A page describing an odometer, from the Theatri Machinarum Supplementum by Jacob Leupold, 1739. An odometer or odograph is an instrument that indicates distance traveled by a vehicle, such as a bicycle or automobile. The device may be electronic, mechanical, or a combination of the two. In countries where Imperial units or US customary units are used, it is sometimes called a mileometer or milometer, or, colloquially, a tripometer.