Sydney-Melbourne HSR

The flight between Australia's two largest cities - Sydney and Melbourne - is one of the top ten busiest passenger air routes in the world, with just under 10 million passengers flying between the two cities in 2019. Unlike all of the other top ten flight routes, Sydney and Melbourne are not separated by water, and the distance between them is relatively short at 705 kilometres (438 miles). This is especially short compared to the vast landmass of Australia. Given the currently unavoidable impact of air travel on greenhouse gas emissions, rail services can provide an important alternative to transport large groups of people at speed over hundreds of kilometres overland, with fewer long-term environmental impacts. However, overland travel options between Sydney and Melbourne are currently limited. The state-operated NSW TrainLink runs a twice-daily "XPT" (Express Passenger Train) service, but the travel time is approximately 11 hours, which is slower than the 9 hours it takes to travel between the cities by car. These services only carry a small number of carriages with sleeper beds, and there are concerns for safety when travelling at high speeds on the aging track infrastructure, demonstrated most recently by a derailment at Wallan, Victoria in February 2020 which killed two people. One novel challenge for a high-speed rail connection between Sydney and Melbourne is the Australian Alps, a rare mountainous area in an otherwise largely flat continent that lies between the cities. The current railway network noticeably detours to the north of this mountain range, passing through the towns of Yass, Cootamundra, and Wagga Wagga before continuing south to the Victorian border at Albury-Wodonga. The current railway track also includes steep turns through hilly areas that would be unsafe to navigate at high speeds. A possible solution to these issues would be to create a new high-speed line that, starting from Sydney, follows the existing track, albeit with some modifications to remove steep turns, south-west to Canberra. This would be the beginning of a shortcut that bypasses the Yass/Cootamundra/Wagga detour on the current Sydney-Melbourne corridor, and incorporates Canberra, the national capital and eighth-most populous city in the country, into the network. Canberra station is currently at the end of the line from Sydney, and there are no direct rail services to Melbourne. Thus the shortcut could continue from Canberra with an underground tunnel travelling west for approximately 43 kilometres (27 miles), passing under the tallest of the Snowy Mountains and emerging near the town of Tumut in New South Wales. This would be shorter than several existing railway tunnels, including the functionally similar Gotthard Base Tunnel in the Swiss Alps at 57 kilometres (35 miles), underwater tunnels in Japan and the English Channel, and some metro line tunnels in China and South Korea. Construction would be aided by the fact that Canberra is currently building new rail infrastructure for its own light rail network, and Tumut is already a construction hub for the Snowy Mountains hydroelectricity scheme. A new railway line could then continue to travel south-west from Tumut, following along the existing Snowy Mountain and Hume Highways, to connect with the existing track at Albury-Wodonga and continue to Melbourne along the relatively direct existing track.