London's public transport is great. It lets you go pretty much anywhere via a seamless combination of buses, trains and even the occasional ferry.

It's less great, though, if you aren't able to get on any of it in the first place. Much of London's Underground system is old, and deep under the ground; this, if you're a wheelchair user or are otherwise restricted in your movement, is not good news.

Buses are a lot better: most can crank down to the level of the pavement, and there are designated spots where you can park your chair on board. But in a city the size of London, buses aren't really enough.

TfL released its latest "step-free guide" to the London Underground in 2015, and it basically does what it says on the tin: it shows those stations without big flights of non-escalator staircases, which would pose a problem for anyone in a wheelchair or others with mobility issues.TfL greys out the unusable stations, but we've erased them in the map below to make things a bit clearer:

Click on image to see a larger size. Image: TfL, modified by CityMetric.

If you squint, it all looks prety straighforward: loads of stations have disappeared, but you can still take a fair few on the District and Circle lines, plus a good chunk fo the Overground and the whole DLR. Most of central London is off the cards, unless you happen to be travelling from Ealing Broadway to Oxford Circus (lucky you!).

But all those coloured symbols on the map mean different things for your ability to access trains at that station. Just because a station doesn't have a flight of stairs, doesn't mean there aren't other things standing in your way.

An "R" in a green box means you need to call ahead to get a ramp set up.

The green and red circles indicate the gap between train and platform (more on that later).

Little red notes and exclamation points indicate stations where certain interchanges do involve stairs, or where you have to access the station through a certain entrance to avoid them.

The map actually comes with all this supplementary material, explaining certain stations' quirks: mini flights of stairs, say, or stairlifts which will carry your manual wheelchair, but not a motorised one:

Essentially: planning Tube journey when you have reduced mobility is a bit like running a small military operation.You need to research every leg of the journey beforehand, and probably need to call ahead, especially as TfL advises that you check the lifts are running if you need them. (To its credit, TfL does provide taxis if lifts are out of order.)

If you're in a wheelchair and can't do escalators, the map gets even simpler – and your journey gets even more complicated.

This map shows all the stations which have lift service (they're marked by a blue ring around a green circle), or stations where the platform is level with the street (green ring around a green circle). It's taken from TfL's "Avoiding Stairs" guide, but we've removed the stations which only have escalator service:

More caveats:

Notes in red indicate where this only applies to one direction.

Stations still on the map but with an open circle mean you can interchange, but not exit or enter the station.

Little numbers inside the circle mean there are that there are a handful of steps along your route in the station.

An exclamation mark means you need to check the supplementary material for more information.

I thought about redrawing the map with just the stations which have straightforwad, full access for wheelchair users, but I'm not sure it'd look like much of a map.

One last one: those letters on stations indicate the gap you need to bridge between the platform and train. A green "A" means TfL reckons wheelchair users shouldn't have any trouble getting across it: the gap is less than 50mm high and less than 85mm wide.

This map shows only those station with this designation, or where station staff can set up a ramp:

If you were a wheelchair user who needed to use a lift, and wasn't confident of bridging larger gaps to board trains, you'd need to cross-reference the above two maps (whose information is provided separately by TfL) to figure out if your journey is plausible. Spoiler alert: for most journeys on the Underground, it probably isn't.

We're much better off than Paris – we wrote last June about the fact that the map for wheelchair users there is basically a single line – but accesibility in newer networks around the world, like those in many Asian cities, leave ours in their dust. Our network may be old and difficult to upgrade, but what use is public transport if a chunk of the public can't actually get on it?

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