One man suffered serious chest and leg injuries when the car he was travelling in came off the road at Small End near Friskney on the afternoon of Tuesday, July 19.
Three other men were also in the car when the incident happened at around 3.20pm, and all were taken to Pilgrim Hospital.
The Lincolnshire and Nottinghamshire Air Ambulance was in attendance.
All the men involved were from the local area, police have said.
Police said the collision happened on the road between the Parrot Sanctuary and Friskney Village.
The road was closed for several hours after the incident.