What is an AIP document in the Construction Industry?

Updated: Jul 30




The Approval In Principle (AIP) document outlines the concept for the design of the structure.

This will be used for most highway structures and incorporates the Technical Approval Schedule (TAS) which lists all the current British Standards and documents that are relevant to the design of highway structures.


According to BD2/12 (Document: Design Manual For Roads And Bridges (DMRB) ):

volume 1 - SECTION 1 - PART 1 - BD 2/12


HIGHWAY STRUCTURES: APPROVAL PROCEDURES AND GENERAL DESIGN APPROVAL PROCEDURES


Summary of what an AIP is


An AIP is a standard documentation required for any structure (e.g. Bridge, retaining wall, gantry, etc.) constructed in the civil engineering industry.


This document will include:

  • A description of the proposed structure

  • The category of the structure

  • Details of the road it is on or adjacent to

  • The proposed loading criteria

  • The proposed method of analysis of the structure

  • A schedule of applicable design standard

  • Requirements for road restraint systems (parapets and safety fences)

  • Headroom requirements

  • Details of other structural forms considered

  • Conceptual drawings (if applicable)


Details of any references from Standards and any other information required by the Technical Approval Authority to determine whether the proposed design and checking regime is robust and acceptable.



In theory, prior to commencing design, the AIP must be signed by the Technical Approval Authority. In practice, programme constraints dictate that some design is carried out prior to obtaining a signed AIP, though this is at the designer/client's risk as the Technical Approval authority could require a change to the design process, resulting in the need to revisit the design.


Busy Highway Intersection

The History of the AiP


In the early 1970s, failures at Yarra (Australia), Milford Haven (Pembrokeshire, Wales), Koblenz (Germany) and over the Danube (Austria) occurred during erection. </