A coroner reminded motorists to continue safe and considerate driving which they have learnt in driving school when he was giving his findings on Wednesday at an inquiry into the deaths of three men in a road traffic accident earlier this year.

"Otherwise it will end up with devastating circumstances,'' said State Coroner Imran Abdul Hamid after a joint one-day inquiry last month into the horrific fatal crash along Yio Chu Kang Road on March 2 this year.

The inquiry heard that student Rammohan Subash Nair, 24, was taking his three friends home after a drinking session when he lost control of his father's car at around 3am that day.

He was driving at an estimated 100 to 120kmh while negotiating a left bend on a slope when the car veered to the left, flipped in mid-air and hit a pedestrian crossing signboard, a concrete structure, a lamp post and a tree.

Two of the rear seat passengers, technician Shankar Tharumalingam, 22, and student Harendran Banjatjaram, 23, who were not wearing seat belts, were ejected from the car through the rear broken windscreen.

Mr Shankar was pronounced dead at the scene at 3.15am while Mr Harendran died in hospital about two hours later.

The front-seat passenger, Mr Jamal Haneef Kader Sultan, 23, a logistics officer, survived and testified last month.

Mr Rammohan, whose blood-alcohol level was 92mg/100ml blood, 12mg above the legal limit, was unconscious. He was taken to hospital and died at about 1am the next day.

In his findings, Coroner Imran said the evidence was clear that the under-inflated tyres caused by nails embedded in the left front and right rear tyres was not the one and sole reason for the accident.

Driving at an excessive speed while negotiating a bend on a down slope could not be considered safe, he said.