Last month an Auckland District courtroom heard that Hartnoll had parked the car and applied the handbrake, but had not put it park.
While leaning over in the car, he hit the accelerator pedal, causing the car to lurch forward and through a barrier, plunging to the street below.
The car hit a parked Nissan below, narrowly missing two women who were inside it at the time.
A police witness told the court the car being left in drive was the primary cause of the crash.
Alcohol was not a factor.
The safety of the car park's barriers was contested in an earlier court case, but it was found the audited car park building was "generally" safe.
Judge Field acknowledged the physical and emotional toll Hartnoll had suffered in the aftermath of the crash and so did not consider a fine or community work to be appropriate.