Here is a rugged, autonomous robotic platform from NEX Robotics that can carry a considerable amount of load around and even tow a car. The 0x-ALPHA vehicle has an on-board computer with up to an Intel Core i7 processor, differential drive with continuous track, a camera, and 2-hours of battery life.
The machine has a ground clearance of 88mm. It is powerful enough to tow a car and even carry a human. Like what you see? You can find out more about the robot here.