Update of Vol 7 in The Design Manual for Roads and Bridges (DMRB)

Over time, the DMRB has expanded to cover many topics but it has become unwieldy; the old version contained over 10,700 pages, 294 documents, and the average age of documents was around 15 years. TRL has updated the DRMB in accordance with the Manual for the Development of Documents (MDD), to make it easier to use and maintain.

Published on 13 March 2019

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The Design Manual for Roads and Bridges, originally published in 1992, is a compilation of the current standards, advice notes and other published documents relating to the design, assessment and operation of trunk roads (including motorways) in the United Kingdom.

TRL has been directly involved in the writing and production of Standards for decades and it is our research that underpins a large percent of the content of the current DMRB, including the Standards.

Over time, the DMRB has expanded to cover many topics but it has become unwieldy; the old version contained over 10,700 pages, 294 documents, and the average age of documents was around 15 years. 

A review of the structure and content of the DMRB resulted in the creation of a Manual for the Development of Documents (MDD): this sets out the procedures, processes, instructions and advice on the development of new documents as well as the updating of existing documents.

The new philosophy embodied in the MDD aims to achieve the following:
  • Enhanced efficiency and innovation in design – enabled by a DMRB that is clearer, quicker, up to date and easier to use, with fewer Standards, clearer requirements and better advice resulting in better design solutions;
  • Greater efficiency in the production and maintenance of the DMRB;
  • Fewer departures from Standards; and
  • Fewer Compensation Events under Clause 17.1 of the NEC for inconsistencies in the Works Information.
In 2018 TRL began an overhaul of the existing Volume 7 (Pavements) of the DMRB for Highways England. The new document has just been released.  TRL have completely re-structured the documents to make a clear distinction between the ‘Assessment’ and ‘Design’ stages of the process. As well as incorporating the latest developments in materials, pavement design and innovative assessment techniques, the updates have led to a significant reduction in the number of documents (from 16 Standards and 5 Interim Advice Notes to 10 new Standards) and a dramatic reduction in page count. 

Many of the new pavement assessment approaches introduced within the replacement documents are specifically designed to improve both efficiency and safety. Some of the key improvements and innovations introduced in Vol 7 are as follows: 

  • New requirements and advice covering the collection of surface and structural condition data at traffic-speed, reducing the need for closures and reducing exposure of road workers to risks
  • Increased emphasis on the use of high-quality images collected at traffic-speed for undertaking assessment of visual defects.
  • New network-level methods and thresholds for routinely assessing the condition of concrete pavements.
  • New requirements and advice for determining the suitability of surfacings for receiving preventative maintenance treatments.
  • Improved processes for planning and reporting pavement maintenance investigations that maximise the use of existing condition data and minimise closures.
  • Pavement designs incorporating Roller Compacted Concrete that will lead to increased efficiency for new pavements.
  • A new design certification process that will facilitate improved technical governance of the pavement elements of Major Project schemes.
  • New requirements for designing surfacings which will enable significant efficiencies from reduced usage of scarce high Polished Stone Value (PSV) aggregates.  

TRL did not work in a vacuum. Vital to the success of the re-write was achieving buy-in to the new Standards required members of the TRL team to engage closely with over 100 stakeholders representing a wide range of views from across the highways industry. This required extensive consultation and communications with industry groups as well as a series of peer review workshops with representatives from across Highways England and from Scotland, Wales and Northern Ireland who are also adopting the new documents. 

The overall objective of the re-write of the new DMRB is to improve the usability, structure and content. The structure of the new documents is a better fit with the asset lifecycle approach that is badged within Highways England as “Future DMRB”. 

The new version includes new material on:

i.    Safety
ii.   Quality
iii.  Resilience, including for the effects of climate change
iv.   Innovation and whole life performance
v.    Overseeing Organisation “obligation” including changes as a result in the change in status from Highways Agency to Highways England and additional Devolution to Scotland, Wales and Northern Ireland
vi.   Equality Issues
vii.  Sustainability

There are also significant overlaps and interactions between the different Standards, so the overall review takes account of changes to other Standards.

The 2020 edition of DMRB is very different. Most noticeable to users will be the following features across the whole Manual:
  • Standards are to be kept up to date with a maximum review cycle of five years. This will allow them to more quickly incorporate new technologies, new processes and new materials.
  • Requirements have been drafted using consistent language which set out clearly the responsibilities of users.
  • A more structured format and style has been used that clearly distinguishes between requirements and advice.
  • Unnecessary advice has been removed; only advice that assists users to fulfil requirements has been included.
  • Where possible, and in line with best practice, requirements are less prescriptive and more performance based. The requirements are clear on the performance expectation that the requirement is seeking to address.
  • The structure of the Manual follows an asset lifecycle, with clear sections allowing users to quickly locate the information they require.
  • The main Standards are specific to Highways England. National Application Annexes (NAAs) have been used to allow devolved administrations to set their own modifications and adaptations of requirements and advice.

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