Two accidents happened at the same spot in quick succession along the Pan Island Expressway (PIE) on Tuesday night (May 31).
One of them involved a motorcycle and a car while the other was a seven-vehicle pile-up.
The police said they arrested a 38-year-old-man, who crashed his car into a motorcyclist for suspected drink driving.
Meanwhile, two people — a 50-year-old driver and his 54-year-old passenger — involved in the pile-up were taken to Changi General Hospital, the Singapore Civil Defence Force (SCDF) told AsiaOne.
Three others were assessed for minor injuries but refused to be taken to hospital, SCDF added.
Video clips circulating on social media showed seven cars involved in a chain collision, with one Toyota mounting another.
Police investigations are ongoing.