Specifies requirements for tubular steel mast arms which are designed to support traffic signal lanterns and associated equipment above the road way. Also applies to joint-use mast arms which, in addition to supporting traffic signal lanterns, are designed to support road lighting luminaires. Designates three specific types of mast arm, viz. Types A, B and C, based on design and constructional considerations. Does not apply to traffic signal posts, requirements for which are specified in AS 2339.