All-terrain power wheelchairs, with their extra large, wide-tread tires, are designed primarily for driving over rough, outdoor surfaces.
Some are equipped with crawler tracks to handle conditions which would be extremely difficult, and potentially hazardous, for a medical power wheelchair. These include:
mud, sand and overgrown grass
rocky roads and paths covered in snow, slush, sleet or ice
steep hills, steep inclines and steep slopes
This may, in part, help to explain why extreme outdoor power chairs appeal to the young and adventurous.