He was thrown almost 40m, landing in gravel at the side of the road and dying at the scene.
Trotter, who left Dannevirke High School at the end of 2012 with a scholarship and the boys' award for excellence in character and athletics, accepted responsibility from the outset, said lawyer Cam Robertson, and pleaded guilty "at the earliest opportunity" to a charge which carries maximum penalties of three months' jail and a $4500 fine.
Calavrias' family and friends travelled from as far as Tauranga and Wellington and were in court in numbers, wearing black arm bands embroidered "Nicolas Calavrias ONZM Our Man of Steel" as widow Mariana and son Nick Calavrias jnr read victim impact statements to the court and to Trotter, as he bowed his head in the dock, watched also by his own family.
Mrs Calavrias, married to her husband for 46 years since they met when she was 18, said: "I am completely broken. This unexpected tragedy has completely destroyed our small family."
"Life has lost its meaning for me, I have no sense of purpose," she said, highlighting that she now has difficulty sleeping, is medicated to help her, and she doesn't know how she will get on with life without her husband.
Her son said he not yet returned to work in his own business as he struggled to accept the loss of his father and the impact on the family, particularly his mother.
"Dad died without his dignity in one of the most violent of ways one can imagine, our lives are now consumed with negativity and hurt," he said.
It was a preventable tragedy, he said and the defendant should have seen his father multiple times in the 13 seconds it took from when he turned on to the straight to where the impact happened.
"Aspects of that day don't sit right with us," he said in a statement afterwards. "We are left feeling very uncertain. These areas of uncertainty are difficult for our family."
Judge Adeane said Trotter had a high-achieving and unblemished personal history, and the case was dominated by his remorse.
He said judges acknowledged such cases are the most difficult to sentence, where "the situation is out of all proportion to the fault incurred.