The word “dual” has always inspired car fans. Dual carburetors once promised a boost in performance, sometimes enhanced by dual camshafts. Dual exhausts are back in fashion, only from a design point of view though. Is it the same for dual headlights?
Yes and no. Dual headlights are an invention of the 1960s in Europe. For single headlights with combined dipped and high beam only one single light source used to be available in Europe. It was the R2 two-filament lamp, also known as the Osram Bilux®. But then halogen lamps have been around since 1961, although they only had one filament, which means they could only provide either dipped or high beam. This led to the idea of using a separate headlight for each function. Dual headlights were born.
While halogen lamps in the form of the H4 lamp have been around since 1974, offering dipped and high beam from one single headlight, dual halogen headlights are still a sensible solution. The lamp types used, such as the H1 and H7, are superior to the H4 lamp, and the headlights can be optimized for the particular light. The headlights just shouldn’t be too small. There are cases where a really big single headlight with H4 is superior to its little dual brothers – at least as far as dipped beam is concerned.
When xenon technology first found its way into cars, dual headlights were in fashion again. During the first few years, the new light was only available in dipped beam headlights. The much more rarely used high beam continued to come from a separate halogen headlight. Then bi-xenon lit up the darkness and dual headlights actually became superfluous. Now dipped and high beam came from one headlight, and it would have been good for it to get the entire available space at the front of the vehicle. Size also matters when it comes to xenon. Designers fought tooth and nail (or perhaps drawing board and pencil) against the abolition of dual headlights. So bi-xenon also often got additional high beam headlights. They were only used for headlamp flashers though. Even though there was a compelling technical reason for this – igniting xenon lamps only for headlamp flashers creates no excessive wear – the main reason was very clearly the design.
That’s exactly how it is with the latest lighting technology, LEDs. Here, all the lighting functions are possible from one single headlight, and that’s indeed sensible from a technical point of view. However, designers at some manufacturers stick tenaciously to the design options offered by dual headlights. And concepts such as the “four-eyed face” also still play a major role. Even though the technology is actually outdated.
What Jens says about the topic you can read here