An operator may not turn a vehicle to proceed in the opposite direction on a curve or on the approach to or near the crest of a grade, where the vehicle can not be seen by the operator of another vehicle approaching in either direction within 500 feet.   [PL 1993, c. 683, Pt. A, §2 (NEW); PL 1993, c. 683, Pt. B, §5 (AFF).]