Heavy/Falling Weight Deflectometer (HWD/FWD)
FWD testing is a critical tool in the evaluation of existing pavement condition. This testing simulates truck/aircraft loadings and measures the pavement response to such loadings in terms of deflection. Analysis of FWD data allows for backcalculation of the modulus of the various pavement layers (and the effective structural number of flexible pavements), including the degree of slab support (modulus of subgrade reaction, k) in composite and rigid pavements, as well as evaluation of the performance of transverse cracks/joints in terms of load transfer efficiency (LTE) and voids for composite and rigid pavements. This information is used to determine those pavement layers (including subgrade) that are weak, and hence evaluate the likely causes of pavement distresses. The FWD data can also be incorporated into an analytical (mechanistic) pavement design approach for assessment of remedial measures.