If you have a chance to start a Shinkansen trip at Tokyo station, I’d recommend to get to the platform 30 minutes before the departure and line up at the head of the line to watch an incredible show.
A Shinkansen arrives and unloads the passengers, then it has 20 minutes to make its return trip back to the opposite direction. Since Tokyo Station is the terminal station for Tokaido Shinkansen heading to Osaka and Hokkaido/Tohoku Shinkansen heading north, this quick turnaround happens many times a day.
You need to pay attention to the cleaning attendants who are in uniform carrying large bags. They are going to put up an incredible show that takes 10 minutes or less. Their bags have all sorts of secret (cleaning) weapons packed away, such as a dustpan, a folded broom, cleaning cloth and trash bags.
The cleaning crews have to wait until all passengers are out of the train cars. They are waiting for you at the door to receive your trash. Some passengers are taking their time getting off, and the attendants wait patiently but are eager to start their cleaning duty.
When they get to go into the car, the show gets very exciting. First, all the trash left in the compartment is collected. Then they wipe off each folding table, dust off each seat with small brooms, and sweep the floor. Then they turn all the seats around to face the opposite direction. They do this very quickly like a wave of seats folding and turning. At the end, a team leader comes in and check each row to make sure everything is in order and spotless. Each car has 20 rows of 5 seats. That makes 100 seats to clean in one round.
When a team of cleaning crew (4 to 5 in each team) is finished, they line up in front of the car and bow in unison as if the show is over. I was watching the clock, and they were all done in less than 10 minutes after they started the actual cleaning.
I think they take pride in what they do, and it shows. The Shinkansen car is always spotless for your enjoyable trips.
Next time I am on Shinkansen trains, I am going to bring all my trashes out when leaving the train, and make sure to keep my seat area tidy to help out these incredibly hard working crews. Oh, and vacating the seat and promptly exiting the train will help the crew start their actual cleaning quickly also.
NOTE: My observation was done on Hokkaido Shinkansen at Tokyo station which has fewer number of trains arriving and departing each day. I heard that Tokaido Shinkansen which runs many scheduled trains throughout the day has 12 minutes at Tokyo station, and 7 minutes is allotted to the cleaning as documented in this Youtube clip.