How come there are sometimes multiple buses at the Noorderlaan stop?

During peak hours, four buses operate. To ensure service every 15 minutes, they wait at the Noorderlaan stop. Each bus waits until the next quarter hour to depart (x:00, x:15, x:30, x:45) and then runs the entire route. The Noorderlaan stop is most suitable because there is enough room for some Bike Buses to wait. With this system, we aim to serve all stops every 15 minutes. That way, we ensure that buses maintain their frequency and do not overtake each other.