Suginami Kotsu-Kōen, or Suginami Children's Traffic Park, consists of a network of roads complete with road markings, traffic lights, road signs and railway crossings where children can cycle while observing the rules of the road. That's right, all those rules and regulations that frustrate us adult cyclists are just what children are looking for to add some structure and learning to their play.
While the major intersections of the course are manned by voluntary staff who occasionally remind children of the rules, there is not an overbearing traffic-nazi presence. For the most part everyone is expected to ride on the left, and respect the traffic lights, but don't rely on an 8 year old to show much interest at stopping at a stop sign. Helmets are also not mandatory, but can be borrowed on request.
Just outside the park is the Zenpukuji Cycling Route, a 2,400m circuit along the banks of the Zenpukuji River and through sections of Wadabori Kōen. After borrowing a bicycle from Kotsu Kōen you're also free to ride this longer route, although you're sharing it with joggers, other cyclists and the general walking public.
In addition to cycling facilities, Kotsu Kōen includes a number of playgrounds with jungle gyms, swings, slides, sandpits and even a decommissioned D-51 steam locomotive. On summer days there is ample shade provided by the trees and a large fountain does a great job of keeping the area nice and cool. The park is dotted with many picnic tables, and has toilet facilities, making it perfect for an afternoon picnic with the family.
The Suginami Children's Traffic park (杉並児童交通公園) is located 12 minutes walk north of Hamadayama Station on the Keio Inokashira line, and is open daily from 9am to 4:30pm.