Indiana Code Title 9. Motor Vehicles § 9-21-8-10.5

Sec. 10.5. (a) When approaching or driving through a roundabout, a person driving a vehicle shall yield the right-of-way to the driver of a vehicle with a total length of at least forty (40) feet or a total width of at least ten (10) feet that is driving through the roundabout at the same time or so closely as to present an immediate hazard, and shall slow down or stop if necessary to yield.  However, this subsection does not require a person who is driving a vehicle through a roundabout to yield the right-of-way to the driver of a vehicle with a total length of at least forty (40) feet or a total width of at least ten (10) feet that is approaching the roundabout.

(b) If two (2) vehicles each having a total length of at least forty (40) feet or a total width of at least ten (10) feet approach or drive through a roundabout at the same time or so closely as to present an immediate hazard, the driver on the right shall yield the right-of-way to the driver on the left, and shall slow down or stop if necessary to yield.