If you're asking about greenways, here's [1] an article with some pictures. There's an extensive network of bike-able paths throughout the entire city,

If you're asking about pollution, Japanese cars are generally smaller and I believe electric cars are popular there. More trips are also taken by train / bike / moped, reducing overall emissions. Also, the roads + signals seem to be designed well, so there is less stop-and-go traffic.

[1] https://taiken.co/single/tokyo-greenways-the-forgotten-paths...