The long-term performance of a surface dressing trial on A413, Amersham

A length of road with sections each having been surface dressed to a different design, originally laid down as a test site with varying micro-texture and macro-texture, was monitored for changes with time in the properties of the different sections. All dressings have performed well despite non-ideal aggregate sizes and types of surface dressing having been used. The linear rate of decay of macro-texture during the first two years was proportional to the Flakiness Index of the primary aggregate, whilst absolute values of macro-texture cannot be confidently predicted from the data types normally available within current United Kingdom practice. Therefore, macro-texture must be strongly influenced by one or more properties currently unrecognised and further work will be required, and data collected, to develop a method of predicting surface dressing macro-texture performance at the design stage. (A)