Classicly

While tractors and automobiles are the same in general principles, there is a wide difference between them in design, construction, and handling, due to the differences in the work that they do and in the conditions under which they do it.

An automobile is required to move only itself and the load that it carries. While it can run over rough roads, these must be hard enough to support it; on soft ground it will sink in and be unable to get itself out. It can make great speed over smooth, level roads; but only rarely do road and police conditions permit it to run its fastest for more than a few minutes at a time. For the greater part of its life it develops only a portion of the power of which it is capable.