The ADR has been amended to allow convex or flat mirrors, as is allowed in the relevant UNECE regulation, for internal and driver's side external rear vision mirrors; previously the ADR only permitted flat mirrors for these applications.
While flat mirrors provide an undistorted view, enabling detection and accurate judgement of distances of objects in the field of view, convex mirrors can provide a wider field of view and reveal objects that would otherwise be in the blind spot and undetectable by flat mirrors.