Fire fighters freed a woman from her car after it was involved with a collision with a lorry.
The incident happened at around 4pm between J33 Galgate and J34 Lancaster on the M6 Northbound.
Lancashire police say the woman - who was driving the car - has sustained serious head injuries and is receiving treatment at the Royal Lancaster Infirmary.
Three lanes of the motorway were closed for approximately two hours but now the final lane, that remained closed due to a fuel spill and so that the police accident investigation team could investigate, has been re-opened and traffic should be returning to normal.
Highways England said: “On the M6 Northbound J33 - J34 we’ve cleared the earlier accident and re-opened the last closed lane. Delays are slowly easing.”
A police spokesman said: “A woman was trapped in a car that had collided with a lorry.
“The fire service freed her from the car.
“The woman involved is believed to have sustained a serious head injury and is receiving treatment at the Royal Lancaster Infirmary.”
A spokesman for the fire service said: “We believe it was a car that ran into the back of a lorry.
“We cut the roof of the car off to free the person that was trapped in the car.”