He then flies through the air before landing motionless in the road several vehicle lengths away.
A witness can be seen holding their hand to their mouth in shock at the point of impact, at 3.40pm on Thursday, January 14.
As the victim lies sprawled motionless in the middle of the road, around 10 passers-by are seen standing around in disbelief.
One man, who does not want to be named, was working in an office at nearby car repairs specialists 1st Class Garage when the incident happened.
He said: "I ran outside to see what happened and the gentleman was just lying there in the road.
"It's a horrible thing to witness. People who were gathered around him said the car came screaming around the corner and didn't stop.
"It was awful, and I initially thought it was two cars that had collided because it was that loud.
"The victim was conscious but he was bleeding from his head. I just saw him leaning against the van parked on the side of the road.
"There was someone covering him up with a coat trying to help him but there was nothing else we could do until emergency services arrived."
Officers now want to trace the drivers of a taxi, a silver van, a Ford Focus and a black parked car in the hope they might have crucial information.
Sergeant Dan Pitcher said: "We are very keen to trace the drivers of the taxi, the silver van, the dark Ford Focus and the black parked car.
"We think you could give us vital information we need to identify the driver.
"The Fiat drove off leaving the victim for dead and clearly they would have known they had hit someone.
"The pedestrian, a man from Hove, suffered serious head injuries and is thankfully making a recovery."
Anyone with information is asked to phone Sussex Police on 101, quoting Operation Northdown.
