Having worked on railways around the world, your categories of 'modernisation' are rather wide-ranging and have slightly-different impacts. However, assuming more widely that you mean a step-change in quality through the provision of faster, more frequent services using newer (probably electrified) trains, then you should be aware of the 'sparks effect'. In addition to the passenger traffic gains that might be forecast through the usual application of elasticities to the change in generalised costs, many countries (since original observations in Britain in the 1960s) have found that the increased marketing and promotion associated with a major rail upgrade can lead to even larger increases in traffic.

However, that doesn't necessarily mean that these railways will be profitable (or even commercially-successful), because of the underlying economic problems with railways: e.g. high capital costs to be paid off by users for whom subsidised road transport is often very competitive. (NB: 'Subsidised' = when externalities, such as the impacts of accidents are taken into account).

It's currently a work in progress. The Government is trying to revamp the railway system all over the Country.