A tractor-trailer jackknifed Thursday on the eastbound Pomona (60) Freeway connector to northbound Interstate 15 in Eastvale, forcing a closure of the transition.
The trailer half of the big rig went onto its side about 11 a.m., according to the California Highway Patrol.
Santa Ana winds were blowing about 20 to 25 mph in the area at the time, possibly causing the driver to lose control, according to reports from the scene.
The trucker was not injured, and no other vehicles were involved.
CHP officers completely closed the transition about 11:15 a.m. A SigAlert was issued due to the closure and ensuing traffic jam.
It was the second semi to overturn at the freeway interchange within an hour. The other occurred at the southbound Interstate 15 to eastbound 60 connector, according to the CHP. That, too, resulted in a full closure of the transition bridge.