how would they know that it will be popular before it even
starts?
They will have to make it popular. DD fleet, good frequency,
express route to CBD. Over time people will switch to the route if
they find that it doesn't take too much more time than MRT (10-15
mins is okay) and the experience is good.
If I live in Tampines and have to stand all the way to CBD, I
would not take a bus. I will stop using the service. If the
experience for me is bad, I will not switch to bus - so very
important to deploy DDs from day 1 to make sure people have a good
experience and are willing to shift.
Marketing experience talking ;)