Four people were taken to hospital after an accident on the M62 which left the motorway closed in both directions.
The accident happened at about 3.45pm between J33 (Ferrybridge) and J34 (Whitley Bridge) on the westbound carriageway.
Eyewitnesses reported seeing the car swerving to avoid another vehicle before rolling down the embankmennt. Children were said to have been inside the car.
Initially both sides of the road were closed but the eastbound carriageway was reopened around 6pm.
The westbound carriageway, affecting traffic travelling towards Huddersfield, remained closed.
Insp Clive Turner from North Yorkshire Police said it was believed just one vehicle was involved in the collision, before coming off the motorway.
Four people were injured and were taken to hospital, some of them by air ambulance.
Police at the scene were investigating, he added.
Meanwhile a second serious accident happened near Rochdale, between J19 and J20.
Eyewitness Laura Bell said it looked like five cars were involved, and the accident had left the motorway gridlocked.
She said: "Five fire engines, three ambulances and tonnes of police. Looks like a five car pile up, looked horrendous. Hope the people are all okay. I felt sick driving past seeing babies' car seats."