Abstract: A vehicle for traversing a surface such as for carrying out an inspection, survey or maintenance operation upon that surface comprises two bodies interconnected by means to move the bodies towards and away from each other, each of those bodies being supported upon a multiplicity of resilient bristles (13; 25; 32) extending from it, the bristles of each body being mounted in groups upon bristle-carrying members (10; 23; 31) each guided for movement towards and away from the body, and fluid pressure means (25; 22; 34) to effect the guided movement of the bristle-carrying members in at least one of those directions.