History Weren't 4 headlights a federal mandate in 58?

I'd have to say that oldiron 440 gave the correct answer, Feds didn't "mandate" 4 headlights, They finally allowed the 5-1/2 inch lights if you had four head lights.

In many states you can't run single 5-1/2 inch headlights legally per state vehicle codes. Back in the 70's when running small headlights on rods was a fad guys were getting tickets for the single 5-1/2 inch lights in some places.

 

The original 1940 'mandate' for 7" sealed beams wasn't done at a federal level. This came about by a group of mostly rural midwest states getting together (with others following later) making them a state requirement. Owners failing to repair/replace broken lenses and tarnished reflectors had become a real safety issue with night-time accident rates rising because of this. This led to further requirements in some states of replacing pre-1940 light assemblies with the now-standard sealed beam 7" lights, which is why those 'conversion' kits that show up once in a while on/for earlier cars came into existence.

The 1958 'legalization' of four headlights was actually an anomaly; up until then, headlight regulation was done at the state level. Detroit realized that trying to address this at the state level would be time-consuming and needed quicker action, so appealing to the feds short-circuited this. The Feds didn't actually have any specific standards other than the requirement that they be 'sealed beam' construction (following the states lead) until 1968 when the National Highway Traffic Safety Administration was formed, at which point they took over from the states. This only applied to manufacturers though, the states were still charged with enforcement as per their local laws.

Four headlight systems are superior to two light systems. The compromises needed to put both low and high beams in one lamp assembly degrades high beam performance. With speeds climbing due to the construction of the Interstate Highway system in the '50s, lighting that could project further was needed.

 

Crazy has it. Chrysler had to jump fast because they going on 57 Chrysler’s until someone found they were not legal in many states seeing a 57 with the single where two were designed always looked weird to me.