Must a load that protrudes from the rear of a car be signalled?

If the load protrudes from the rear of a car, during the day, in clear weather and under normal visibility conditions, it must be signalled with a 50 by 50 centimetre panel, painted with alternating diagonal red and white stripes, placed at the rear end of the load so that it remains constantly perpendicular to the axis of the vehicle. If the load protrudes from the rear, between sunset and sunrise or in meteorological or environmental conditions that significantly reduce visibility, it must be signalled with the panel or panels indicated above, whose surface is reflective, and with a red light.