The definition of a structure, for the purposes of TA procedures can be found in CG300 Section 3.
Highway structures will be categorised in one of four categories (0, 1, 2 or 3) depending on the criteria described in Section 3 to 6 of CG 300. The structures category shall be agreed with the TAA prior to design.
Category 1, 2 and 3 structures will require an Approval in Principle (AIP) document which shall be submitted to the TAA for acceptance.
Category 0 structure will not require an AIP document, though the parameters of the design must be agreed with the TAA prior to the commencement of any design.
A chartered engineer (CEng MICE, CEng MIStructE or equivalent) with experience in highway structures is required to sign-off the design of all highway structures. This qualification can be relaxed for Categories 0 and 1 with the agreement of TAA.