Gas-driven post hole diggers exist that are operated by one or two people. No slip grips are standard. High-quality gas powered augers such as the Stihl BT 130 auger, have safety bars that stop the auger if a major obstruction is hit.
Augers have a motor that can vary in size. Some augers come with bits already, while others have bits that must be purchased separately. Bit sizes are usually 4 inches to 10 inches in diameter, and bit extenders are sometimes available for digging deeper holes. Planting augers have smaller motors and are generally used for planting bulbs and other very small landscape features.