The transient deflection of road pavements under the passage of a heavy wheel-load has been related, by studies on experimental and normal in-service roads, to the long- term performance of the pavements. This provides the engineer with a relatively simple method of forecasting the performance and future structural maintenance requirements for existing roads. This report, which does not discuss the research background to the work, is intended to present to the engineer the information he requires to make and interpret deflection measurements. The use of the deflection beam is described in detail, together with the procedure for correcting measured deflections to a standard temperature of 20 degrees c. as an alternative and more rapid means of measuring deflection, the deflectograph and its method of operation are described. Curves to correlate deflection derived from the two methods are provided. Deflection criterion curves, which take into account the changes in deflection which occur with age, are presented and used to estimate the life expectancy of pavements being considered for structural maintenance. Finally curves are provided from which the reduction in deflection and extension of life likely to accrue from the use of different thicknesses of rolled asphalt overlay can be deduced. Examples illustrate the use of the deflection method in forecasting life and in the preparation of maintenance schedules.

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