The accident happened Friday evening on HWY-150 near CR-590 West.
Indiana State Police tell us this section of roadway was recently resurfaced, causing about a four inch difference in surface levels.
Troopers say the moped driver was trying to travel from the shoulder onto the paved portion of the road when he lost control and crashed.
Tony Poe and Rachelle Wininger, both of French Lick, were taken to hospitals with serious injuries.
We're told neither of the riders were wearing helmets.
Their conditions are currently unknown.