A speedometer is an instrument found in vehicles that measures and displays the speed at which the vehicle is traveling. It typically shows speed in miles per hour (mph) or kilometers per hour (km/h) on a dial or digital screen. Speedometers help drivers maintain safe speeds and comply with traffic laws. Most speedometers work using a sensor that detects the rotation of the vehicle's wheels. This information is then converted into a speed reading. Some modern vehicles also feature digital speedometers, which provide additional information, such as average speed and trip distance, enhancing the driving experience.