On a mid-March afternoon, 3 inches of fresh snow blanketed M-14, a state highway in southeast Michigan. Lane markings were covered in a sheet of white. Ice hung from road signs and cars alike.

These are the conditions that are supposed to scare away self-driving vehicles. Weather is a prime reason so many companies run testing in the sunny confines of places like Arizona and Florida.

But on this day, engineers from Bosch were on the snow-covered road, testing new technology that allows automated vehicles to localize themselves — that is, figure out precisely where they are in the world — primarily via radar.

So far in the self-driving realm, automakers and technology companies have been enamored with other sensors for this purpose. Automated cars are currently using cameras and laser sensors known as lidar.

By comparison, radar, which has been on production vehicles for two decades, has been a staple of driver-assist systems for obstacle detection, and until now, not viewed as a tool for localization. Perhaps it's even underappreciated. Venture capital has flowed into lidar and camera-based solutions for automated vehicles; radar has been viewed as a commodity.

"It's unfortunate that's the perception, but it's probably as it should be," says John Xin, CEO of Lunewave, a startup developing radar-sensing systems. "Over the last 20 years, there's not been a whole lot of game-changing hardware technology coming out of radar sensors."

That's changing. Whether it's global suppliers such as Bosch, or startups such as Lunewave and WaveSense, a recent spinoff from MIT's Lincoln Laboratory, there's fresh innovation being wrung from radar, a technology that first found widespread use during World War II, and was first deployed on production automobiles by supplier Delphi in 1999.

These three companies are rethinking the role of radar in mobility. Here's a rundown of the technology advances underway.