What affects the duration of a planned journey?
a) Length of the journey.
b) Maximum speed in few lone sections of the journey.
It uses checkboxes, so you can check both.
They expect you to check only a), but b) is in my view also logically correct answer as if at any section even if it's shorter than 1 metres, if your max speed nears 0, duration of your journey will reach infinity. But it is worded in such a way that most people will get the hint that B) should not be checked.