The crash was first reported on Houston Transtar around 12:30 a.m.
All lanes had been blocked westbound, and cleanup efforts had also blocked the two left lanes going eastbound. All mainlanes reopened at about 6:40 a.m.
Even after the big rig had been towed away, drivers were still experiencing at least 30-minute delays.
Transtar cameras showed the 18-wheeler flipped on its side.
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