"A woman was in the back of the van and I think she was knocked around quite a bit.
"It could have been much worse."
The front of the van was crumpled and the windscreen was shattered.
Three nurses who were passing by stopped to help until emergency services arrived while other motorists directed traffic, he said.
Two fire engines, two ambulances and about four police cars were at the scene.
Constable Rich Martin said the van had been heading to the women's prison in Auckland with a 49-year-old female remand prisoner and two Corrections officers on board.
The female prisoner was taken to Tauranga Hospital with possible spinal injuries and one of the Corrections officers was taken to hospital with whiplash, Mr Martin said.
The drivers of the van and the crane were uninjured.
Mr Martin said the crash caused delays for commuter traffic which was backed up in both directions.
Both lanes reopened at 4.45pm.