The incident happened at around 1 am yesterday morning (Sunday 10th September) after a blue BMW was pulled over by a Hampshire Constabulary police car onto the hard shoulder of the M3 Southbound.
Police say that the driver of the BMW got out of the car and was struck by at least one vehicle.
A ambulance was called but the man died en route to hospital.
Hampshire Constabulary has referred the incident to the Independent Police Complaints Commission.
The Serious Collision Investigation Unit are currently investigating and appealing for witnesses.