Road Note 39 is a guide for the design of surface dressing used on roads throughout the United Kingdom (it is NOT prepared as, nor should it be used as, a specification). This Seventh Edition of the Road Note is produced by a Panel representing all sides of industry, with the Chairman and Secretariat provided by the Road Surface Treatments Association and TRL Limited respectively. The following extract emphasises the importance of the Road Note: “Surface dressing can be used successfully on all types of roads, from the country lane that carries only an occasional vehicle to trunk roads and motorways carrying thousands of vehicles a day. It provides a simple but cost-effective form of maintenance that can play an important part in a highway infrastructure asset management plan. Surface dressing has inherent advantages over other options for road surface renewal: its conservative use of material over thicker asphalt overlays and the avoidance of the need to take up, and subsequently process, existing pavement layers. Used appropriately surface dressing can be an important contributor to minimising the whole life cost of road pavements. Surface dressing can also help with network resilience by being designed correctly for full temperature regime and by acting as the surfacing layer to prevent water penetration and help avoid damage caused by cold weather, ice and snow”.
The attention paid to design, correct installation, supervision and aftercare is probably more important with surface dressing than with more expensive forms of construction. Lack of attention to detail may reduce the service life of a surface dressing; the benefits of adequate control, particularly in the period when traffic is first allowed on the new surface dressing, cannot be over emphasised.
The principal differences from the Sixth edition are: Key concepts and technical terms are briefly defined in RN 39 with external references supplied as a guide for more information i.e. RSTA ADEPT Code of Practice for Surface Dressing; Updated references to guidance documents such as the MCHW & RSTA / ADEPT Code of Practice included throughout; Updated Map of the UK Surface Temperature Categories to reflect the latest information provided by the UK MET office; New recommended PSV levels for less heavily trafficked roads. The surface dressing types presented in RN 39 are coded for convenience; The recommended season has been slightly reduced for 10&6 Racked In Surface Dressing. Tables 9.2.6a and 9.2.6b have been combined into one table showing secondary factors affecting the design. The date of publication for all references, except the House of Commons documents, have been removed to reduce continuous revisions of the Road Note 39 to reflect updated reference materials such as British Standards and guidance documents such as the MCHW and RTSA / ADEPT Code of Practice. There are three new design examples in Appendix A and a new Appendix B – Example Check Table for Rate of Spread, Type and PSV for sites F, G and H.

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