It seems to me that the way cities are laid out makes all the difference. If you have residential streets which do not see much traffic throughout the day, you

It seems to me that the way cities are laid out makes all the difference. If you have residential streets which do not see much traffic throughout the day, you don't need designated play streets. Any good old street with a threshold number of kids living on would automatically transform into one. Necessity drives invention and all that. I've lived and visited several parts of the US, Europe, and India. The major difference seems to be the wide spectrum of city layouts. India—where I grew up—for instance, has a lot of residential streets with houses and apartments. There are also what are traffic streets which act as veins coming out of wider state and national freeways. These intermediate streets take in most traffic which frees up the residential streets and lets the kids play all day/all evening. Big cities in Europe and the US seems to lack this spectrum of traffic streets which results in residential streets themselves seeing a lot of cars and buses plying across. It also perhaps depends on the sports and games culture of the geographical location. For instance, in India cricket is huge. It requires very little space to play a custom game of cricket with rules amended/modified to suit the turf you're playing it on. Same with soccer in a lot of European and South American cities. I don't know how friendly baseball or American football is to the streets.