DUBLIN -- A Livermore pediatrician was killed in a car crash Friday morning after he drove his Jaguar beneath a tractor-trailer while driving on Interstate 205 in Tracy, the California Highway Patrol said.

Dr. Robert Barnett, 59, of Dublin, was in the fast lane headed east about 7:20 a.m. when he suddenly made an abrupt right turn and collided with a tractor-trailer two lanes over, CHP Officer Adam Shelton said. The 2000 Jaguar drove all the way underneath the big rig's trailer but did not completely clear it, Shelton said, and Barnett came to rest on the shoulder about a half mile east of Mountain House Parkway.

Barnett was pronounced dead at the scene, Shelton said. The driver of the big rig, 49-year-old Jorge Ibarra, of Riverside, was uninjured in the crash.

While investigators do not know why Barnett abruptly veered across lanes, Shelton said neither speed, drugs nor alcohol are thought to be factors in the crash.

"At this time, we don't know why he made the unsafe lane change," Shelton said. "The reason why he made that turn is under investigation."

No charges will be filed against Ibarra, who was also traveling alone when he was hit. The cause of the crash remains under investigation pending results from an autopsy and toxicology tests.

Barnett, a practicing pediatrician of 31 years, managed the pediatric department at the Kaiser Permanente campus in Livermore, according to a Kaiser Permanente website. He began his career as a resident at UC San Diego before moving to the Bay Area, where he became a chief resident at Children's Hospital Oakland before moving to Kaiser Permanente.

"I became a pediatrician because children are uniquely capable of overcoming their problems," Barnett wrote in his biography for Kaiser Permanente. "They are, at the same time, usually innocent of the cause and are rarely at fault for their problems. "

Contact Erin Ivie at eivie@bayareanewsgroup.com. Follow her at Twitter.com/erin_ivie.