A feasibility study into high speed rail (HSR) by the federal government released earlier this year got a few people talking about the possibility of HSR in Australia. However, the high cost ($70 billion to $110 billion just to build the infrastructure) seems very excessive to me, especially considering all the benefits you could get from investing that money into the suburban rail networks.
What did catch my eye was a piece on medium speed rail on Transport Textbook, which suggested connecting Sydney and/or Melbourne to some of their satellite cities (Newcastle, Wollongong, Bendigo and Ballarat). Rather than aiming for the 250km/hr to 350km/hr required for HSR over long distances, increasing speeds to something around half of that over a much shorter distance and still obtain a significant benefit, but at a much lower cost. For example, increasing the average speed to 112km/hr would allow a Newcastle-Sydney trip to take just 90 minutes (compared to the current 170 minutes).
A very interesting take on the question of is fast enough good enough?