Internationally, km/h is the most commonly used unit of speed on traffic signs and road vehicle speedometers. The SI representations, classified as symbols, are "km/h", "km h-1" and "km·h-1". Several other representations of "kilometres per hour" have been used since the term was introduced and many are still in use today; for example, dictionaries list "km/h", "kmph" and "km/hr" as English abbreviations.