Andrew Dean, 46, from Wesham, was found in the carriageway at the junction of Freckleton Street and the A583 Kirkham Bypass with head injuries yesterday. He was pronounced dead at the scene.
Police were called to the scene at 4.15pm to reports of an incident.
Detectives believe Mr Dean had been driving a white Renault Master van westbound on the A583 when he was involved in an altercation with another motorist driving a metallic blue Nissan Micra car.
Both vehicles stopped close to the junction with Freckleton Street and Mr Dean got out of the van to speak to the Nissan driver. It is believed the Nissan then crashed into Mr Dean, causing fatal injuries.
An 18-year-old man and 18-year-old woman both from Ashton-under-Lyne, a 17-year-girl from Stalybridge, and a 16-year-old girl from Audenshaw were arrested on suspicion of murder.
The teenagers were stopped in their car at a road block between junctions 6 and 5 on the M61 at 4.45pm.
Police are looking to trace anyone with dashboard mounted camera footage of the incident, as well as any footage of either vehicle before the collision took place.
It is believed the Nissan Micra travelled through Penwortham, into Preston and towards Kirkham before the crash.
Det Ch Insp Eric Halford, of West CID, said: “These are tragic circumstances and my thoughts remain with Mr Dean, his family and friends at this sad time.
“While we have made a number of arrests we are continuing to piece together the exact circumstances of what took place.
“We have spoken to a number of witnesses at the scene and would like to thank those people, as well as the wider community in Kirkham, for helping to support our investigation.
“We continue to ask anyone who saw what happened but have yet to come forward, to contact us.
“We are particularly keen to speak to anyone with dashboard mounted camera footage of the collision, or anyone with footage which shows either vehicle travelling on the A583 in the moments before the incident.
“Furthermore we believe the Nissan, described as metallic blue in colour, was driven through the Penwortham and Preston areas towards Kirkham before the collision. If you saw this vehicle and have any information or footage, please contact us.”
Mr Dean's daughter Aimee Dean paid tribute to the 'amazing, thoughtful, caring and loving dad, granddad and husband' online.
Anyone with information should call police on 101 quoting log number 1068 of July 18, or independent charity Crimestoppers on 0800 555 111.