Barker was driving a black Mercedes in Calabasas when witnesses say he was making a left turn and a school bus smashed into him ... the bus was also in the midst of a turn.

Law enforcement sources tell TMZ no children were on the bus and Travis was not at fault.

After the crash Travis was walking around and did not appear seriously injured, although he did seem dazed. There were passengers in Travis' car, including his son. We do not know their condition, but the collision was serious enough for Barker's air bags to deploy.

The accident has created a mess on the street and police and other emergency vehicles have blocked off the area.