Indiana Code Title 8. Utilities and Transportation § 8-1-3-2

Sec. 2.  (a) If a petition for rehearing is filed with the commission by a party to the proceeding before the commission, within the time allowed by the rules of the commission, the commission must rule on the petition within a reasonable period of time after the filing of the final pleading filed in support of or opposition to the petition.  If the commission fails to rule on the petition within a reasonable period of time, the petitioner may bring an action for mandate under IC 34-27 to compel the commission to make the ruling.  However, notwithstanding IC 34-27 or any other law or rule, the action for mandate may only be filed in the court of appeals.  For the purposes of IC 1-1-1-8, if any part of this subsection is held invalid, the entire subsection is void.

(b) If a petition for rehearing is filed with the commission by any party to the proceeding before the commission, within the time allowed by the rules of the commission, and prior to the filing of the commission record with the clerk of the supreme court, the right to appeal under this chapter terminates thirty (30) days after the determination by the commission on such petition for rehearing.  The appeal shall not be submitted prior to that determination of the petition for rehearing, and the decision of the commission on the petition shall not be assigned as error unless the final decision, ruling, or order of the commission is modified or amended as a result of the petition without further hearing ordered.