What city with at least 5million has a train line to airport
Sydney
Tokyo
London
Frankfurt
Singapore
Fill in the blank
So, I was curious to answer this question a bit more in-depth. I started with the Wikipedia page on cities of 5 million or more (which FWIW didn't include Frankfurt, Sydney, or Melbourne - though I added Sydney and Melbourne for my data). Then I researched whether there was an airport train and arbitrarily chose 30 minutes as the cutoff for an express or fast train, with > 30 minutes listed as local train. I also included a separate "Bus Shuttle" category because some airports tout this as a train connection but I find a poor cousin. Note that some cities have multiple categories either due to multiple airports, or multiple train options fitting into different categories.
The data is here:
Airport Trains by City Size (Google Sheets)
I also categorised it by region (somewhat arbitrarily) with the following summary data
| Region | Express Train | Local Train | Bus Shuttle | No Train | Total | %with train |
| Africa | 1 | 0 | 0 | 7 | 8 | 12.5% |
| East Asia | 7 | 18 | 0 | 3 | 25 | 88.0% |
| Europe | 4 | 4 | 2 | 1 | 7 | 85.7% |
| Latin America | 0 | 2 | 1 | 7 | 9 | 22.2% |
| Middle East | 0 | 1 | 0 | 2 | 3 | 33.3% |
| North America | 5 | 5 | 2 | 2 | 10 | 80.0% |
| Oceania | 1 | 0 | 0 | 1 | 2 | 50.0% |
| South Asia | 1 | 3 | 1 | 9 | 12 | 25.0% |
| Southeast Asia | 1 | 3 | 0 | 3 | 7 | 57.1% |
| Grand Total | 20 | 36 | 6 | 35 | 83 | 57.8% |
As might be expected, developing areas such as Africa, Latin America, and South Asia have fewer trains, and East Asia leads. What's surprising is how high North America is, with almost as many express trains as East Asia, despite only 10 cities compared to East Asia's 25. I did notice that while most Chinese cities and many other places are connected by subway/local train, these are often slow with many stops, and are typically supplemented by express buses and taxis for many travellers.
I also note that the list under-represents Europe, probably because definitions of metro areas aren't quite as broad, i.e. Amsterdam, Rotterdam, and The Hague are all separate but a Japanese or Chinese megacity would cover the same land area and be counted as one in the list. Similarly, Frankfurt metro only has 785,000 but the catchment area of FRA airport it would be way larger due to many other populous cities nearby.
TODO: update the doc with the actual subject line here, by adding in fares (and perhaps research the journey time more precisely). I welcome any comments or suggestions.
