An 18-wheeler lies on its side along westbound Interstate 20, near the Iowa Boulevard overpass, Monday night. The tractor trailer, hauling a 56-ton steel I-beam, struck an overpass guard rail just after 5 p.m., shutting down both westbound lanes for about five hours, said Vicksburg police Sgt. Jackie Johnson. The driver, John Thomas Adams of Millbrook, Ala., was not injured, he said. The overpass was inspected last night by the Mississippi Department of Transportation, and at least one lane of the interstate was reopened around 10 p.m., Johnson said. More tests were to be done today.