It happened about 5:40 p.m. in the 2200-block of Lystra Road, which is just south of Chapel Hill.
Troopers said a Honda Accord with four people inside ran off the road, overcorrected, and then hit a tree on the other side of the road.
All four people inside the car were taken to UNC Hospitals. Troopers said 19-year-old Chelsea Cooper was driving and suffered the worst injuries. She was in ICU.
The passengers were 41-year-old Elizabeth Brown, 14-year-old Jason Barnes, and 16-year-old Katie Barnes. Brown is Jason and Katie's mother.
According to officials, speed is likely a factor in the crash. The accident happened in a 45 mph zone, but speed estimates have not been determined.