It weighed over 2000 tonnes and was about 470m long, she said.
The crossing was protected by stop signs but did not have barriers or flashing lights.
By a stroke of luck two intensive care paramedics were in the rural area in the Buller Gorge.
"So she received some quite advanced care in this paddock before the helicopter arrived.''
One accompanied her in the helicopter to Christchurch.
Mr Blankenstein said one intensive care paramedic had been in nearby Reefton doing some training. The other, the district operations manager, was in the area because the St John chief executive was visiting.
An emergency medical technician crew and two rural nurse specialists from Reefton also attended.
"So we had a vast number of responders. So this lady got absolutely the best care that we can possibly provide in a national context and in a very short space of time as well.''
St John wouldn't have been able to administer some of the skills it did today without all those staff present.
It was not yet known whether the woman was a local.
