The officer was found at about 3:30 a.m. still belted into the driver's seat on the 101 Freeway at the Van Nuys Boulevard off ramp. He was taken to the Ronald Reagan UCLA Medical Center, where he died.
Authorities with the California Highway Patrol said the officer's truck hit a guard rail, which pierced through his vehicle.
The officer was not immediately identified.
The cause of the crash was under investigation.
City News Service contributed to this report.