堤防のサイクリンロード: levée cycling roads.
Bike Snob NYC would not approve of the triathlete gear in this video, and neither can I, but it gives you the idea of the bike paths along the levées. Maybe it is time-trail equipment. It still looks asinine. In Japan ten-thousand dollars of cycling gear means these guys are Olympians, or salarymen who I could race hungover. Hard to tell.
Cycling's a lot safer in Japan: largely because the consequences are so high if a driver hits someone. However, most of the cycling here is not enjoyable if you like going fast. The average Japanese cyclist dodders along the sidewalk with a bike that wouldn't be sold in Wal-Mart. It's just a faster form of walking. Nothing wrong with that, and a fine improvement on the charmless automobile suburbs of N. America, but not very challenging. The traffic lights are also quite long and too frequent. Too long for a N. American public to obey.
Why does every major river have huge levées? Well, the economy is driven by construction, but also, Japan is disaster central. I have no idea why they had to come up with Godzilla. In my first year of Japanese we had a two-week unit on the passive voice, and disaster vocabulary: typhoons, tsunami, earthquakes, fires... Notice two of these words come from Japanese?
Cycling in the Japanese mountains is a favourite, when my lungs are up for it and I have the time to get on a train for a couple hours out of Tokyo. The rest of the time, I have the levées (map). The great thing is having up to one-hundred unbroken kilometres to ride on. The bad thing is that there is no cover from the wind. The good thing is you can cheat, use a train, and ride downwind. The bad thing is that you must avoid rush-hour. I'm lucky to live between the Arakawa and Edogawa cycling roads, so I can make a 50km loop of it.
The map link is not perfect: besides being in Japanese it is incomplete. If you suspect there is a cycling road along a levée (there often is) you can now use a satellite view to confirm it, unlike my exploring fifteen years ago living here. It's going to be great when 'Google Maps Bike There' is applied to Japan!