Original sentence: Each headlight had dual filaments, so that a single bulb could provide both high- and low-beam light.For 1978, a rectangular version of the two-lamp system became legal; these measured  wide and  tall.From the 1975 model year, a rectangular version of the four-lamp system was legalized.In 1957, a system of four sealed-beam headlights – two per side, each measuring , was allowed in some U.The following year in 1958, all states allowed the new system.The new lamps were  wide and  tall.Two of the lamps contained two filaments and served as low and high beam, while the other two lamps contained only one filament and were active only during high-beam operation.With only two round sizes and two rectangular sizes allowed, the sealed-beam headlamp mandate greatly restricted styling possibilities for automobiles.cars in 1979, to enable greater high-beam intensity newly permitted by Federal Motor Vehicle Safety Standard 108 without unreasonably high lamp wattage
Edited sentence: American designed vehicles.Each headlight had dual filaments, so that a single bulb could provide both high and low-beam light.From the 1975 model year, a new system of four-lamp rectangular sealed-beams began to be used on many U.In 1957, U.Replaceable-bulb headlamps provided the required regulated light distributions, while allowing greater engineering and design freedom.The limited range of standardized, authorized sealed-beam headlight sizes and designs greatly restricted styling possibilities for automobiles.This generally influenced the styling / design of U.Two served as low and high beam, like the  version, while the remaining two were additional "high-beam" only lamps.cars in 1978, to enable halogen technology under Federal Motor Vehicle Safety Standard 108, which at the time required all headlamps to be of sealed-beam construction.legislation changed, to allow four sealed-beam headlights – two per side, each measuring.marketed automobiles, joined three years later by a two-headlamp system