Whether the safety slogan should be signed?

yes. The function of the signature is to clarify the unit that writes the propaganda slogan. The signature of the slogan should be concise. If the slogan is not rigorous or does not meet the standard, you can contact the unit that writes the slogan through the signature. The function of autograph is not only to explain the identity and time of the creator, but also to protect the copyright of the work and prevent others from copying it.