Clock-face scheduling

A clock-face schedule, also cyclic schedule, is a timetable system under which public transport services run at consistent intervals, as opposed to a timetable that is purely driven by demand and has irregular headways. The name derives from the fact that departures take place at the same time or times during the day. For example, services with a half-hourly frequency might leave at 5:15, 5:45, 6:15, 6:45, 7:15, 7:45 etc.

The goal is to enhance the attractiveness and versatility of public transport. Clock-face schedules are easy for passengers to memorise because departure and arrival times occur at consistent intervals, repeating during the day. A regular repeating schedule over the whole day can also improve services during off-peak hours. Clock-face timetables can be attractive for transport operators because the repeating pattern can allow the more efficient use of personnel, infrastructure and vehicles, and also make resource-planning easier.

Repeating timetables were first developed at the end of the 19th century, for local public transport, such as trams, rapid transit, and trains in the vicinity of large cities like New York City. A clock-face schedule is used currently for railways in many countries such as the United Kingdom, Switzerland and Germany. It is also used for urban transport systems like the New York City Subway system and London Underground.