We introduce an automotive vehicles taillights module, which consists of a wedge light guide bar, lens, and light emitted diode (LED). The LED light is focusing coupled to the edge of the light guide bar by a lens. The wedge light guide bar is designed with a prism structure at the bottom to ensure light rays come out from the top face. The overall light utilization efficiency is improved by the combination of a small divergence light source and a wedge light guide bar. This taillights module is designed by a 3D graphics software Solidworks and analyzed by the ray tracing method. We propose an efficient algorithm to increase the lighting uniformity by modifying the prism structure. The overall light utilization efficiency is 82.16% and the lighting uniformity is substantially increased to 93.45%.