(a) A toll project entity may establish a discount program for electronic toll collection customers.  The program must include free or discounted use of the entity’s toll project by an electronic toll collection customer whose account relates to a vehicle registered:

     (1)  under Section 504.202;

     (2)  under Section 504.315(g); or

     (3)  by a person who has received the Medal of Honor.

     (b)  The legislature may appropriate funds from the general revenue fund to a toll project entity to defray the cost of providing free or discounted use of the entity’s toll project under this section.