This manual is a step-by-step guide through the relevant stages in the preparation process for applying a two-layer porous asphalt road surface. A checklist with points of attention when laying two-layer porous asphalt (PA) is included as an appendix. This assumes that two-layer porous asphalt has already been chosen and therefore does not deal with the pros and cons of various types of road surfaces. The manual provides insight into the costs and benefits analysis, and the functional and civil engineering aspects of two-layer (PA) road surfaces. To obtain and maintain optimal quality, attention must be devoted to construction, management and maintenance. Risks could be given to the contractor, using alternative contract forms. This may be beneficial for the quality as it gives the contractor extra encouragement to provide good work. This can work as a stimulus particularly in the case of relatively new applications such as toe-layer PA. This manual deals with all aspects. The most common variant of two-layer PA currently employed is used as a basis: a 40-50 mm thick bedding course with a grading of 11 to 16 mm and a carpet of about 25 mm thick with a grading of a 4 to 8 mm.
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