Durham Constabulary are appealing for information following a collision on the A19 southbound yesterday, Thursday, March 4, which left the road closed for eight hours between the A182 at Murton and the A1086 at Easington Hall Walks junction.
People who saw the crash or the vehicles involved in the lead up to it could help as inquiries get under way.
Police say a Volkswagen Golf and a Ford S-Max collided with each other and street furniture, resulting in significant damage to both of the vehicles.
The Volkswagen driver, a 29-year-old man, sustained serious injuries and was treated at James Cook University Hospital, with his vehicle left on its roof following the collision.
The driver and passenger of the Ford, a 22-year-old man and a 20-year-old man, sustained minor injuries and were taken to Sunderland Royal Hospital.
The North East Ambulance Service said it had assessed another patient at the scene before transporting those with injuries to hospital.
It sent eight resources in total to the crash site, including four crews from its Hazardous Area Response Team (HART), a specialist paramedic and two ambulance crews.
It also requesting support from the Great North Air Ambulance Service.
County Durham and Darlington Fire and Rescue Service sent appliances from Seaham, Peterlee and Wheatley Hill alongside a special rescue unit from its station in Bishop Auckland.
The crews used cutting equipment to cut one man free from one of the cars and the service left the incident just after 8pm.
Highways England also attended as it worked alongside the emergency services and helped clear the route before it was safe to reopen it to traffic.
Durham Constabulary has asked anyone who witnessed the collision, or who may have seen the vehicles prior to the incident, to contact the force on 101, quoting reference number 340 of March 4.