"Today we mourn the loss of one of our own in this tragic incident. Our thoughts and focus are on supporting the family at this time. This is an unfortunate reminder of how dangerous highway work can be," said Caltrans Director Malcolm Dougherty in a statement.
The incident happened near the Red Rover Mine Road exit. Caltrans said 57-year-old Jorge Lopez of Sylmar was working when he was killed while standing outside his vehicle.
"Anne and I were saddened to learn of the death of Jorge Lopez, who worked each day to make our California roads safer. We extend our deepest sympathies to his family, friends and many colleagues who are mourning this tragedy," Gov. Jerry Brown said in a statement.
Two other Caltrans employees who were driving behind Lopez witnessed the accident but were not injured.
Caltrans worker killed after being struck by tanker truck on SB 14 Fwy just south of Crown Valley Rd. in Acton. pic.twitter.com/UyAreQNRMn— Marc Cota-Robles (@abc7marccr) September 1, 2016
Lopez, an electrician who worked for Caltrans for 16 years, was the 185th Caltrans employee to lose his life on the job.
Multiple southbound lanes were shut down for the accident investigation, causing a significant backup.
The governor's office said Capitol flags will be flown at half-staff to honor Lopez, who is survived by his wife Leticia and three adult children.