A lighting device for vehicles, having a flat light guide containing - two opposing flat sides, - one light input coupling surface for the entry of light at a light input coupling side of the flat light guide, - one light output coupling surface for emitting the light entering at the light input coupling surface, wherein the light output coupling surface is located at a light output coupling side of the flat light guide in order to generate a specified light distribution, - one narrow lateral surface (10, 10', 10"), connecting the flat sides with each other and extending from one lateral border of the light output coupling side, - one collection surface adjacent to the light input coupling surface, shaped in such a manner that a partial light beam of the entering light striking the collection surface is reflected in total towards the light output coupling surface without the partial light beam striking the narrow lateral surface (10, 10', 10"), wherein - the light output coupling surface features a number of protrusions and depressions alternately arranged in transverse to the main beam direction, with the protrusions featuring at least two lateral slopes tapered at an acute angle (α) and one tip surface; - the depressions are formed by a bottom area from which the lateral slopes of the neighbouring protrusions rise; characterized in that, - the tip surface is shaped in such a manner that a partial light beam which is totally reflected from the collection surface and/or the flat sides and an additional partial light beam originating directly from the light input coupling surface are refracted at the tip surface to generate a central region of light distribution; - the lateral slope of the protrusion is shaped in such a manner that another partial light beam (20, 21) of the input light striking the lateral slope is totally reflected towards the tip surface and exits the flat light guide at the tip surface to generate a lateral region (L2, L3) of light distribution; - two opposing flat sides, - one light input coupling surface for the entry of light at a light input coupling side of the flat light guide, - one light output coupling surface for emitting the light entering at the light input coupling surface, wherein the light output coupling surface is located at a light output coupling side of the flat light guide in order to generate a specified light distribution, - one narrow lateral surface (10, 10', 10"), connecting the flat sides with each other and extending from one lateral border of the light output coupling side, - one collection surface adjacent to the light input coupling surface, shaped in such a manner that a partial light beam of the entering light striking the collection surface is reflected in total towards the light output coupling surface without the partial light beam striking the narrow lateral surface (10, 10', 10"), - the light output coupling surface features a number of protrusions and depressions alternately arranged in transverse to the main beam direction, with the protrusions featuring at least two lateral slopes tapered at an acute angle (α) and one tip surface; - the depressions are formed by a bottom area from which the lateral slopes of the neighbouring protrusions rise; - the tip surface is shaped in such a manner that a partial light beam which is totally reflected from the collection surface and/or the flat sides and an additional partial light beam originating directly from the light input coupling surface are refracted at the tip surface to generate a central region of light distribution; - the lateral slope of the protrusion is shaped in such a manner that another partial light beam (20, 21) of the input light striking the lateral slope is totally reflected towards the tip surface and exits the flat light guide at the tip surface to generate a lateral region (L2, L3) of light distribution;