On which lines are time-based tickets valid?

The time-based ticket is valid on all BKK services (metro network, tram lines, trolleybuses, buses) as well as on regional buses: specifically, on lines 1–99,101–299, 900–999 and on suburban railway lines H5–H9 within Budapest’s administrative boundaries. You can use it for an unlimited number of transfers with trip interruptions, by validating it each time you board making sure that your last transfer falls within the time limit.