(a) The operator of a vehicle described by § 547.503(b) or an explosive cargo vehicle that is disabled, or stopped for more than 10 minutes, on a roadway outside an urban district or on a roadway of a divided highway when lighted lamps are not required shall display two red flags that comply with § 547.502.
(b) If traffic on the roadway moves in two directions, one flag shall be placed approximately 100 feet to the rear and one approximately 100 feet ahead of the vehicle in the center of the lane occupied by the vehicle.

(c) If traffic on the roadway moves in one direction, one flag shall be placed approximately 100 feet and one approximately 200 feet to the rear of the vehicle in the center of the lane occupied by the vehicle.