A bicycle or motorcycle propelled solely by its two wheels embodies a fundamental form of transportation. A common example is a standard bicycle driven by pedals connected to a chain that rotates the rear wheel. This configuration provides a direct link between human effort and vehicular motion.
This simple yet effective mechanism offers numerous advantages, including efficiency, maneuverability, and a low environmental footprint. Historically, these vehicles have played crucial roles in personal mobility, offering a readily accessible and affordable means of transport. Their evolution has seen continuous refinement in design and materials, leading to increased performance and comfort.