SANTA BARBARA, Calif. -

Traffic backed up for miles on the U.S. Route 101 northbound highway Thursday morning.

Bumper-to-bumper traffic stretched from Santa Barbara all the way to Ventura due to Wednesday's fatal accident.

"The driver merged on driving the wrong way on the northbound 101 state Route 150 offramp," said CHP Officer Jonathan Gutierrez.

At 10:40 Wednesday night a white Mustang entered the highway the wrong way in Carpinteria and collided head-on with a big rig.

"The white Ford Mustang was flipped over due to the collision and landed on its roof. The driver of the Mustang was pronounced deceased at the scene," said Gutierrez.

It's still not determined if drugs or alcohol played a factor. The driver of the big rig was not injured. Twenty gallons of diesel fuel spilled on the highway. All lanes on the northbound side were closed for more than seven hours, but the backup of traffic lasted much longer.