Lightpipes are essential to automotive interior illumination systems. These light distribution systems are constrained by geometrical complexity, which makes both analysis and fabrication difficult. Their development depends on empirical procedures that are often inefficient and time-consuming. We review the successful modeling procedure of one complete automotive illumination light-pipe system, which includes a light source and a light pipe. The success of modeling is verified by comparing results to experimental measurement. A simple method of light-pipe evaluation based on nonsequential ray trace optical modeling for the automotive illumination industry is demonstrated. Extensive modeling of the light sources for these systems is also included.