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CD 534 Guidance

The Design Manual for Roads and Bridges (DMRB) has recently been updated by Highways England (HE). For more than ten years, HA 104/09 (an ‘advice note’ within the DMRB) has been a key document for chamber tops and gully tops setting out procedures and denoting materials which Highway Authorities believe provide the best possible performance for installations in trunk roads and motorways.

This crucial HA 104/09 advice note has now been replaced by CD 534, a new Technical Regulation posted and referenced on the European Commission Technical Regulation Information System (TRIS) website. Both documents were produced by the HE in association with Transport Scotland, the Welsh Government and Northern Ireland’s Department of Infrastructure, and contain HE’s requirements for road chamber top and gully top installations on motorway and all-purpose trunk roads.

Whereas HA104/09 was ostensibly a stand-alone document, CD 534 contains ‘normative references’ (a document to which reference is made in the standard in such a way as to make it indispensable for the application of the standard) and must be read in conjunction with these as they contain some of the important requirements for chamber tops and gully tops that were previously explicit in HA104/09. Linked with CD 534 is Series 500 of Volume 1 of Highways England’s Manual of Contract Documents for Highway Works (MCHW).

Third Party Certification to BS EN 124 continues to be required

A key example is that of third-party certification of products. In clause 3.5 of HA 104/09, there is a requirement that chamber tops and gully tops be certified by one of the accepted UKAS certification bodies (e.g. BSI Kitemarked) to BS EN 124. There is no such clear requirement in CD 534. However, detailed study of the regulation and its cross references reveals that under its clause 1.6 the HE requirements contained in GG 101 shall be followed. G101 is the introduction to the DMRB and states ‘the requirements and advice given in DMRB documents are provided on the basis that the works are constructed in accordance with the MCHW’. Appendix B of the MCHW concerns ‘product certification schemes’ and it is here we find the requirement for a third-party certification scheme for BS EN 124.

Areas of difference between HA104/09 and CD 534

There are several areas where CD 534 differs from HA104/09 and some of these are summarised in the table below.

HA 104/09 requirement CD 534 Comment
3rd party certification Not explicit but captured in the linked appeddix B of the normative reference MCHW BS 7903 highlights consideration of Third-Party Certification. Also recommended by CEN Technical Committee TC165
Chamber top frame bearing pressure to be ≤ 2.1N/mm2 Not present explicitly BS 7903 refers to this requirement and HE’s Series 500 of the MCHW specifies bedding mortar strength properties which assume a maximum bearing pressure of 2.1N/mm2
Frames weighing more than 15kg must have provisions to allow balanced lifting Not present explicitly BS 7903 recommends this requirement (6.19)
Bedding mortar compressive (30N/mm2) and tensile strength (5N/mm2) Not present explicitly but captured in 507.24 of the normative reference MCHW BS 7903 expands on the importance of mortar specification under 5.5
Packing materials must be compatible with the mortar Not present BS 7903 expands on the importance of the compatibility of packing materials under 5.5
Chamber top PSRV of >45 or >60 depending on the site risk All Group 4 chamber tops to have a PSRV >60 Sensible to have PSRV tests carried out and confirmed by a UKAS accredited laboratory
Consider E600 chamber tops in certain circumstances E600 chamber tops must be used where the AADT LGV >1500 in each direction Introduces the requirement for E600 chamber tops in many roads

 

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