alternative routes exist even now, the primary issue is of MPS.
unfortunately, even the new lines being built aren't being build with an eye on the future and most of them are at most 110 fit; many are usually cleared for 80 or 100
As sanjeev sir said below, even if the main alternative route is made 130 fit it will go a long way in alleviating the problems of the people, beside giving the people on the alternative line faster options to travel, but no steps are being taken in that regard.