。
The train left on time.
Literal
Train [topic-は] on-scheduled-time [adverbial-に] left.
Uses 出た (plain past of 出る, 'go out, leave') as the main verb. 出る is colloquial and general; the more formal alternative 出発する is specifically about starting a journey. Both could work for a train leaving the station, with 出る lighter in register.