Many of the lighting devices on motor vehicles are legally required and arc essential to safe operation on the highway. To maintain performance, it is important that the bulb and sealed unit types employed he readily available, when needed, throughout the country in normal service channels. Therefore, this SAE Standard lists an assortment of current popular types, together with their characteristics, which are recommended for use wherever practicable. It is recognized that because of constantly changing and improving technology, the list may be incomplete. Also, instances may arise in the design of some devices which require the employment of other types while achieving the desired performance.