A motorcyclist, who died in a collision on the A6 near Rowsley on Sunday July 7, has been named as Richard McSherry, from Glossop.
The family of Mr McSherry, who was 46, are being supported by specialist officers.
The crash betweenen a grey Audi A6 estate and a black Aprilia motorbike, happened just before 4.30pm.
Officers would like to identify the rider of a dark-coloured Suzuki Hayabusa which was seen travelling along the A6 from Rowsley around the time of the collision. This person may have witnessed the incident, and may be able to help enquiries.
Witnesses who saw the bike, or were driving in the area at the time are asked to contact Derbyshire Police and quote reference number 19*353568 in any correspondence.
Send a private message to /DerbyshireConstabulary; complete the online contact form www.derbyshire.police.uk/Contact-Us, or phone 101.
You can also call Crimestoppers anonymously on 0800 555 111.