What vehicle type is characterized by being capable of being ridden solely using human power?

The vehicle type characterized by being capable of being ridden solely using human power is the bicycle. Bicycles are designed specifically to be operated by human effort, utilizing pedals which the rider must turn to propel the vehicle forward. This distinguishes them from other vehicle types that require a motor or engine for operation.

In contrast, farm tractors, passenger cars, and motor vehicles operate through powered engines, either fueled by gasoline, diesel, or electricity. These vehicles rely entirely on mechanical power rather than human strength, which is why they do not fit the criteria of being ridden solely using human power.