18-wheeler falls 30 feet off an overpass in north Harris County

HOUSTON, Texas (KTRK) -- The Grand Parkway at Northcrest is back open after an 18-wheeler went flying off an overpass in north Houston.

Eyewitness News captured video of the big rig that fell 30 to 40 feet off the side of the Grand Parkway.

The truck landed upright and its trailer was sprawled across the road.

The driver of the truck was not injured, and no other vehicles were involved.

Investigators say it's not clear how the driver went off the road.