Part time signals' Supplementary Plate - Post Mount Diagram 543.1 R2/RA2This supplementary plate is used alongside sign face traffic signals ahead 543 warning drivers that the signals only operate part time. This ensures that drivers understand that the signals are intentionally not activated, and not just out of order. This sign is available with text in different sizes (X heights), which size is required will depend on the road that the sign is to be installed on. For further guidance please see appropriate sections of