Indiana Code Title 9. Motor Vehicles § 9-21-5-8

Sec. 8. (a) Whenever the Indiana department of transportation within the department's jurisdiction or a local authority within the authority's jurisdiction determines, based on an engineering and traffic investigation, that slow speeds on a part of a highway consistently impede the normal and reasonable movement of traffic, the Indiana department of transportation or local authority may determine and declare a minimum speed limit below which a person may not drive a vehicle except when necessary for safe operation or in compliance with law.  A limit determined under this subsection and declared by appropriate resolution, regulation, or ordinance becomes effective when appropriate sign or signals giving notice of the limit of speed are erected along the affected part of a highway.

(b) A person who fails to maintain a minimum speed limit established under this section commits a Class C infraction.