The light-conductive optical system comprises a planarly shaped light guide (1) made from an optically transparent material with an associated light unit (3) and a collimating element (2). The light guide (1) comprises an output surface (12) for the output of light rays (10) and a binding surface (11) to bind light rays (10) to the light guide (1). The output surface (12) and the binding surface (11) are situated on surfaces that transversally connect the top (5) and bottom surface (6) of the light guide (1) and the binding surface (11) comprises a partial surface (11c) situated opposite the output surface (22) of the collimating element (2) and a lateral partial surface (11a, 11b) at one or both sides of the partial surface (11c). The height (v) of the output surface (22) is bigger than the thickness (t) of the light guide (1) so the output surface (22) reaches above the top surface (5) and/or below the bottom surface (6) of the light guide (1) with its overlapping part (8, 9). The light guide (1) is, for each overlapping part (8, 9), fitted with at least a pair of reflective means (4a, 4b; 4c) comprising the first reflective means (4a, 4b) situated opposite the overlapping part (8, 9) to bind at least a part of light rays (10) exiting from the overlapping part (8, 9) and to reflect them to the second reflective means (4c) adapted to direct light rays (10) against the lateral partial surface (11a, 11b).