alignment must necessarily pass through several National Parks and other regions of environmental significance, which could count against the selection of this corridor. Additionally, a station in central Canberra is difficult to achieve on this alignment; it would most likely have to be located at Canberra Airport or Queanbeyan. Canberra—Sydney Inland — The railway would exit Canberra to the north or east on a new alignment, roughly following the Hume Highway corridor through Goulburn, Bowral and Campbelltown. Entry to metropolitan Sydney could be effected by utilising the existing East Hills and Airport lines via Sydney Airport. Coastal — This corridor would be the same until Goulburn, where the line would turn east towards Wollongong. This alignment would present major engineering challenges due to having to cross the Illawarra escarpment twice, necessitating a tunnel on the southern approach, and several tunnels in the order of on the northern exit from Wollongong. The line could then utilise the undeveloped F6 Freeway corridor from Sutherland to Sydney Airport, from which it would use the subway system to reach Central station. Some have suggested an alignment to Nowra, thereafter continuing to Wollongong and Sydney, however the engineering and environmental considerations on such a route would be significant. Sydney—Brisbane Newcastle leg — Due to the density of existing development and the formidable terrain, there is no easy way of exiting Sydney to the north. One option is to use the North Shore line to reach Hornsby, whereupon a new alignment would follow the existing Pacific Motorway corridor, cross Broken Bay via bridge or tunnel and enter Woy Woy and Gosford via a series of tunnels and viaducts. A second option is to tunnel from North Sydney directly to Woy Woy via a tunnel (making it one of the longest tunnels in the world). The alignment would then continue to Newcastle following the existing road and rail corridors. This route could use the Sydney Harbour Bridge if two of the existing highway lanes were returned to rail use. Inland — From Newcastle, the line would transit the Hunter Valley through Singleton and Muswellbrook before crossing the Great Dividing Range at Ardglen. After Tamworth, the line would have to climb to over above sea level to reach the New England Tableland. After Armidale, it would climb even higher (peaking at above sea level) before reaching Glen Innes, Tenterfield, Warwick and Toowoomba. The existing rail corridor on the