The LWD is a light weight, hand-operated tool used to determine the stiffness of unbound materials by measuring the deflection under a load applied by a falling weight of known mass. Once deflection is measured, an estimate of the modulus value is obtained based on the force required to generate that deflection in the soil type being tested. LWD is advantageous because it provides a more representative picture of a pavement’s load capacity than laboratory density measurements; can verify the soil properties used during pavement design quickly and directly; obtain results more quickly on-site, reducing construction delays, and allowing the inspector to stay on-site because there is no lab work involved.