How often do trains run in Sri Lanka?

Service frequency varies a lot based on the route. Trains on commuter lines near Colombo can run all day. Some main intercity express services only run a few times, often about three or four departures per day.

Take the famous hill country line from Kandy to Ella. It does not have many trains each day. If you miss one of those specific express departures, you may end up waiting for hours. In some cases, you might have to push your trip to the next morning.