A man is in hospital with life-threatening injuries after he was hit by a vehicle on the M3 at Winchester.
Police were called to the northbound slip road at Junction 11 following the incident at 4.06pm on Sunday.
Hampshire Police said a man was seriously assaulted on the carriageway and had fled the scene to evade further injury.
A 59-year-old man from Southampton was taken to Southampton General Hospital with serious but not life-threatening injuries and has since been discharged after treatment.
The suspect, a 21-year-old man from Winchester, was seen on the hatched markings and was subsequently involved in a collision with a vehicle.
He was taken to Southampton General Hospital with potentially life-threatening injuries.
The M3 motorway was closed for several hours to allow officers to investigate the circumstances of the incident and was subsequently re-opened at around 11.30pm.
Officers are keen to speak with anyone who may have information which will help aid the investigation as they begin to establish the exact circumstances of the incident.
They're asking anyone who witnessed the assault or has dash-cam footage to get in touch.