink 2000. Megalols.)

Today’s announcement contains no suggestion that TfL will take over Thameslink. Hmmmm.

Also unmentioned is the tiny branch line from Paddington to Greenford. No word on what’ll happen there either.

We need more colours

And so to the thing everyone really wants to know: how will this look on the map?

Contra the Centre for London report, it probably won’t mean a sea of orange: it’s already getting difficult to distinguish one London Overground line from another, so the lines will surely have different colours on the map.

But there is a problem that the human eye can only distinguish a limited number of colours without getting confused. You can tell, at a glance, which is the Piccadilly and which the Victoria line. You probably couldn’t do that with three more shades of blue on the map.

There a number of ways around this. The current London rail map uses a sort of candy cane pattern…

…but that’s a bit ugly. Its predecessor used hollow tram lines to show mainline services…

Another option would be to use fainter, pastel colours for the overground lines, as in this amateur map by our old mate, the designer Jug Cerovic.

Click to expand. Image: Jug Cerovic.

This is not going to be an issue for a while, but rest assured that we’re going to be thinking about it. A lot.

What would this mean for the humble commuter?

London Overground has done a very good job of improving services on the north London orbital routes which it’s run since 2007. The routes it took over last year have yet to see any significant change, however.

So what does today’s announcement actually mean for the rest of the network? The spiel promises for the following:

  • more frequent services, more reliable trains, better interchanges and increased capacity;
  • a London Suburban Metro service with the potential for more than 80 per cent of stations to have a train every 15 minutes, up from 67 per cent today, as well as the potential for more regular services via Clapham Junction, South East London and Kent;
  • a better travel environment, and improvements to accessibility and staffing;
  • delivering a seamless and integrated service with joined up travel information.

Some of that is going to require some serious investment: to clean up stations, change signalling, re-arrange track geometry so that you can run more trains without them banging into each other at inopportune moments.

But some of it will just require a different attitude to running a railway. And that, arguably, will be the key difference.

The possible timetable for change, laid out in today’s “prospectus”. Image: TfL/Department for Transport.

When a private rail franchise controls a route, its ultimate goal is to make money for its shareholders: running trains is the means, not the end.

By contrast, when TfL controls a route, its ultimate mission is to run lots of trains to help the city run smoothly. That’s true even when TfL’s role is contract management, and the actual trains are run by a private firm, as happens with the London Overground.

Some London train franchises have a history of cancelling train services at the drop of a hat, just because it’s easier and cheaper than letting them run late. Maybe we’re being utopian, but it’s hard to imagine a TfL-run network doing the same. Even without investment, this would be a big change.

But why bother now?

The press release makes a lot of noises about London’s growing population, the need for more homes and business premises and so on – all of which means we’ll need more railway capacity down the line.

But why is this happening now? Variations on this idea have been floating around for years, and Boris Johnson is under four months from the end of his eight year tenure as mayor. Why propose such a big change, so late in the day?

The obvious reason is politics. Reaction to the news has been almost universally positive, even fom people you’d expect ot be opposed on ideological grounds. Sam Bowman, for example, the executive director of the free market think tank the Adam Smith Institute, just tweeted this:

Which is a mark of how popular this move will be across the political spectrum. While we’re quoting tweets, Conservative party’s candidate to be Johnson’s successor sent this:

The message here is the Conservatives can be trusted to back Londoners against any big businesses that might be making their lives hell. It’s almost as if there’s an election coming up.

Jonn Elledge is the editor of CityMetric and has thought about this way too much.

You can follow him on Twitter here, and like us on Facebook here.