Abstract: A vehicle (1) for travelling along a conduit (2) such as a pipeline having fluid flowing therein is disclosed. The vehicle comprises a first body carrying a first set of retractable bristles (12) for engaging an internal wall of the conduit such that the bristles resist movement of the first body in a first direction more than in a second direction, and a second set of retractable bristles (13) for engaging the internal wall of the conduit such that the bristles resist movement of the first body in the second direction more than in the first direction. A thread follower (16) carries a third set of resilient bristles (18) for engaging the internal wall of the conduit such that the bristles resist movement of the thread follower in the first direction more than in the second direction. A turbine (5) is actuated by fluid flow in the conduit to cause rotation of a reverse traverse screw (14) to move the first body and thread follower towards and away from each other.