She was hit by an HGV being and suffered a broken pelvis, broken leg, and multiple other injuries, at around 12.30am on Friday.
A young woman is fighting for life after jumping from a moving car into the path of a oncoming lorry on a busy motorway. The 22-year-old was in the front passenger seat of a Fiat Punto travelling north on the M55 when she opened the door and threw herself out, police said.
She was taken to Royal Preston Hospital where her condition was initially described as serious but not life threatening.
Police later said she was fighting for life. The 38-year-old lorry driver was unhurt.
A spokesman for Lancashire Police said it is not believed the woman was being held against her will, but said it was unclear why she jumped.
Sgt Malcolm Bell from the Road Policing Unit said: "This incident has left a woman with serious injuries and we would appeal to anyone who may have witnessed what happened and has not yet spoken to us to get in touch as soon as possible."