An accident occurred near 327 Jalan Besar yesterday morning, which left a car overturned in the middle of the road.
An eyewitness, Mr Mike Ho, said he was on his way to work at Sing Huat Hardware & Machinery, which is located in the area, when he saw the car flip over after colliding with another vehicle that was travelling alongside a double-decker bus.
Mr Ho, a sales manager in his 50s, immediately called for an ambulance.
His colleague opened the door of the overturned vehicle to assist the driver out of the car. The driver was wearing a sarong and looked to be in his 30s, Mr Ho said. He crawled out and walked to the side, looking stunned, Mr Ho added.
Another eyewitness, Mr Jay Lim, 48, told reporters he was awoken by the crash, despite being 15 storeys up at home.
Out of his window, Mr Lim saw the accident and the traffic congestion it caused.
He said: "All the cars had to filter to the right side of the road. The jam lasted around one hour."
When Mr Ho realised the congestion the accident had caused, he and his colleagues gathered LED-equipped safety vests and traffic light batons from their hardware store and helped direct traffic past the accident while waiting for the ambulance to arrive.
Mr Ho said: "We were afraid other people will get into an accident. We had the equipment to help so we wanted to make it easier for other cars while the authorities were coming."
The Singapore Civil Defence Force (SCDF) said they were alerted to the incident at 8am yesterday.
A spokesman said a person was assessed by SCDF paramedics but refused to be taken to hospital.