Elon Musk's grand plan of moving beyond passenger cars to truly revolutionize transportation just got a bit grander. In addition to developing an electric 18-wheeler that Tesla plans to unveil next month, Musk wants to make the thing drive itself.

Tesla is working with Nevada authorities to begin testing a robo-rig prototype at some point in the not-too-distant future. “Our primary goal is the ability to operate our prototype test trucks in a continuous manner across the state line and within the States of Nevada and California in a platooning and/or Autonomous mode without having a person in the vehicle," Tesla’s Nasser Zamani told officials with the Nevada Department of Motor Vehicles, according to Reuters.

Assuming Tesla can figure out how to make battery tech work for long-haul trucking (no easy feat), adding autonomy to the equation makes perfect sense. Tesla joins a long list of enterprises working on autonomous long-haul trucking, including Uber, Google spinoff Waymo, Volvo, Daimler, the US Army, and a small horde of startups.

They all see a compelling case for human-free trucking: Big rigs carry 70 percent of all goods shipped across the US, but the industry doesn’t have nearly enough drivers. The American Trucking Associations says the industry needs another 50,000 drivers, and that figure could hit 175,000 by 2024 as more people retire or move on to other careers.

Autonomy also could drive down costs. The American Transportation Research Institute estimates that driver pay and benefits account for nearly 40 percent of a shipping company's costs. And don't forget safety. Big-rig crashes kill 4,000 people on US roads each year and injure another 116,000. Nearly all of them are the result of human error.

Tesla's factory could soon be put to work building an electric, autonomous truck. Tesla

The great news is that the technological challenge of making a truck drive itself on the highway is relatively simple. Compared to navigating city streets swarming with cyclists, pedestrians, and unpredictable motorists, keeping any vehicle within its lane on the open road and maintaining a safe following distance is a breeze. The cost of all those sensors—lidar and top-shelf GPS can run five figures—is a bit easier to swallow in a big rig that costs 120 grand.

But—and there's always a but when you're dealing with leading-edge tech—the technology doesn't really solve the driver shortage problem or truly pay for itself until you kick the human out of the cab entirely. And that is where Musk's plan faces its biggest challenge.