Large part of Japan’s population relies on public transportation. Punctuality is an important part of Japanese culture, especially work culture. It’s not uncommon to arrive 10 minutes earlier. If you start your work at 8:00, you are expected to actually start working at 8:00, not arrive in the office at 8:00.
Train delay = office trouble?
Therefore punctuality of railways, metro and buses is a big thing as well. When a train arrives 2-3 minutes late, station attendants apologize to exiting passengers, and official apology is likely to be issued on official website of railway operator. When a Japanese train arrives 5 minutes late, things get serious. To avoid getting in trouble at school and workplace, passengers are issued chien shōmei sho, an official delay certificate.