The French Drain Harrow uses vibrations to lift and loosen material built up within the stones of a french drain, with the attachment designed in such a way that the Multihog is able to plough through the drain with minimal effort to unblock compacted stones and loosen built up debris from the highway.

This application reduces the costs associated with full scale cleaning or digging operations whilst minimising disruption to the network because the Multihog can work within the hard-shoulder.