The impact load caused to a medium by drop of a hammer, results in propagation of stress waves comprising of body waves and surface waves. Surface waves are chosen for the diagnostic investigation of pavements in view of its advantages over the body waves. Since the energy share of the Rayleigh waves is two thirds of the input energy and also they are subjected to less dispersion and attenuation losses.

The experimental set up consists of source equipment i. e., Light Weight Hammer Drop Tester (LWHDT), Vibration Meter, Digital Storage Oscilloscope (DSO) and Mass Storage Unit (MSU) Propagated wave forms are stored in computer diskettes and later analysed to derive the parameters like wave velocity, attenuation coefficient and later to determine the dynamic modulus of elasticity and other material parameters to investigate the structural strength of pavement layers.

The equipment developed was used in testing the newly constructed flexible pavement layer viz., subgrade, sub-base, base and surface courses. Different nomographs were developed in determining the dynamic modulus of elasticity of a pavement layers with the input parameters like hammer weight, height of drop, impulsive force and wave velocity.

The main emphasis of this equipment is its cost effectiveness and easiness in the operation compared to impact load equipment like Falling Weight Deflectometer (FWD), Road Rater, Dynaflect etc. Statistical regression models were developed for different pavement layers relating the dynamic modulus of elasticity and the impulse force.