After a crash at 7.19am this morning the A17 Leadenham by-pass was closed for five hours, re-opening to traffic at 12.20pm.
The incident involved a silver VW Golf estate car colliding with a blue VW Tiguan 4 x 4.
The driver and lone occupant of the Golf, a 23-year-old Rotherham man, was trapped for some time and released by the Fire and Rescue service.
He was taken to Queens Medical Centre at Nottingham by air ambulance with serious leg injuries and a fractured wrist.
It is not thought that anyone else is seriously hurt.
Anyone who witnessed the crash or who may have seen either of the cars being driven prior to it is asked to contact the Collision Witness Hotline on 01522 558855.