When I first read this, I was thinking 4G coverage. Is Paris the best in this respect? Most of the lines have full 4G coverage, but I am not sure all do. Funny in the same country in the city of Marseille, there is no coverage at all in the metro.

NYC now has 4G coverage and Wifi in all the stations, but not on the trains themselves. Though that is in the works and will hopefully begin later next year.

Is NYC the biggest or is Tokyo? I love how Google maps now works perfect with the NYC MTA for buses, subway and more. The times are nearly, but not quite represented perfectly. It seems that during the morning, google maps subway times are right on. But not so in the evening rush hours.

An interesting memory from the subway in Santiago, Chile about 20 years ago, they had a type of TV display on the wall of the tunnels that flickered in time to show you a video while the train was in motion. I think that was the first of its kind in the world.

HKG is great in that they have the best payment card. The Octopus card works not only for public transport, but for many types of shopping. And the trains are large and well run.