Motorists faced rush-hour delays in The Deepings area after a spate of accidents in villages along the A15 corridor.
All three crashes happened on Thursday morning, the most serious when a 33-year-old man on a bicycle was in collision with a Vauxhall Astra on King Street, West Deeping.
It happened at about 7.10am and the cyclists was taken to Peterbrough City Hospital with serious head, back and leg injuries before being transferred to Addenbrookes Hospital, Cambridge.
The road was closed for almost five hours and didn’t fully reopen until 12 noon.
Anyone who saw the accident should call Lincolnshire Police’s collision hotline on 01522 558855.
Meanwhile, a Peugeot 306 and Ford Ka collided on nearby King Street, Langtoft, just after 9am and paramedics treated drivers of both vehicles for minor injuries.
Finally, police were forced to close Bourne Road, Folkingham, for several hours after a BMW X5 and Peugeot 206 collided just before 9am.
A number of casualties were treated for minor injuries by paramedics, while firemen cleared up diesel spillage and recovered both vehicles.
The road was finally cleared at about 11.20am.