A 63-year-old woman suffered serious fractures and internal injuries in a head-on road smash.
The woman, from Louth, had to be cut free from her silver Kia Picanto after a collision with a silver Audi TT.
Emergency services were called to the A157 at West Barkwith at 5.15pm yesterday.
The Kia driver is being treated at the Queens Medical Centre in Nottingham.
The Audi driver, a 31-year-old Lincoln woman, received treatment for minor injuries.
Police closed the road until 11pm.
Anyone who saw the collision or who saw the vehicles prior to the incident should call the Collision Witness Hotline on 01522 558855.