A collision closed a section of the M4’s westbound carriageway for more than five hours on Sunday morning.
A black Renault Clio and a silver Land Rover Discovery collided near Leigh Delamere Services, in Chippenham, at 2.20am.
The Land Rover hit the central reservation and rebounded into the hard shoulder.
The Clio struck the hard shoulder barrier before catching fire.
The Land Rover’s driver, who was not injured in the crash, got out of his vehicle and rescued an unconscious man from the back of the Renault Clio, before it became engulfed in flames.
Police officers, paramedic teams and firefighters attended the incident and Clio’s three passengers were taken to Southmead Hospital, in Bristol, by ambulance.
It is believed that the three suffered serious injuries.
A fire crew put out the burning car and the Highways Agency closed the westbound section of the M4 between junction 17 and 18 from 2.45am until 8am to allow Wiltshire Police’s specialist collision team to investigate the scene.
A police spokesman said: “We are urgently appealing for any witnesses who have information about this collision.”
Anyone with information about the incident can inform the police by calling 101 and asking for the roads policing team, or alternatively they can call Crimestoppers on 0800 555 111 where information can be left anonymously if preferred.