The mystery passenger who might have witnessed an incident between a cabby and a motorist which left the latter unconscious for over a week has come forward.

The incident took place on April 9, and yesterday, police said that a woman in her 30s had offered to be a witness.

Her account of what happened could help police piece together the events that have left financial adviser Alex Lim, 30, with severe head injuries and a taxi driver suspended from duty.

Family and friends had appealed to the woman through The Straits Times to offer information on what she saw that evening.

It all began with a collision along Paterson Road between the Comfort taxi and Mr Lim's Mazda. The drivers then pulled up along Scotts Road, got out and exchanged words.

Mr Lim's girlfriend Yvonne Lin, who was in the car, said the cabby returned to his vehicle before the dispute was resolved and tried to drive off. But Mr Lim stood in front of the taxi.

She added that as the taxi began moving, Mr Lim fell forward onto its bonnet.

He fell off when the taxi stopped, landing on the back of his head. This was when the female passenger in the taxi alighted, she said.

The cabby, a relief driver in his 60s, was arrested and is being investigated for a rash act causing grievous hurt. He is out on bail.

Mr Lim, who has had two operations, will be operated on again today to open a hole in his throat so phlegm can be removed, said Ms Lin.

Doctors have reduced his anaesthesia levels, leaving his family to look out for signs of his coming around. There have been none so far, added Ms Lin.

Police, who have dealt with 242 road bully cases in the last three years, offer the following tips to those who encounter bullies on the road:

Remain calm. Do not further agitate the bully with gestures or words.

Note the bully's vehicle number and file a police report.

If confronted by the bully, call the police. Stay in your locked vehicle and await help.