New structure

 

Overview of new MCHW structure

The old MCHW was structured in 7 volumes, whereas the updated MCHW is structured around 3 document sets, see figure 1. In redrafting the MCHW, specific attention was given to allocate content in the relevant document set.

Illustration of mapping of old volumes 0 to 6 to new document sets and DMRB, with MCHW publication outputs i.e. country-specific versions and WSR templates

Figure 1 – New MCHW document set structure

Criteria for moving content

  • If the content covered products, materials or activities related to products and materials relevant to construction, it moved to the new Specification for Highway Work (SHW) documents.
  • If the content covered the information that needs to be included in the work specific requirements in order to specify fully relevant objects or materials, it moved to the new Instructions for Specifier (IfS) documents.
  • If the content covered a design activity and/or design decision, it moved to the DMRB documents.
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What happened to the old volumes

  • Old Volume 0 has been generally withdrawn without replacement as either obsolete or no longer required, with some aspects transferred to GP 110 “Introduction to the MCHW” and GC 100 “Introduction to the Specification for Highway Works”.
  • Old Volume 1 has been reviewed and most of the content has been updated and migrated to the new Specification for Highway Work (SHW) documents.
  • Old Volume 2 has been reviewed and most of the content has been updated and migrated either to the new Instructions for Specifier (IfS) documents where relevant to contract specifiers, or to the DMRB where covering content relevant to designers.  Follow the link for more information (Notes for Guidance: from compiler guidance to specifier instructions).
  • Old Volume 3 has been reviewed and it is no longer a separate volume; where deemed still necessary following their review, the Highway Construction Details have been updated and moved to: relevant DMRB documents as illustrative figures; SHW documents where relevant to construction; the Operational Technology Standards Library (OTSL) for traffic technology items. Follow the link for more information (Highway Construction Details).
  • Old Volume 4 has been reviewed and content has been updated and split into individual documents covering Method of Measurement for Highway Works (MMHW) complementing the new SHW documents.
  • Old Volume 5 has been reviewed and it is no longer a separate volume; content has been updated and migrated to the new SHW where relevant to constructors, to the IfS documents where relevant to contract specifiers, and to the new MMHW documents as appropriate.
  • Old Volume 6 is no longer a separate volume; relevant documents have either been withdrawn as obsolete or moved to the DMRB as appropriate.

See Old to new MCHW for a mapping of old to new documents.

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New document sets

The Specification for Highway Work (SHW) has been significantly revised to provide standardised and clear requirements for constructors, which can be mapped to specific objects, materials, or activities related to objects and materials including workmanship, verification and documentation requirements.

The old Notes for Guidance volume has been significantly streamlined and replaced by the Instructions for Specifiers (IfS) documents. These will display specifier instructions underneath the corresponding constructor requirement for clarity and ease of use. The old contract specific appendices have been replaced by Works Specific Requirements (WSR) derived from the specifier instructions contained in the main text. WSR templates have been made available in open-source files to give the specifier a clear, consistent, and complete format to support the development of a contract-specific specification.

The Method of Measurement for Highway Works (MMHW) is now a stand-alone set of documents, aligned with the SHW content. The Library of Standard Item Descriptions for Highway Works is now provided in an open format file on the Standards for Highways website.

See New to old MCHW for a list of new MCHW documents.

Three boxes showing the constituent parts each of the Specification for Highway works, the Instructions for Specifier and the Method of Measurement for Highways Works

Figure 2 – The updated MCHW document sets

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New document numbering system

The update to the MCHW has resulted in existing documents (series) being subdivided or consolidated, therefore the numbering system needed to be reviewed.

In RIS1, National Highways set up a matrix for technical standards and specifications, which provides the framework to identify document codes and numbers based on discipline and life-cycle stages, see Figure 3. This matrix was applied to the DMRB.

MCHW documents have now been renumbered to become consistent with the wider NH technical standards matrix numbering system. This will mean that the old MCHW series numbers will no longer be used. This approach will ensure consistency with the DMRB numbering system.

The mapping of old to new MCHW documents is available to support the transition from the series system to the new coding system.

Table showing document numbering matrix for MCHW and DMRB, based on life cycle stage and discipline

Figure 3 – Document numbering matrix for technical standards and specifications

SHW numbering system

SHW documents now have a new code given by the combination of <discipline><construction stage> and <number>, for example:

  • GC 100 covering a general construction document
  • LC 120 covering a sustainability construction document
  • CC 400 covering a civil construction document
  • TC 101 covering a technology construction document

IfS numbering system

IfS document code is given by the combination of <discipline><contract preparation stage> and <number>, which mirrors the corresponding SHW document, for example:

  • GP 100 covering the instructions for specifier for a general construction document
  • LP 120 covering instructions for specifier for a sustainability construction document
  • CP 400 covering instructions for specifier for a civil construction document
  • TP 101 covering instructions for specifier for a technology construction document

MMHW numbering system

MMHW documents now have a new code given by the combination of <discipline><construction stage> <number></MMHW>, for example:

  • LC 120/MMHW covering method of measurements for a sustainability construction document
  • CC 400/MMHW covering method of measurements for a civil construction document
  • TC 101/MMHW covering method of measurements for a technology construction document
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Notes for Guidance in Volume 2 – from compiler guidance to specifier instructions

The old Notes for Guidance documents contained significant design information which belongs in the DMRB. An extensive rationalisation of content has been undertaken to move design content into the DMRB and retain only content relevant to compile the contract-specific specifications (i.e. the specifier instructions) in the MCHW.

Specifier instructions do not give guidance on design activities or decisions, rather they present the outcome of the design into a clear set of instructions, which can be translated into works specific requirements. Guidance on design activities or decisions is relevant to the designer, thus it needs to be provided in the DMRB.

By removing guidance on design decisions, hence interpretation, and simply providing instructions to compile the specifications, we will open the door to automating the process of populating contract-specific specifications. BIM is changing the way information is produced and we want to respond to industry change by making the future MCHW compatible with asset information strategies, whilst supporting our vision for digital roads.

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Highway Construction Details in Volume 3 – from standard drawings to illustrative figures

There were almost 500 drawings in old Volume 3 (see drawings’ list). An extensive review of all Highway Construction Details (HCD) was undertaken and a few issues were identified including:

  • limited applicability of the HCDs without project specific adaptation (i.e. the drawings contained variable dimensions to be defined based on the design output);
  • many HCDs contained textual requirements and advice, not always aligned with relevant SHW clauses, difficult to maintain and out of date;
  • confusion over design responsibilities by using standard details.

To address these issues, a decision was made to move drawings alongside the requirement / advice they represent and present them as illustrative figures in the relevant set (DMRB, MCHW and OTSL). Moreover, it was decided that such figures should not contain textual requirements or advice.

Practical implications of such decisions are listed below:

  • Current Volume 3 drawings have now disappeared; old versions of the drawings are still available for legacy works, existing contracts, future maintenance contracts.
  • Each Volume 3 drawing has been reviewed to check its relevance and to identify an appropriate location in the DMRB, MCHW or OTSL.
  • Most of the Volume 3 drawings are now figures in the DMRB as providing information relevant to the designer.
  • Textual requirements and advice contained on drawings migrated to relevant DMRB, SHW or OTSL documents and have been updated as needed.
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