[dieseljeep]

Originally Posted by MadMan

The requirement for sealed beams dates back to the early days of electric light. Cars (if you were lucky enough to have that new-fangled electricity on your car!) used to have a small light bulb inside a big lens housing, just like today. But because of light bulb technology being rather poor back then, the filament burning off would blacken the inside of the glass bulb and it would make very little light, which would be very dangerous to drive at night. Especially since halogen lights were not a 'thing' yet. So for safety's sake, the government said you need to use sealed beam lamps, because the filament is in such a large space, that when it blackens the glass, it would only be a small part, and would still emit enough light to be safe.

Of course, light bulb tech was probably good enough by the 50s or 60s to not warrant this anymore, but it's just one of those laws that stayed on the books for too long a time. By the late 80s, the regulations were changed. Some new trucks still use sealed beams, probably just because they're easier to manufacture - and the carmaker does not need to have a headlight design approved by the Department of Traffic (DOT).

My 2006 Jeep Wrangler still uses the large round headlights like were used in the '50's when the car manufacturers went to 12 volt. I guess they wanted the authenticity of the earlier models. Some of the 80's models, they went with the rectangular type that some of the others used. much to the dismay of the Jeep purists.