What started out as a joyful Chinese New Year outing ended in tragedy when a sleepy motorist momentarily closed his eyes, resulting in a crash that killed his mother.

His father and niece were also injured in the accident.

Peh Boon Wee, 48, was fined $10,000 yesterday and disqualified from driving all classes of vehicles for five years after pleading guilty to causing the death of Madam Jenny Goh Siew Hoong, 70, by negligent driving.

He also admitted to causing hurt to Mr Peh An Leng, 74, and his 13-year-old niece by driving in a negligent manner.

The girl cannot be named as she is a minor. All four are Malaysians.

The court heard that Peh had been driving from Malaysia in a car since 5am on Feb 16 after six hours of sleep.

Deputy Public Prosecutor Deborah Lee said Peh stopped once for breakfast at 9.30am and resumed driving about 45 minutes later.

After that, he stopped about three more times for toilet breaks, said the DPP, who added that Madam Goh and the girl, who were seated at the back, were not wearing their seat belts.

Peh was driving on the rightmost lane of the four-lane Ayer Rajah Expressway towards the Marina Coastal Expressway at around 1pm when he closed his eyes "for a while" as he was feeling sleepy.

Video footage showed that his Malaysia-registered car veered to the left across the second and third lanes before colliding hard into the rear of an SBS bus which was travelling on the innermost lane.

Peh's family members were taken to the National University Hospital where his mother died of extensive spinal injuries.

DPP Lee told District Judge Kan Shuk Weng that Mr Peh An Leng suffered abdominal injuries and the girl had injuries that included facial wounds and a bruised left knee. Court documents did not state if Peh suffered any injuries.

Peh, who was unrepresented, pleaded for leniency yesterday.

For causing death by negligent driving, he could have been jailed for up to two years and fined.

And for causing injuries by negligent driving, he could have been jailed for up to six months and fined up to $2,500.