Turquoise taillights tell you this Mercedes is driving autonomously

Authorities in California and Nevada have both granted Mercedes-Benz permission to test out a new car-to-human communication idea. While we're still some way away from road cars emoting like some of the concepts we've seen in the past few years, the automaker will use turquoise-colored marker lights to indicate when its advanced partially automated driver assistance feature is operating so other road users are aware.

Mercedes' Drive Pilot system is what's known as Level 3, or conditionally automated driver assist, according to the SAE International's classification system. In some ways, it's similar to so-called Level 2+ systems like General Motors' Super Cruise or Ford's BlueCruise in that it has a tightly controlled operational design domain that only allows it to operate on pre-mapped restricted-access highways.

But unlike those systems, Drive Pilot lets you take your hands and eyes off the road. That's because it will only work at speeds of up to 40 mph (65 km/h)—it's not meant for cruising at speed. The lower speed envelope means there's enough time for Drive Pilot to warn the human behind the wheel that it's time to think about driving and take over.