(a) If a transportation project of an authority severs a property owner's real property, the authority shall pay:
(1) the value of the property acquired; and
(2) the damages, if any, to the remainder of the owner's property caused by the severance, including damages caused by the inaccessibility of one tract from the other.
(b) At its option, an authority may negotiate for and purchase the severed real property or any part of the severed real property if the authority and the property owner agree on terms for the purchase. An authority may sell and dispose of severed real property that it determines is not necessary or useful to the authority. Severed property must be appraised before being offered for sale by the authority.