Daiya (service schedule)

The operating plan that sets out when buses run and how many of them. The timetable at a bus stop is that plan laid out as a list, and it is normal for separate schedules to be drawn up for weekdays, Saturdays and holidays.

What daiya means

Daiya is the operating plan that sets out when buses run and how many of them. The word is a clipping of "diagram," the chart that plots train services against time, and buses use it in just the same way. The timetable posted at a stop is that plan laid out for riders. ダイヤ改正 (daiya kaisei) means a revision of the operating plan itself. A revision changes frequencies and times, so when you spot a notice about one at a stop or in a service announcement, checking the times of the trips you normally take is a habit worth forming.

The schedule switches with the day of the week

The most important point for riders is that there is not just one schedule. On most routes a weekday schedule, for the days heavy with commuters and students, is drawn up separately from a holiday schedule for Sundays and public holidays, and some routes keep a schedule for Saturdays alone. Even on the same route, a different day of the week means a different number of buses and different times. On some routes the mix of destinations shifts with the day as well, so what differs is not only the times but how many trips go where.

Without knowing how this works, you get the bewildered moment of "buses always come every 10 minutes on weekdays, but I went on Sunday and waited 20." Knowing it, you fall into the habit of checking which schedule today follows before you set out, and you can plan with room to spare even for travel early in the morning or late at night on a day off. Public holidays generally run on the holiday schedule even when they fall on a weekday, so they deserve particular attention. Some operators also draw up special schedules for the New Year period and the Obon season, so a glance at posted notices and announcements makes trips at the turn of a season a safe bet.

Reading it together with the timetable

Timetables at stops and on arrival pages normally have the weekday, Saturday and holiday columns printed separately. Simply confirming at the outset that the column you are reading matches today's day of the week heads off almost every misreading of the times. And once the word daiya is familiar, an announcement or notice saying 休日ダイヤで運行します, that buses are running on the holiday schedule, comes across without a moment's confusion. How to tell the columns apart and how public holidays are handled are explained step by step in our article on how to read a bus timetable.