Horizontal directional drilling machines (HDD) are steerable, trenchless drilling rigs for the installation of pipes, conduits, and cables underground in a shallow arc. They are commonly used to install pipes, conduits, and cables below waterways and existing roadways without disturbing the ground above. HDDs are typically heavy-duty vehicles fitted with track drives, operator controls, and drilling machinery.
An HDD in the field. Image credit: DitchWitch