The M23 has been closed this afternoon (Sunday) after a serious accident between Junction 11, A23 (Pease Pottage) and Junction 10, A2011 (Crawley).
There is a diversion in operation - traffic can divert through Crawley along the A23 Crawley Avenue, rejoining at Junction 10.
Both junctions 10 and 11 in both directions were been closed for the air ambulance to land to take the pedestrian, a 19-year-old man, to hospital in London. He has life threatening head injuries.
Police are endeavouring to re-open the road as soon as possible.