> a 20 minute drive usually takes about 20 to 30 minutes due to the detours
That variability makes the whole system much less interesting once a change is involved, e.g. if the on-demand shuttle is only supposed to operate across the local area, but not for longer journeys traversing the whole city, especially if the connecting fixed-route transport runs less than every few minutes…
Or even without changes, but when you have some other external schedule constraints, because in those cases you always have to budget for the longer journey time, negating the benefit of direct routing somewhat.
That variability makes the whole system much less interesting once a change is involved, e.g. if the on-demand shuttle is only supposed to operate across the local area, but not for longer journeys traversing the whole city, especially if the connecting fixed-route transport runs less than every few minutes…
Or even without changes, but when you have some other external schedule constraints, because in those cases you always have to budget for the longer journey time, negating the benefit of direct routing somewhat.