Big rig overturned on highway 99 | News - KCRA Home Big Rig Overturned, Blocking Traffic | KTXL FOX40 The accident is not currently being labelled a hazmat issue and CHP says they are most concerned about the toxic material in the truck. CHP said it’s unclear why the accident happened. He said the driver could have fallen asleep, or it could have been a mechanical issue. Fire crews had to break the window to get the driver out. He was conscious, but complained of pain. He also suffered minor injuries and was taken to a hospital.