I spent quite a bit of time construction a long circular railroad, only to see that it isn’t giving a frequency in the route planner. Presumably because of this, no passengers are using it, even if the time between two stations is a few minutes.
Is this working as intended? Did I go over the maximum distance, or time?
Frequency is not the time trains take to travel between stations but the time between one train arriving at a station and the next train at the same station. Thus if you have a very big loop with only one train on it the frequency will be very poor and no-one will use it. You will need to add more trains to make the frequency better.