(a) General rule.--Simultaneous flashing of the two front and two rear signal lamps shall indicate a vehicular traffic hazard. The driver of a motor vehicle equipped with simultaneous flashing signals shall use the signals when the vehicle is stopped or disabled on a highway, except when the vehicle is stopped in compliance with a traffic-control device or when legally parked. Drivers of other vehicles shall exercise extraordinary care in approaching, overtaking and passing a vehicle displaying vehicular hazard warning signals.
(b) Use outside business and residence districts.--Outside of a business or residence district:
(1) The driver of a motor vehicle or combination equipped with simultaneous flashing signals shall use the signals when the vehicle is unable to maintain a speed of at least 25 miles per hour because of weather, grade or other similar factors or is unable to maintain a speed consistent with the normal flow of traffic.
(2) The driver of a bus equipped with simultaneous flashing signals shall use the signals when the bus is stopped with one or more wheels on the roadway between dusk and dawn for the purpose of receiving or discharging passengers.
(c) Use below minimum speed limit.--The driver of a motor vehicle or combination equipped with simultaneous flashing signals shall use the signals when the vehicle is not maintaining at least the minimum speed established in accordance with the provisions of section 3364 (relating to minimum speed regulation).