A jack-knifed big rig has been cleared and the Southwest Freeway northbound lanes have reopened between the 610 West Loop and Weslayan.

The disabled 18-wheeler had been blocking all lanes of Highway 59 north and traffic was only getting by on the right shoulder.

Houston police tell Local 2 the accident happened at around 3:50pm when the big rig hit the concrete median.

A heavy duty wrecker arrived on scene and the scene was cleared shortly before 6pm.