A 20-year-old man was critically injured when the car he was travelling in over turned on the M62 motorway near Knottingley.
It happened shortly before 8pm on Saturday on the westbound carriageway between junction 34 at Askern and junction 33 at Ferrybridge.
Police said the driver of the red Vauxhall Astra involved appeared to have lost control of the car, which overturned before coming to rest in a drainage ditch at the side of the motorway.
The driver and three other passengers were treated for non-life threatening injuries.
PC Peter Schofield, of the Southern Area Roads Policing Unit, said: “We would appeal for anyone who witnessed this collision or believes they may have seen the vehicle involved immediately prior to the collision to contact us.”
Anyone with information should call police on 101.