I lived in China for over 10 years and saw the transformation of cities through the building high-speed rail connections. The first weekend of my time in China in 2005, I took a K-Train to Suzhou(about 100kms from Shanghai) to see the gardens, and it took about 55-60 minutes on the train and we passed through a couple of other cities along which I think were Anting and Kunshan.
Move forward to 2008 when High-Speed Rail started D-Train (“Dongche”, 动车) in China at 250km/h (155mph) and then later in 2010 the new G-Train (“Ggaotie”高é“) that can reach 400km/h (280mph) when the same trip between Shanghai and Suzhou now takes 23-32 minutes cutting the time in half.  HSR has been so transformative that some air routes in China no longer exist.
The high-speed rail(HSR) has transformed China and has been used to create new cities and relieve the transport stresses placed on major cities by decentralising the population of cities. Whilst we still continue the same work paradigm of working in offices in Central Activity/Business Districts we will require people to travel into “downtown” in the morning and then leave and return to their homes in the cities. Whilst we all still ponder the possibility of autonomous vehicle travel we have to look toward solutions including decentralising populations from major cities. Melbourne and Sydney have both now sprawled over large areas with populations of over 4 million, the density is low although increasing over the last decade there is still major stress on the transport system.
The has been an ongoing discussion for the last 30 years of a high-speed rail line between Melbourne and Sydney due to the number of flights between the cities (one of the busiest in the world) and also due to the fact that they are the largest populations in Australia. However, this discussion often doesn’t go beyond expensive feasibility studies. I think that the premise of connecting the two biggest cities is the wrong discussion around high-speed rail infrastructure but in fact, the discussion should be focusing more on connecting regional cities (Geelong, Ballarat, Bendigo and Newcastle, Wollongong and the capital Canberra) to the main centres to decentralise the populations and increase business centres.
Through HSR we could see populations move and grow these regional centres with most populations being 70,000 to 400,000 people whilst the major cities have grown beyond 4 million.
For Melbourne, it would seem the best solution would be to first connect Geelong and Melbourne via Avalon Airport with a travel time of 18-24 minutes cutting the current travel time(1 hour) by over 60% and would connect Melbourne’s second airport to the city.
In Sydney, it would seem that connecting Canberra via the new airport at Baggerys Creek and Wooloongong would be the first route due to the amount of travel (car and air) that happens between the cities. Currently, the travel time is 4 hours 8 Minutes to travel 280-350km, which high-speed rail this could be cut to 1hr 30 – 1hr 45 based on two intermediate stops.
The financial benefits for regional cities are generated through increased population growth and tourism and reduced costs for major cities due to the reduction in the needs creating new housing and infrastructure.
Australian Governments have attempted to shift populations by moving departments or statutory authorities to regional cities, however, it is often hard to get people to relocate due to the distance from friends and family.
The issue with most planning studies and models we see from planners and architects show increased density in the central business district with higher towers. This is not the answer but will increase the current problems due to increase density and reduction in open space.
There are numerous issues around the current population growth in Melbourne and Sydney, each having grown by over 1 million people in the last decade, however, we constantly keep looking at the solution of increased density with new surburban rail stations on overcrowded lines as the silver bullet. However, there are numerous regional cities that have populations of less than 10% of major cities and by connecting these to the major business districts through rail and increasing the density of office buildings and mixed use in these centres rather than increasing residential populations through large towers.
These idea is only one of many but it is a large idea that could make the largest difference to Australia’s major cities.