Drivers who travel between the United States and Canada or plan on renting a car for an international business trip or vacation should understand that driving rules vary from country to country. One noticeable difference is the side of the road vehicles travel on, as well as the measurement system used for calculating speed and distance. Although speedometers will often feature both mph (miles per hour) and kmh (kilometers per hour), it helps to have a rough idea of the conversion between the two speed measurements. Every mile per hour in speed translates to roughly 1.7 kilometers per hour. Therefore, if the posted speed limit is 55 mph in the United States, expect to travel at 88.5 kph in Canada. Always heed speed limit postings and regularly check your vehicle's speedometer to ensure you are driving at or below the legal limit. Traffic offenses that might be tolerated in one country may not be tolerated across the border, so always obey the local laws when behind the wheel.