The incident happened on the M11 near Chigwell (credit: Google Maps)
Two vehicles, a BMW and Ford Focus, collided between junctions five and six around 1pm yesterday afternoon.
The Focus driver was taken to hospital with injuries believed to be life-changing.
Three others, the BMW driver and two passengers, were treated for minor injuries.
Police are appealing for anyone who witnessed the incident or the moments before it.
Anyone with dash cam footage or information are asked to make a report on the Essex Police website.
Alternatively you can call 101 or independent Charity Crimestoppers, completely anonymously.
Refer to incident 760 of 9 August, when reporting any information.
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Tags: Chigwell, Debden, Epping