So can it be said, as long as a line’s frequency less that 20 minutes, people will use the line?
No, because waiting time is also being taken into acount.
Max travel time a passenger is willing to walk on his own is 20
travel time is calculated by: walktime from point A to station+wating time+drive distance+walktime to point B.
the more stations are between A and B the more waiting time. So lower the frequency is for us (the transportation service company, the only way to increase the travel distance of passengers (more people are willing to take the transportation service and then will help the city grow) and to lower the travel time of passengers, which has the same results.
the game is all about frequency.