It seems that building a fully automated land vehicle is a lot harder than doing the same thing for air or water craft. In the sky, guided missiles and remotely piloted aircraft are becoming very sophisticated, being capable of running for days and ranging thousands of miles. Indeed, a team of amateurs recently flew a aircraft across the Atlantic Ocean, navigating by GPS and monitored via satcom telephone. The USAF's RQ-4 Global Hawks routinely fly for days at a time. Unmanned remote Underwater vehicles and drone boats are becoming more common.

However, the results of a recent DARPA competition to develop an unmanned robotic land vehicle showed that engineers have a long way to go before they can build a robotic vehicle that can handle the challenges of overland travel. The goal was 150 miles, but the farthest any of the 16 competitors got was 7.4 miles before they got stuck or ran so far off the course that it couldn't get back.

The biggest problem is the sensors, data processing and AI needed to handle the myriad different types of terrain found going overland is beyond the level of current technology. That, said, they will come eventually

Robotic Combat Vehicles Just Want to Talk