Officers received a report of a collision involving a car and a pedestrian on the A1, near Haggerston Castle Holiday Park, at around 4.47pm.
Police and emergency services attended and the 76-year-old injured man was taken to the Royal Victoria Infirmary in Newcastle with life-threatening injuries. He is currently described as being in critical but stable condition.
The road was closed for approximately five hours while the vehicle was recovered.
Police are urging anyone who saw what happened in the minutes leading up to the collision to contact them.
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Anyone with information which could help the investigation is asked to contact police on 101 quoting reference 846 – 17/11/2018 or email the investigating officers at [email protected]