Horses had replaced oxen on farms by 1900. Almost bulk of the field labor was done using horses. Because oxen were too sluggish to operate these devices efficiently, horses were utilized for draft power. Also, a horse is much easier to care for than an ox. The need for a more efficient way to work fields led to the development of the tractor. These machines combine the power and traction of a motor vehicle with that of a plow or harvester. They usually have a shovel or other similar device attached to the end of a long arm that is controlled by the driver from a seat inside the cab. Tractors are useful in fields that are too small for a full-size car, such as gardens, lawns, and small crops. They can also be used as a mode of transportation, although they are most commonly seen working in fields. Horses continued to be used beyond the time when most farmers switched to tractors because some farmers liked the look of horses and knew they could get more work out of them if they kept them as helpers rather than replacements. Horses also require less space than tractors and don't need to be stored outside during bad weather. Finally, a tractor will not break down every time it needs to be repaired which means it cannot be used at a moment's notice like a horse.