London has a slightly smaller population than New York City, but it's roughly double the size in geographical area at 607 square miles. So, even with good transport links, trekking across Greater London's 32 boroughs can take a frustrating amount of time.
Riding the Tube from Ealing (lavender in the map below) to Bexley (orange), for instance, could take up to 90 minutes. Enough time to crochet a small hat.
Rainer Lesniewski/Shutterstock
That's why it's helpful to know about a new mapping tool, buried on Transport for London's website, that makes it really easy to visualise London in terms of travel time. We first saw it tweeted by The Guardian's Alex Hern.
The tool, called WebCAT, is built for professional planners in London. But regular people might find it useful, too.
WebCAT lets users create public transport access level (PTAL) maps. PTAL is just a measure of how connected a specific location is to the public transportation network, which includes National Rail, the London Overground, the Tube, the DLR, trams, and buses.
The PTAL value is influenced by the frequency of service at stations and stops and the walking time between stations. A high PTAL value is good - it means there is a high level of connectivity.
Here's what a very zoomed out PTAL map of London looks like. The colour key is below. You can see a large splotch of red (high PTAL) over central London. No surprise - there's lots of transport connections in the city's densest areas. As you move further out from the center, blue and purple (low PTAL) become the dominant colour.
WebCAT can also be used to create maps that show how long it will take to get to or from a specific spot, known as Time Mapping (TIM). This would be especially valuable if you're planning to rent or buy a flat and want to make sure that it's convenient for getting to work, or if your favourite coffee shop is still within walking distance.
Here we've drilled down to an area in east London, with our home base at Westferry station. The colors indicate how long it will take us to travel from the Westferry DLR to whatever's in each little square. The squares each represent 100 meters. Red is a shorter distance (15 to 30 minutes), while blue is a longer distance (more than 75 minutes). It's obvious to see the most inaccessible areas.
Transport for London
WebCAT
The PTAL map is based on all transport modes available in 2011, but what's cool is that it will also forecast PTAL and TIM maps for 2021 and 2031, when London's new underground line, Crossrail, will be up and running.
The anticipation and expected effect of Crossrail - Europe's largest infrastructure project right now - is so huge that other mapping apps have also integrated the new line into their software to predict future travel times.