Around 55 years, when the southern strategy was enacted to solidify racist support for Republicans.
Before that the parties were more mixed and it was the confederates and robber barons doing the damage. Before that it was the slave owners. And before that it was the colonizers. Before that it was probably whichever tribe had the best growing season or pointiest flint arrowheads.
I’m starting to second guess what the point of progress really is. Are we trying to ride humanity out until the heat death of the universe? Or just the next billion years before the sun boils our oceans away? Another 2000 years so today’s assholes can become deities? 52 more years the the US Tricentennial?
If you go by length instead of ridership it seems extremely plausible. Australia is a big place and building 2 lanes for mostly freight trains is an unnecessary expense.
Sidings/loops/passing tracks, allow trains to pass on a single track, and since things can be more regular scheduled (ideally anyway) with trains, they can work well enough and with much less track building needed.