Right, the travel-time metric is not compatible with a Euclidean R² metric. You can imagine three subway stations in a triangle loop, such that it's a shorter trip to do a full loop on the subway then to walk to a point in the interior.
There's no way to continuously deform a map so that it represents travel times as distance in a plane.
Oh yes, unfortunately, you can't do this perfectly. There are some graphs that cannot be embedded in Euclidean space in any number of dimensions, e.g. a 4-cycle with distance measured by path length. It's a good-enough approximation for visualization purposes, though.
Not really - you have to wait for the subway, it also takes a finite time to travel, and it frequently stops. It can avoid traffic, but the actual MPH can be slower than a car when you include both those things.
Isn’t the point that you have a way to get to a point far away faster than you can get to a point in between? The worm hole thing ist because you can only exit at discrete points so it pulls a single point far away, and it’s sorrounding, closer to the starting point. That’s probably hard to map to a 2D map because there would be some overlap between the different „islands“ starting from subway stations
There's no way to continuously deform a map so that it represents travel times as distance in a plane.