When Ferreira stopped abruptly, Allemann crashed into the back of the car and fell, breaking his left leg.
Judge Ryan said once the adrenaline wore off the pain was agonising for Allemann, making for two sleepless nights in hospital.
The fracture required a metal screw and Allemann would need further surgery, possibly a hip replacement later in life, the judge said.
Prescribed tramadol and morphine also had a big impact on Allemann.
The injury caused Allemann - a 46-year-old business analyst - to miss out on some of the "important" moments in his life - golfing, mountain biking and family holidays, Judge Ryan said.
Allemann's young son saw dad as "a superman" and could not understand why he could not get up and play, the judge said.
"All inall it has not been a happy time at all for Mr Allemann."
Ferreira's defence lawyer, Geoffrey Anderson, said road rage was a nationwide problem - "we think our cars are our castles".
It should be noted the collision happened at the rear of the car and Ferreira reported what happened at a police station, Anderson said.
The judge said the February 28 crash was not an accident and it was concerning Ferreira had tried to explain it away.
He was charged with driving dangerously causing injury and failing to stop to ascertain injury.
Failing to stop to check for injury is an "example of cowardice" that is so concerning Parliament had made it unlawful, Judge Ryan said.
Anderson said Ferreira had taken responsibility by entering guilty pleas, writing a letter of apology and presenting a bank cheque for the full sum of reparations. .
The former electrical engineer was on the pension and the sum had "drained him" of funds, forcing him to sell his vehicle, Anderson said.
Judge Ryan noted Ferreira had failed to help the cyclist, instead driving off towards Takapuna before a member of the public confronted him.
He also had been previously fined for a dangerous lane change, but had no prior convictions, she said.
The judge sentenced Ferreira to six months' community detention, six months' supervision and ordered him to attend programmes as directed by probation officers.
He was also disqualified from driving for 20 months and ordered to pay Allemann about $9580 in reparations.
Speaking after the case, Allemann said he felt Ferreira lacked remorse. He also said he was yet to see the apology letter.
"There needs to be more tolerance, more respect for everyone."
People underestimated the speed cyclists could reach and the consequences when things went wrong, he said.
"I mean he could have easily killed me," Allemann said.
"I'm constantly aware there is a chunk of metal in there [his leg] that was not in there previously."
Allemann had not been cycling to work since the incident because he was too fearful of going past the same driveway, but he felt reassured that Ferreira had been disqualified.
"It's been bad for him, bad for me. There's been nothing good out of it."
