Maximum speed is the highest speed at which an object can travel. It is usually measured in units of velocity such as kilometers per hour (km/h) or miles per hour (mph). Maximum speed is an important factor in many activities, such as driving, racing, and sports. It is also important in engineering, as it can determine the efficiency of a vehicle or machine. Maximum speed is usually limited by factors such as the power of the engine, the weight of the vehicle, and the friction of the environment.