A representative for Utah Highway Patrol said the crash happened around 1:25 a.m. on southbound I-15 near mile marker 259, close to the Springville-Spanish Fork border.
Witnesses told troopers a car went off the right side of the road, hit a barrier, went back onto the road and got hit by another vehicle.
"We don't believe there was any alcohol or drugs at this point. She may have been a drowsy driver which brings up another point: when drivers are drowsy, they need to stay off the road, pull over, rest, whatever they need to do to make it safe for them and everyone else," said Sgt. David Rumfield, UHP.
UHP investigators are looking into why the car left the road.