Ala. Code § 11-11-4

As security for the payment of the principal of and interest on warrants issued under the provisions of this chapter, the issuing county is authorized to assign and pledge for the benefit of the holders of the said warrants so much as may be necessary for such purpose (which may be all) of the proceeds of the county’s share of the highway gasoline tax. All such pledges shall take precedence in the order in which they are made.