The single vehicle collision happened at around 3.40pm on Thursday 22 June 2017, when a Land Rover Discovery left the A61 near South Stainley between Ripon and Ripley and collided with a hedge and a telegraph pole.
The Discovery was travelling towards Ripley and Harrogate when the crash happened within the double bends just south of the Red Lion pub.
Officers have issued an appeal to trace the occupants of a small white car that was travelling in the opposite direction, towards Ripon behind an Alfred Hymas lorry.
They also want the occupants of three or four vehicles that were travelling behind the Land Rover, towards Ripley, to contact them.
It is hoped that these drivers or passengers may recognise the vehicle from the photographs issued from the scene of the collision. It is possible that they did not witness the crash but may have seen the Land Rover before it left the road. Offices still want them to come forward.
These vital witnesses and anyone else with any information are asked to contact North Yorkshire Police on 101, select option 2 and ask for Traffic Constable David Minto or email firstname.lastname@example.org
Please quote reference number 12170109365.
The occupants of the Discovery, a woman aged 19 and man aged 21, were taken to hospital. The woman was treated for serious injuries and has since been discharged from hospital. The man was treated for less serious injuries and discharged soon after.
Officers issued an appeal at the time of the collision and are now appealing for these specific witnesses to come forward.