He was warned for speeding just four months after getting his driving licence on March 31 last year.
Yet, just one month later, full-time national serviceman Herman Shi Ximu, now 19, drove his Nissan GT-R at speeds of more than 100kmh at a carpark near the Singapore Indoor Stadium.
He hit a car which had the right of way, injuring the driver.
Yesterday, Shi was sentenced to six weeks' jail and disqualified from driving for 11/2 years.
He had pleaded guilty on Oct 4 to causing grievous hurt to another motorist by performing a rash act.
In handing down the sentence, District Judge May Mesenas said: "(Shi) was given a warning... but threw caution to the wind."
Shi committed the offence at a surface carpark along Stadium Walk on Aug 27 last year.
He had gone to a nearby motoring event earlier that day. At around 5.45pm, he stopped his Nissan GT-R, which was registered in his name, at one end of the carpark before rapidly accelerating.
He then drove through a non-signalised junction at a high speed.
Deputy Public Prosecutor Soh Weiqi said: "At the second non-signalised junction within the carpark, the accused failed to stop at the stop line and he did not give way to the victim, who was travelling from his left, to the right."
She said contractor Teong Hien Sing, 66, was driving his Toyota Corolla and had the right of way when Shi's car hit his vehicle.
According to a report from a Health Sciences Authority forensic scientist, the teenager covered a distance of at least 72.2m at a speed of between 104kmh and 121kmh at that time.
Later that same day, Mr Teong went to Changi General Hospital as he felt pain in his chest and neck. X-rays revealed that he had two fractured ribs.
He was given two weeks of medical leave.
Mr Teong later went to Mount Elizabeth Medical Centre and an MRI scan of his spine on Sept 9 last year, showed degenerative changes.
He had an MRI brain scan about a month later and doctors found that he had a subdural haematoma - a collection of blood between the covering of the brain and the brain surface.
Mr Teong was admitted to Mount Elizabeth Hospital and had surgery to remove the haematoma. He was discharged on Oct 25, and given 32 days of medical leave.
Shi is now out on bail of $10,000 and is due to surrender himself at the State Courts on Dec 1 to begin his sentence.