The A5 between Abbey Hill Roundabout and Old Stratford Roundabout has reopened at 14:20pm.
The A5 closed at 5am this morning after a serious collision took place.
The section of the busy dual carriageway remained closed whilst an investigation took place.
National Highways has reported that a vehicle and a pedestrian were involved.
Thames Valley Police says: "Thank you to the public for their patience whilst the closure was in place."