A former cabby and a car driver involved in an accident two years ago have been sued for negligence by one of the four taxi passengers.

The action has been initiated by National University of Singapore (NUS) student Ting Jun Heng, the passenger in the centre-rear seat in the taxi at the time of the accident.

He was sitting beside fellow undergraduate Kathy Ong Kai Ting, 19, who died in the accident.

Mr Ting, 23, who now walks with a slight limp and has a speech impediment, is seeking unspecified damages from former cabby Yap Kok Hua, 56, and Mr Ng Li Ning, 23, the driver of the Nissan that crashed into the taxi.

A four-day trial to determine liability opened in the High Court yesterday.

Damages will be assessed separately and will be borne by the defendants' insurers.

The two defendants claim that Mr Ting was not wearing a seat belt at the time and was partly liable for his own injuries.

Both defendants have also engaged experts to testify on the speed of Mr Ng's car.

Mr Yap's expert, Mr Neil Mackay, estimated that the speed was between 87kmh and 93kmh at the point of impact; while Mr Ng's expert, Mr John Ruller, estimated the speed to be between 74kmh and 82kmh just before impact.

The speed limit is 70kmh.

On April 19, 2018, Mr Ting, with Ms Ong, Mr Zon Lim Thou Jung and Mr Lim Jin Jie, boarded Mr Yap's taxi at Clementi Mall in Commonwealth Avenue West at about 7.30pm.

Their destination was Tembusu College at NUS.

The cabby was making a discretionary right turn at the junction of Commonwealth Avenue West and Clementi Road when Mr Ng's car, coming from the opposite direction, crashed into the taxi.

Ms Ong died from multiple injuries in hospital about three hours later. Mr Lim Jin Jie suffered bleeding in the brain and a spinal fracture, while Mr Zon Lim, who was seated in front, suffered a brain injury.

Both men, who were 22 that year, were hospitalised for eight days.

Mr Ting suffered traumatic brain injury and arrived at the hospital in a vegetative state.

In August last year, Mr Yap was jailed eight weeks after pleading guilty to causing Ms Ong's death and causing grievous hurt to the three other passengers by his negligent driving.

Mr Ng was charged with dangerous driving, and his case is pending.

In his civil suit, Mr Ting said he could not recall the events of the accident but believed he was wearing a seat belt at the time.

His lawyer, Mr Ramasamy K. Chettiar, said a passenger need not prove liability against either driver.

Mr Yap's lawyer, Mr Teo Weng Kie, argued that Mr Ng drove in a "particularly egregious manner".

The lawyer said video evidence showed Mr Ng's car was going at high speed and narrowly missed another vehicle just before colliding into Mr Yap's taxi, which then spun a few times.

Mr Teo said the cabby could not have taken any evasive action, given Mr Ng's speed.

Mr Ng's lawyer, Mr Anthony Wee, argued that his client had the right of way and the taxi suddenly encroached into Mr Ng's path.