In automotive lighting, external lighting functions in particular are subject to international rules. It is essential that lighting functions should have been designed in compliance with essential mechanical, optical, geometric and structural criteria so that the same could be used on the vehicle. In this study, fog lamps, which are used to improve lighting especially in cases of fog, snowfall, heavy rain conditions are discussed for the safety of driver and the passengers. With fog lamps in recent years, cornering function has also been combined in the same equipment. In the current study, geometrical parameters were got for the suitability of fog lamp and cornering lamp on the vehicle. Thus, a method was obtained in order to reveal a product in compliance with legal requirements just in the beginning of design development phase of all vehicles. Thanks to this method, contribution was made to the design of other parts around the fog lamp so that the same will not affect the vision for illumination.