Waiter, Joel Magalhaes from Capitan Torres Spanish Restaurant, which is adjacent to where the incident occurred, said it was “very, very shocking”.
“The truck stopped a few metres from the body,” Mr Magalhaes said.
“It was very, very strange atmosphere, people weren’t screaming but were very alert and worried – everybody was calling the ambulance.”
The truck driver in his 40s has been taken in for mandatory blood and urine testing.
Moments after the incident happened, witnesses said a shop keeper covered the rider’s body with a white sheet.
Westbound lanes have now reopened on Liverpool Street and also on George Street in both directions.
The Westbound diversion off Liverpool Street in to Pitt Street and Kent Street have also been lifted.
All emergency service crews have left the scene. Motorists are advised to continue to exercise caution and allow extra travel time in the CBD.