Marcel Yuwono 11 July 2020
Motivation
A while back, I stumbled upon 45 Minute Cities, in Professor Alasdair Rae's blog. He generated isochrones of different cities in the UK to see how far 45 minutes will get you from the center of a city. I thought these maps looked beautiful, and decided to spin up some of my own maps to visualize how efficient public transport systems in major cities compare to each other.
So what's an isochrone anyway?
To put it simply, an isochrone curve is a curve generated from an origin, such that each point in the curve denotes equal travel time from the origin to that point. An isochrone map, is then an area of points which can be reached within some amount of time from the origin.
Isochrone maps are used extensively in urban planning and analysis, by hospitals to visualize the area which their ambulances can reach in 5 minutes, or by restaurants to see which customers live close enough for pizza delivery. Let's take a look at how they can be used to calculate the efficiency of mass transport systems.
Methodology
I used the TravelTime API to create 30-minute isochrones by public transport only. The start time is standardized to be Friday, 7/10/2020 at 7 AM, a common time when people depart for work. Then I used QGIS to frame and mask the polygons before moving on to Adobe Illustrator to stylize the finishing touches.
I combed through different listicles to see which cities had the best public transport systems and selected a few to map. Then, within each city, I selected a major transit station that best fit these 2 criteria:
- High passenger traffic
- Close to the centroid of the city
Most sources, in deciding the "best" systems include different criteria such as
cleanliness and comfort, but today, we're only concerned about distance and time. The idea is
that the most efficiently placed stations are those that can reach the largest area in a
set amount of time. To do this, we map a 30-minute public transit isochrone from the stations,
then calculate the area of the isochrone map.
Let's take a look at the results, from lowest to highest coverage.
Click each map to access a high-res version of the image.
Gare de Lyon
Located in Paris by the Seine, Gare de Lyon serves over 90 million passengers annually, serving both long-distance track and regional railways. The station was opened in 1849 for the 1900 World Expo.
Berlin Central Station
With 16 tracks and 7 platforms, Berlin Hauptbahnhof serves 1,800 trains and around 350,000 passengers every day. Services include the S-Bahn, U-Bahn, trams and long distance trains.
Copenhagen Central Station
The largest railway station in Denmark, Copenhagen Central Station was built in 1847 and serves over 38 million passengers every year. It serves the Copenhagen Metro, S-Train, and the Danske Statsbaner trains.
Waterloo Station
Founded in 1848, Waterloo station is the busiest station in the UK, serving over a hundred million passengers with 24 platforms. The station serves the South Western Main Line and the West of England Main Line.
Grand Central Station
One of the most iconic stations in the heart of New York, Grand Central serves 67 million passengers every year with a staggering 44 platforms and 67 tracks—the most at any station in the world. "Grand Central Station" is actually a misnomer, its official name is "Grand Central Terminal."
Dhoby Ghaut Station
Located at Orchard Road in Singapore, this MRT station is the only station in the city to connect three different metro lines: the North-South line, the North-East line, and the Circle line.
Tokyo Station
Tokyo station serves 4,000 trains daily and 500,000 daily passengers in perhaps one of the most intricate mass transit systems in the world. The station serves many different lines such as the "Shinkansen" bullet trains, the JR Central lines, and the Tokyo Metro.
Final Thoughts
Isochrone maps are one way to visualize public transit efficiency, but we should be careful not to draw any conclusions solely based on this data. Different cities have different public transport needs. While wider sprawls might need greater coverage, smaller cities can be adequately served by a smaller system.
Next Steps
How much population do these systems cover? What if we map larger, 1-hour, 2-hour or even 3-hour isochrones? 30-minute maps are disadvantageous to long-distance trains, since it often takes more than 30 minutes from one station to another. They pick up speed towards the middle, and have a long-term payoff.
The TravelTime API didn't have data for several countries that I wanted to visit, including China and South Korea. The data for existing cities are also incomplete, and can produce inaccurate results. OpenRouteService has a free isochrone API, but not for public transport. There's nothing much I can do at the moment without writing my own isochrone library, which might be a future idea.
References