What self-propelled device did Leonardo da Vinci design as an early mechanical vehicle?

Leonardo da Vinci designed a self-propelled cart as an early mechanical vehicle.

The cart appears in drawings made around 1478–1480. It used coiled springs to store energy, while a system of gears controlled the release of that energy to the wheels. Steering could be set in advance, allowing the cart to follow a predetermined path rather than being driven by a person sitting inside it.

The device is sometimes described as a robot or as an ancestor of the automobile, but those labels need qualification. It was not an engine-powered car, and its route was limited by its mechanical programming. The design was reconstructed in the twentieth century, and working replicas demonstrated that its basic mechanism could operate. Its importance lies in combining stored mechanical energy, gearing, and programmable motion several centuries before powered vehicles and automated machines became widespread.