A falling weight deflectometer (FWD) is a testing device used by civil engineers to evaluate the physical properties (strength) of pavement. FWD data is primarily used to estimate pavement structural capacity for overlay design and to determine if a pavement is being overloaded. Use includes highways, local roads, airport pavements, harbor areas and railway tracks. The machine is usually contained within a trailer that can be towed to a location by another vehicle. It can also be built on a pickup truck, inside a mini van or on a heavy truck with measuring system.
A Light Weight Deflectometer (LWD) is a portable falling weight deflectometer. A Heavy Weight Deflectometer (HWD) is a falling weight deflectometer that uses higher loads, used primarily for testing airport pavements.