The collision was reported on westbound Highway 4 just east of Port Chicago Highway about 8:25 a.m., CHP Officer John Fransen said.
One student was riding on the bus, but no injuries were reported, Fransen said.
A Sig-alert was issued at 8:35 a.m. It was lifted at 9:25 a.m., but the Port Chicago Highway on-ramp remains closed.
The collision remains under investigation, Fransen said.
Traffic was diverted to state Highway 242, just west of Port Chicago Highway, during the closure.