Firefighters had to use cutting equipment to rescue four people following a crash on the A1 northbound near Colsterworth.
Officers were called to the incident at 4.18pm on Saturday to free two women and a man from a silver Toyota Corolla and a woman from a white Volkswagen Touran.
The woman was taken to Queen’s Medical Centre in Nottingham after suffering a serious head injury. She remains in hospital in a stable condition.
The three people in the Toyota were taken to Lincoln County Hospital as a precaution for whiplash.
The road was closed and diversions were put in place while route was cleared.