Thursday 4th July 1935
The British Ministry of Transport announced that dipped car headlights would become compulsory. The earliest headlamps were fueled by acetylene or oil, and were introduced in the late 1880s. Acetylene lamps were popular because the flame is resistant to wind and rain. The first electric headlamps were introduced in 1898 on the Columbia Electric Car from the Electric Vehicle Company of Hartford, Connecticut, and were optional. Two factors limited the widespread use of electric headlamps: the short life of filaments in the harsh automotive environment, and the difficulty of producing dynamos small enough, yet powerful enough to produce sufficient current. “Prest-O-Lite” acetylene lights were offered by a number of manufacturers as standard equipment for 1904, and Peerless made electric headlamps standard in 1908. Pockley Automobile Electric Lighting Syndicate based in the UK marketed the world’s first electric car lights as a complete set in 1908, which consisted of headlamps, sidelamps and tail lights and were powered by an eight-volt battery. In 1912, Cadillac integrated their vehicle’s Delco electrical ignition and lighting system, creating the modern vehicle electrical system. “Dipping” (low beam) headlamps were introduced in 1915 by the Guide Lamp Company, but the 1917 Cadillac system allowed the light to be dipped with a lever inside the car rather than requiring the driver to stop and get out. The 1924 Bilux bulb was the first modern unit, having the light for both low (dipped) and high (main) beams of a headlamp emitting from a single bulb. A similar design was introduced in 1925 by Guide Lamp called the “Duplo”. In 1927, the foot-operated dimmer switch or dip switch was introduced and became standard for much of the century. 1933–34 Packards were equipped with tri-beam headlamps, the bulbs having three filaments. From highest to lowest, the beams were called “country passing”, “country driving” and “city driving”. The 1934 Nash also used a three-beam system, although in this case, the bulbs were conventional two-filament type, and the intermediate beam combined low beam on the driver’s side with high beam on the passenger’s side, so as to maximise the view of the roadside while minimizing glare toward oncoming traffic. The last vehicle with a foot-operated dimmer switch were the 1991 Ford F-Series and E-Series [Econoline] vans. Fog lamps were new for 1938 Cadillacs, and their 1954 “Autronic Eye” system automated the selection of high and low beams. Directional lighting was introduced in the rare, one-year-only 1935 Tatra 77a, and later popularised by the Citroen DS. This made it possible to turn the light in the direction of travel when the steering wheel was turned, and is now widely adopted technology. The standardised 7-inch (178 mm) round sealed beam headlamp was introduced in 1940, and was soon required (exactly two per car) for all vehicles sold in the United States, freezing usable lighting technology in place until the 1970s, for Americans. Because the law was written to prevent ‘bad headlights,’ it by design looks backwards and has historically not been able to deal with improved, innovative designs. In 1957, the law changed slightly, permitting Americans to possess vehicles with four 5.75-inch (146 mm) round sealed beam headlamps, and in 1974, these lights were permitted to be rectangular as well. Clear aerodynamic headlight covers were illegal in the U.S. until 1983, so a work-around was used for the U.S. market, the pop-up headlight. Britain, Australia, and some other Commonwealth countries, as well as Japan and Sweden, also made extensive use of 7-inch sealed beams, though they were not mandated as they were in the United States. This headlamp format was not widely accepted in continental Europe, which found replaceable bulbs and variations in the size and shape of headlamps useful in car design. This led to different front-end designs for each side of the Atlantic for decades. Technology moved forward in the rest of the world. The first halogen lamp for vehicle headlamp use, the H1, was introduced in 1962 by a European consortium of bulb and headlamp makers. Shortly thereafter, headlamps using the new light source were introduced in Europe. These were effectively prohibited in the US, where standard-size sealed beam headlamps were mandatory and intensity regulations were low. US lawmakers faced pressure to act, both due to lighting effectiveness and vehicle aerodynamics/fuel savings. High beam peak intensity, capped at 140,000 candela per side of the car in Europe, was limited in the United States to 37,500 candela on each side of the car until 1978, when the limit was raised to 75,000. An increase in high beam intensity to take advantage of the higher allowance could not be achieved without a move to halogen technology,and so sealed beam headlamps with internal halogen burners became available for use on 1979 models in the United States. Halogen sealed beams now dominate the sealed beam market, which has declined steeply since replaceable-bulb headlamps were permitted in 1983. High-intensity discharge (HID) systems were introduced in the early 1990s, first in the BMW 7-series. European and Japanese markets began to prefer HID headlamps, with as much as 50% market share in those markets, but they found slow adoption in North America. 1996’s Lincoln Mark VIII was an early American effort at HIDs, and was the only car with DC HIDs. Since U.S. headlight regulations continue to be different from the ECE regulations in effect in the rest of the world, the disputes over technological innovation continue today, including over automatic dimming technology.