A vehicle configured to be moved along a rail includes rollers which in use engage the rail such that each roller has a contact area with which the roller is in contact with the rail. The contact areas of the rollers are positioned to define a beam with a longitudinal beam axis, a rectangular form in a cross section perpendicular to the longitudinal beam axis and a first beam side, a second beam side, a third beam side and a fourth beam side, in which the first and third beam side extend perpendicular to the second and fourth beam side, at least two rollers define the first beam side, two rollers define the second beam side, one roller defines the third beam side, and one roller defines the fourth beam side. An assembly includes the vehicle and a rail.