The light-guiding optical system comprises at least one light guide (1) made from an optically transparent material with an associated collimating element (2), and a light unit (3) to emit light rays (10) into the collimating element (2). The light guide (1) comprises on its front side an output surface (12) for the output of light rays (10) conducted by the light guide (1) out of the light guide (1), and on its bottom or top side, a binding surface (11) to bind light rays (10) collimated by the collimating element (2) into the light guide (1). The light guide (1) further comprises at least one reflective means (4) to produce light patterns (A, B, C) on the output surface (12) that comprises surfaces (41, 42, 43) configured for total reflection of at least a part of the light rays (10) falling onto them, a part of the light rays (10) reflected this way being directed by the reflective means (4) towards the lateral surfaces (15) and the remaining part being directed straight to the output surface (12) of the light guide (1). The reflective means (4) of the light guide (1) comprises two lateral reflective surfaces (41, 43) opening from a common contact edge (44) and configured for total reflection of the incident light rays towards the lateral surfaces (15), and one central surface (42) comprising one or more central reflective surfaces (42′), the central surface (42) touching each of the lateral reflective surfaces (41, 43) at one point at the most.