1A (railway/bus) timetable or operating schedule; a common abbreviation of 運行ダイヤ, frequently heard in announcements about delays or service disruptions.
今朝は電車のダイヤが乱れていて遅刻した。
This morning the train timetable was disrupted and I was late.
通勤のダイヤを確認してから家を出た。
I checked the commute timetable before leaving home.
ダイヤ改正でこの路線の本数が増える。
A timetable revision will increase the number of services on this line.
2A railway-industry technical term for the graphical chart (diagram) that plots train movements against time and position — the origin of the more common 'timetable' sense above. Rarely heard in everyday conversation; mainly used by dispatchers and operations staff.
運行管理者は列車の位置を示すダイヤを見ながら遅延に対応する。
Operations staff respond to delays while watching the diagram that shows train positions.