Leonardo da Vinci designed an odometer to record the distance traveled by a cart.
His mechanical odometer counted wheel rotations as the cart moved. A wheel of known circumference advanced a sequence of gears, and the final mechanism displayed the accumulated distance. The design could therefore convert repeated wheel movement into a practical measurement.
An odometer measures distance, not speed. A speedometer shows how fast a vehicle is moving at a given moment, while a tachometer measures rotational speed. Leonardo’s device was especially useful for surveying, mapping, and measuring roads.
The invention illustrates Leonardo’s interest in gear trains and automatic recording. It was not an automobile instrument in the modern sense: the cart had to be pushed or pulled, and the mechanism simply documented its travel. Modern vehicle odometers retain the same basic principle of linking wheel rotation to distance.