A
speedometer or a speed meter is a
gauge that measures and displays the instantaneous
speed of a vehicle. Now universally fitted to
motor vehicles, they started to be available as options in the 1900s, and as standard equipment from about 1910 onwards. Speedometers for other vehicles have specific names and use other means of sensing speed. For a boat, this is a
pit log. For an aircraft, this is an
airspeed indicator.