Devil of a job, but somebody has to do it

I have always wondered why the more hospitable environment and terrain used by much of the rail line between Gisborne and Napier isn’t considered as an alternative route in places where it is a viable option.
Obviously the parts that are vulnerable to repeated damage on both rail and road links (Beach Loop dropout and Devil's Elbow) could be excluded from this proposal, but there must be a case for making use of the more reliable parts of the infrastructure. This could include rail bridges currently in place but no longer used because the whole rail link is closed - eg, the existing rail bridge that currently straddles the Waikare gorge at Putorino, if used for road traffic as well, could save the cost of building an adjacent bridge just up the road.
Just a thought