Work has started on construction of four machines - set to weigh more than 900 tonnes each - which will plough through an average of 120 metres of sandstone per week as they deliver the longest rail tunnels ever to be built in Australia.

In a joint statement with Transport Minister Gladys Berejiklian, state Premier Barry O’Farrell says the custom-made tunnel boring machines (TBMs) which will deliver two fifteen-kilometre twin tunnels as part of Sydney’s $8.3 billion North West Rail Link had been ordered and were now being prepared. “The North West Rail Link…