The issue of service levels and safety at crossings, especially during peak hours, is critical, and overpasses can significantly increase the cost of the project. It is also true that the route coverage is limited: if it does not pass through key population and employment centers, its effectiveness is questionable.
On the other hand, it is worth acknowledging that converting an old railway into a transport corridor is an idea that could be viable if properly developed. Perhaps not in the form of light rail transport, but, for example, as part of a hybrid solution with BRT or with phased implementation.
Something similar has been described on Tuttotek.
