A man died and a woman is in critical condition following a road collision on the A57 at Aston in the early hours of Sunday.
The incident happened at around 1am on Aston Way, near to the M1 junction on the carriageway going towards Sheffield.
A moped was involved in the crash, though it is currently unclear who the rider was.
Police believe the collision may have involved a second vehicle, which would probably have frontal damage.
They are appealing for the driver to come forward, or anyone who may have seen a damaged vehicle.