Upon conviction of a school zone speed violation, the operator of the motor vehicle shall be assessed a fine of double the amount prescribed by law outside a school zone. The signs, placed at the entrance of the school zone, shall warn of the doubled fines for speeding within a school zone. The signs shall also state that the doubled fines are applicable only during the times posted on the signs.
Ala. Code § 32-5A-185 (1975)