If the department by rule requires a proposal guaranty as a condition of bidding for a contract, the guaranty may be in the form of:
(1) a cashier's check or money order drawn on a financial entity specified by the department; or
(2) a bid bond issued by a surety authorized to do business in this state; or
(3) any other method determined to be suitable by the department.
Official text of the Texas Transportation Code as published by the Texas Legislative Council.