The classic vertical 7-inch round headlamp design is facing extinction, a victim of safety and fuel economy regulations coupled with the march of technology.

The shape effectively became the law of the land in 1940 when a patchwork of state regulations covering automobile illumination began to be harmonized in an effort to improve safety on America's expanding highway network, and to make it easier for budding motorists to find replacements for this very essential piece of equipment no matter where the road took them.

At the time, the lights were all of the sealed-beam type, and technically known as the Par 56 - engineer-speak for parabolic aluminized reflector, 56/8ths of an inch. Patented by General Electric just a year earlier, they incorporated both low and high beams and were better protected from the elements than the variety of replaceable bulb lamps that they replaced.

Stewart Reed, the chair of Transportation Design at the Art Center College of Design in Pasadena, Calif., says cars of the day were literally drawn around them, stylists always searching for creative ways to generate original fender forms that incorporated the standardized circles.

In many respects they also helped cement our enduring relationship with the automobile, the wide-open, exposed eyes anthropomorphizing them into relatable characters. Herbie the Love Bug would not likely have come to life if he were a 1986 Ford Taurus.

In 1957 the rules were updated to allow for two pairs of "6-inch" headlamps (5 ¾-inch, to be exact) that split the work between individual low and high beams. Andrew Smart, director of Industry Relations at the Society of Automotive Engineers, says this provided for the kind of low-profile front end designs stylists craved.

Round headlamps of both types would rule until the 1970s, when rectangular sealed-beam units were cleared for use in the United States, followed by the first modern replaceable bulb headlamps in 1983, which led to the myriad shapes that followed.

Today, only three mass-market vehicles that ape the classic 7-inch upright look remain; each one of them a survivor in its own right.

The Jeep Wrangler, Toyota FJ Cruiser and Mercedes-Benz G-Wagen all sport the familiar face, but with today's technology hidden behind it. Although it is literally the oldest new car you can buy, the Carter-era G-Wagen uses cutting-edge Bi-Xenon bulbs, while the Toyota and Jeep both rely on replaceable halogens. The Wrangler last came from the factory with actual sealed beams in 2006.

According to Reed, the design "is now totally retro. There's no technical reason to do it anymore, it is old technology." He notes that some other throwback automobiles, like the Volkswagen Beetle, present a round graphic when viewed from the front, but in profile reveal designs that are far more complex than their upright forebears. Even the illusory 7-inch fixtures on the Jeep Patriot are slightly canted to the rear.

Unlike the days of forced uniformity, however, Smart says lighting has become as much of a brand identifier and marketing element as anything else on a vehicle, but the proliferation of LED-laden swept-back headlamp clusters isn't all about image. Fuel economy plays a huge role in automotive design today as engineers struggle to improve aerodynamics in the quest for MPG, and the lights are often the tip of the sword in this battle. The "soft" hoods demanded by pedestrian safety standards play a role as well.

This means that only vehicles with intentionally blunt façades, such as serious off-road machines, can still accommodate a couple of personal pan pizza-size light fixtures without much ill-effect. The next "Bugeye" Sprite, on the other hand, will likely have peepers so slim that it will appear to be asleep.