A pedestrian who was knocked down by an allegedly drunk driver in Sydney's CBD, before he lit a cigarette and strolled off into the night, has contacted police to say he is fine a day after the dramatic crash.

Police had held serious concerns for the health of the mystery man, who was shown in CCTV footage flying through the air when he was hit by the white Mercedes on Pitt Street about 12.30am on Monday.

The confronting footage shows the man tumbling down the street before coming to rest on his stomach, apparently unconscious. Witnesses rush to try to help him, as he lies motionless on the street.

Remarkably, the man is shown getting to his feet and walking to the side of the street, his head scraped and bleeding.