Complex sentence: In 2013, Moody's downgraded the company's debt to junk status due to low traffic revenues, raising the possibility that TxDOT might terminate its toll contract with the group.
Split into simpler sentences: In 2013, Moody's downgraded the company's debt to junk status due to low traffic revenues. If the difficulties persist, TxDOT could terminate its toll contract with the group.