(a) The commissioners court shall apportion the assessed cost of improving a county road in accordance with the front foot rule which may vary among the assessed properties.
(b) To produce a substantial equality of burdens imposed in relation to benefits received, the commissioners court shall determine an assessment under this section in a just and equitable manner, keeping in mind the enhanced value to be gained by the abutting property and the property's owners because of the improvement.
(c) The commissioners court may not impose an assessment in excess of the enhanced value derived from the improvement by the property or the property owner.