“We use WebCAT to provide information on London's transport system to the professional planning community,” explains a rather unpromising page on Transport for London's website. “This connectivity assessment toolkit allows planners to measure public transport access levels (PTAL) and to produce travel time reports.”

I mean, no, that's not exactly doing it for us either, to be honest. You know the voice Steve Coogan uses in The Day Today, when he's a swimming pool supervisor? (“In 1975, no one died. In 1976, no one died...”) That's the voice we're imagining that last sentence in. Try reading it again, but this time, imagine him saying it. In that voice. All nasal and stuff. See?

Anyway. The reason we mention all this is that checking PTAL values and creating time travel maps is just about the most fun thing we’ve seen in weeks.

Let's start by translating this blurb into English. WebCAT stands for “web-based connectivity assement toolkit”. It allows planners to look at maps of particular locations anywhere in London, and see how well connected they are to public transport – something that’s vital, if you're planning new homes or offices.

To do that, it uses two related measures. One is the Public Transport Access Level, or PTAL. That ranks locations on a nine-point scale based on how well connected they are. The best connected places, where you have a choice of high frequency train services and buses, are rated 6b; the worst, where you really might as well walk, are zero. (There are nine points on the scale because values 1 and 6 are both split into two.)

The result of this ranking is this brilliant map:

On the TfL site, you can zoom right into that, and check the transport accessibility of an area as small as 100m square.

That, though, is a fairly blunt instrument. Central Croydon gets a high ranking because it has lots of trains and buses. But it's clearly a bit much to say it's “more convenient” than, say, the Bermondsey riverside, which has a much lower ranking, but from which many people would be able to walk to work.

In other words, PTAL shows where there are good transport links, but it doesn’t show where there are links to.

So, WebCAT also provides another tool: travel time mapping, which does exactly what it says on the tin. It can show you travel times from any point in London as they were in 2011; or you can look into the future, to see how they'll have changed by 2021 or 2031. You can also throw other variables into the mix: time of day, for example, or using step-free modes of transport only.

Using these maps (isochrone maps, to give them the technical name), you can instantly see that CityMetric Towers in London's fashionable Farringdon is – we don’t like to brag – pretty well connected. This map shows average travel times to and from the office in the afternoon rush hour:

Here's travel times from Canary Wharf in the morning rush hour. Unsurprisingly, it's quite well connected to the eastern suburbs, but a pain in the backside to get to or from the west:

That'll change a bit thanks to Crossrail and other initiatives, though. Here's the same map, for 2031. See how the yellow has spread:

Since the Guardian's Alex Hern was nice enough to point us towards this thing, here's a map showing how long it’ll take him to get from his office to everywhere else in London these days:

Our happy hour with WebCAT has taught us one lesson above all others: whatever you do, don't live in the Bromley village of Downe.

All in all, this is really, really cool. Go play.