The collision involving a white coloured Ford Focus and a pedestrian occurred close to Holywood train Station shortly before 8pm.
The 16 year old male pedestrian remains in a critical condition in hospital.
Police are appealing for anyone who was travelling on the A2 last night and who witnessed the collision, or captured any footage on dashcam, which could assist the police investigation to contact local officers in Bangor on 101 quoting reference 1384 of 01/01/18.
Police are particularly keen to hear from anyone who may have dash cam footage of the collision.
The family of the young teen male are with him in hospital where he continues to receive treatment for his injuries.
The family have asked for privacy at this time.
A police spokersperson said: “We would like to take this opportunity to thank the members of the public who helped us with this appeal.”