Back in the 1980s headlight companies developed sealed reflector/lens assemblies that permitted replacement of the bulb. This was a breakthrough: Not only were the replaceable-bulb halogens brighter than the older style of light, but they also meant that burning out a bulb didn't have to mean replacing an entire assembly.
There was just one problem: Federal rules demanded "sealed beams" or all-in-one headlight assemblies with a nonreplaceable bulb inside. It took until 1984 for American drivers to get the better headlights they wanted while regulators got a grip on the notion that the bulbs should be replaceable.
It should come as no surprise that technology is transforming cars much faster than stodgy government rules can adjust. More recently, laws specified the wattage of bulbs for taillights and other lights. LEDs use much less power than incandescents and didn't meet that requirement even though they were as bright or brighter than the old filament-based bulbs, so those regulations had to change.
As the pace of innovation accelerates, the gap between invention and regulation widens, making it unclear whether some of the coolest new automotive tech will actually be allowed in American cars. These clever car systems, unfortunately, are having a hard time getting approval in the U.S.
Now pay attention to this one. John's 3rd brake light flashing? OH OH!!
Strobe Brake Lights
Mercedes-Benz sells cars in Europe that are equipped with brake lights that flash quickly in response to hard brake pressure. The idea is to warn following drivers of a sudden stop from cars ahead. But U.S. government regulators say brake lights are allowed to do only one thing: glow more brightly than the taillights. Flashing is off-limits. Mercedes did get approval to install the feature on a few cars, as a trial program, but that's all.