The collision happened on the southbound section of the motorway near Winchburgh, at about 6.10pm on Tuesday.
Divisional Road Policing Inspector, Richard Latto, said: “A silver coloured motorvan left the carriageway at the overbridge to the B8020, Winchburgh to Newton Road, resulting in serious injuries to its driver.
“At this time we are working to establish exactly what has happened during this incident and we would urge motorists or members of the public who were in the area at the time and witnessed the incident who have not yet spoken to police to come forward.
"In addition, vehicles with dash-cam footage, which may be able to assist with this inquiry should also get in touch.
“Anyone with information can contact Police Scotland via 101 and quote incident number 3036 of 28th of August."