On Saturday, April 9, 2005, I entered the park via the north entrance, crossing the bridge over the moat close to the Takebashi subway station.
As I crossed the bridge with my family, an elderly Japanese gentleman [...] produced a handful of plastic cards. He offered one to each of us, pausing briefly to decide whether my three-month-old daughter strapped to my chest required a card. He decided she did and handed me two cards. He said nothing, and, as my Japanese is limited, I offered no conversation. We walked on into the gardens to look for a spot to enjoy our family picnic. Two hours later [...] we packed up our picnic things and headed towards the exit at the East Gate at Otemachi. As we approached the exit, we joined a line of people in front of a small kiosk. As the line shuffled forward I saw people returning their plastic entrance cards. I fished around in my pocket and retrieved the cards I'd been given. [...] I slid my plastic cards across the countertop [of the kiosk] through the hole in the glass [screen, to the Japanese lady inside]. The lady took them [...] and stacked them in a rack with others. She bowed her head slightly and thanked me with a smile. No money changed hands. No explanation was given for why I'd been carrying around two white plastic admission cards since entering the park two hours earlier.
What was going on with these admission tickets? Why bother to issue a ticket if no fee was charged? [...] I realized then that the Imperial Palace Gardens was using a kanban system!
In the Imperial Palace Gardens, the gardens themselves are the system: The visitors are the work-in-progress, and the capacity is limited by the number of admission cards in circulation. Newly arriving visitors gain admission only when there are available tickets to hand out. On a normal day this is never an issue. However. on busy days, such as a holiday or a Saturday during cherry-blossom season, the park is popular. When all the admission tickets are given out, new visitors must queue outside across the bridge and wait for cards to be recycled from visitors as they leave. The kanban system provides a simple, cheap, and easily implemented method for controlling the size of the crowd by limiting the number of people inside the park. This allows the park wardens to maintain the gardens in good condition and avoid damage caused by too much foot traffic and overcrowding.
-- David J. Anderson
Quoted on Tue Jul 24th, 2012