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The introduction of LEDs in automotive lighting has enabled disruptive design changes for a range of functionalities. In particular, signal lighting and day-time running lights can now be realized by visually attractive and brand-specific light-guide solutions. Nevertheless, system efficiency has been identified as a key issue in the implementation of light guide solutions. Light-guide efficiency is influenced by three factors. First, the match between far-field pattern given by regulations and generated one. Second, internal losses inside of the light-guide. Finally, the transfer of LED flux into the light-guide input facet. The latter factor, often denoted as incoupling efficiency, is dominated not only by geometrical light-guide dimensions but also by LED shape and radiation characteristics. In this paper, the influence of LED design on the incoupling efficiency is underlined.