Firstly I'm not suggesting there is any "magic" to std gauge at all. Certainly there is no real engineering benefit and from a purely engineering perspective broad gauge is obviously superior, but with a greater burden.
I agree that there is plenty of heavy haul narrow gauge.
What I am talking about is a broader view of the transport task in SA and what part rail should play.
I'm also talking about interoperability, optimising operating costs, and a broader standardisation package.
At the end of the day the railway is merely a transport corridor - like a road.
At the moment, that metro "road" cannot be used by anyone other than a small proportion of rollingstock that has been built specifically for this network and only the carriage of passengers (who, by the way, pay very little of the cost of the provision of this service).
That same "road" has, what, one big "bus" over it once every 15 minutes? These "buses" are heavily loaded in peak hour but outside of that are relatively poorly patronised. ARTC on a good day have about 24 trains (on average one per hour).
DPTI also need own and maintain a bespoke fleet of maintenance equipment. They cant just roll in the AK cars off the interstate network for track geometry, they cant just ring ARTC, Transfields or Hollands to hire a Tamper, or Regulator, they have to keep their own capability.
Every time an ultrasonics run, grinding or other program needs to be run the equipment needs to be gauge converted and re certified. This comes at a cost both in time and money.
Every time they procure something it has to be "special". Special rollingstock, Special Sleepers, Special track gear, . This all costs the state a fortune.
Whilst the pure economics may not stack up in the immediate short term, my view is that conversion to std gauge would provide broader benefits and efficiencies to the state.
On the Seaford Line comments - it doesn't help when the same govt that invests mega dollars in track upgrade, electrification and new rollingstock, then goes and build a 1/2 billion dollar freeway alongside it. What did they think was going to happen?