Release Train? Or Release Metro? What cadence works for you?

We have all heard about the Release Train as a concept for managing agile at scale. It's a pretty good metaphor. A train leaves the station according to a set timetable. The passengers fill up the train when they are ready to depart and if you arrive late, you miss the train and catch the next one. Software releases under a release train work the same way - the train leaves the station (releases to production) according to a set timetable. While waiting, the train gets filled with completed features and if a feature arrives late, it waits for the next train.

Not a bad metaphor, and, for some businesses, not a bad way to organise a release cadence either. However, for other businesses, a release cadence like that is not appropriate. It may be too fast. Or too slow. Maybe what you need isn't a train, but a metro. On a metro, smaller trains arrive and leave so frequently that no timetables are needed. Just turn up and hop on the next train. Or is your release more like an ocean liner? Their arrival and departure is large, infrequent and marked by a lot of fanfare (and more than a little cursing by those doing the hard work of steering the thing in).