Southbound lanes of I-15 were closed near 8500 South Wednesday after a loaded concrete truck went out of control and flipped on its side. The driver, Thomas T. Tucker, was cited for driving an overweight truck, and state highway officials are investigating whether a mechanical failure or other causes contributed to the one-vehicle accident, said Utah Highway Patrol trooper Brent Dunlap. Traffic was restricted to one lane for three hours after the 11:30 a.m. crash. The southbound lanes of the freeway were closed completely for about 30 minutes while crews cleaned up the spill.