WALNUT CREEK -- A car flipped over in a crash, and a big rig trailer caught fire during a turbulent Wednesday morning on Contra Costa County highways.

Both incidents caused the California Highway Patrol to issue brief SIG alerts for severe traffic, but the scenes were cleared quickly.

The car that flipped did so just after 9 a.m., while it was on northbound Interstate 680 just south of the Ygnacio Valley Road exit, CHP Officer Kevin Bartlett said. The driver exited the car without assistance and appeared to have only minor injuries, Bartlett said. Rain created slick roads, but the CHP did not say immediately whether weather was a factor in the wreck.

That crash blocked one lane of I-680, and the CHP issued a SIG Alert at 7:21 a.m. They canceled it 20 minutes later.

About an hour later, the big rig trailer went ablaze on eastbound Highway 4 near the Bailey Road exit. The response momentarily blocked all lanes, and the CHP issued a SIG alert at 8:55 a.m., Officer Ron Simmons said. Information about what caused the fire and how soon fire crews put it out was not available immediately, nor did the CHP say whether there were any reports of injuries.

Authorities reopened all lanes within minutes, and the CHP lifted the alert at 9:09 a.m., Simmons said.

Check back for updates.

Contact Rick Hurd at 925-945-4789 and follow him at Twitter.com/3rderh