1. To facilitate the interpretation of signals, an inscription may be added in a rectangular complementary panel placed below them or inside a rectangular panel containing the signal.
2. Exceptionally, when the competent authorities deem it appropriate to specify the meaning of a signal or a symbol or, with respect to regulatory signals, limit its scope to certain categories of users of the road or to certain periods, and the necessary indications by means of an additional symbol or figures in the conditions defined in the official catalogue of traffic signs, an inscription will be placed below the sign, in a rectangular complementary panel, without prejudice to the possibility of replacing or completing those inscriptions by means of one or several expressive symbols placed on the same plaque.
In the event that the sign is placed on a fixed or variable message poster, the inscription that refers to it may be located next to it.