TfL has a tool that lets you map travel times to anywhere in London, and it is brilliant

This one shows travel times to Soho. Image: TfL/WebCAT/Google Maps.

“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.

 
 
 
 

Tackling toxic air in our cities is also a matter of social justice

Oh, lovely. Image: Getty.

Clean Air Zones are often dismissed by critics as socially unfair. The thinking goes that charging older and more polluting private cars will disproportionately impact lower income households who cannot afford expensive cleaner alternatives such as electric vehicles.

But this argument doesn’t consider who is most affected by polluted air. When comparing the latest deprivation data to nitrogen dioxide background concentration data, the relationship is clear: the most polluted areas are also disproportionately poorer.

In UK cities, 16 per cent of people living in the most polluted areas also live in one of the top 10 per cent most deprived neighbourhoods, against 2 per cent who live in the least deprived areas.

The graph below shows the average background concentration of NO2 compared against neighbourhoods ranked by deprivation. For all English cities in aggregate, pollution levels rise as neighbourhoods become more deprived (although interestingly this pattern doesn’t hold for more rural areas).

Average NO2 concentration and deprivation levels. Source: IMD, MHCLG (2019); background mapping for local authorities, Defra (2019).

The graph also shows the cities in which the gap in pollution concentration between the most and the least deprived areas is the highest, which includes some of the UK’s largest urban areas.  In Sheffield, Leeds and Birmingham, there is a respective 46, 42 and 33 per cent difference in NO2 concentration between the poorest and the wealthiest areas – almost double the national urban average gap, at around 26 per cent.

One possible explanation for these inequalities in exposure to toxic air is that low-income people are more likely to live near busy roads. Our data on roadside pollution suggests that, in London, 50 per cent of roads located in the most deprived areas are above legal limits, against 4 per cent in the least deprived. In a number of large cities (Birmingham, Manchester, Sheffield), none of the roads located in the least deprived areas are estimated to be breaching legal limits.

This has a knock-on impact on health. Poor quality air is known to cause health issues such as cardiovascular disease, lung cancer and asthma. Given the particularly poor quality of air in deprived areas, this is likely to contribute to the gap in health and life expectancy inequalities as well as economic ones between neighbourhoods.


The financial impact of policies such as clean air zones on poorer people is a valid concern. But it is not a justifiable reason for inaction. Mitigating policies such as scrappage schemes, which have been put in place in London, can deal with the former concern while still targeting an issue that disproportionately affects the poor.

As the Centre for Cities’ Cities Outlook report showed, people are dying across the country as a result of the air that they breathe. Clean air zones are one of a number of policies that cities can use to help reduce this, with benefits for their poorer residents in particular.

Valentine Quinio is a researcher at the Centre for Cities, on whose blog this post first appeared.