Design guide for road surface dressing (Fifth edition)

Road Note 39 is a guide for the design of surface dressing for roads throughout the United Kingdom. This Fifth Edition of the Report is produced by a Panel representing all sides of the industry, with the Chairman and Secretariat provided by the Infrastructure Division of TRL Limited. The following extract emphasises the importance of the Report and highlights the main differences to previous editions: 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 (Carswell, 1994; Nicholls and Frankland, 1997; Milton et al., 2001). Unfortunately, the attention paid to design, control, supervision and aftercare is frequently less with surface dressing than with more expensive forms of construction. Lack of attention to detail shortens the useful 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 emphasised too strongly. For many years, the design of surface dressing has been carried out according to Road Note 39, which is now in its fifth edition. The principal differences from the fourth edition are: a Incorporation of binder grades and aggregate sizes that have been or are about to be implemented in the UK with harmonisation across Europe. b The appendix on other applications for surface dressing has been extended to include the design of surface dressings for footways, cycleways and untrafficked areas. c A ‘quick guide’ to the design requirements has been incorporated into the Executive Summary. d Reference to tar-bitumen blend binders has been removed. e Details of the necessary preparatory work have been added. f The selection criteria for the type(s) of surface dressing recommended have been revised, removing the need for the ‘total traffic’ parameter. g The recommended aggregate sizes have been reviewed: the 20 mm size has been removed, there is less emphasis on the 14 mm size for single surface dressings, and there is less emphasis on the 10/3 mm size for racked-in and double surface dressings. h The binder spread rates have been reviewed, with specific values added for use with intermediate grade emulsion binders. i The seasons and weather conditions have been revised because the limits vary according to the type of product. j A correction factor for the binder spread rate has been added for late season working. k The division between the south and central regions of the UK has been shifted south. l The necessary timetable of events for surface dressing to ensure good jobs has been emphasised. m Tables and Figures have been renumbered in accordance with the primary section that calls them up so as to provide easier cross-reference. Road Note 39 is a design guide; it is NOT prepared as, nor should it be used as, a specification.