Officers are asking for anyone who saw a collision on Somerby Hill yesterday evening to contact them.
The road was closed around 4.30pm on Tuesday 15 September 2015 following a collision with a pedal cycle and a black Peugeot 307 car.
Both vehicles were travelling out of Grantham towards Old Somerby roundabout when they collided.
The pedal cyclist, a 51-year-old Sleaford man suffered what are described as very serious injuries and was taken to the Queen’s Medical Centre in Nottingham.
The male driver was not injured.
The road was re-opened at 8.30 pm.
The Investigating Officer has asked for anyone who saw the collision to call the Collision Witness Hotline on 01522 558855 quoting incident 280 of 15 September.