A common metric unit of speed or velocity. 1 km/h is equal to 5/18 meter per second, 0.621 371 19 miles per hour or 0.911 344 42 feet per second. The only correct symbol for this unit is km/h; variations such as kmph or kph should not be used
Russ Rowlett (Director), How Many? A Dictionary of Units of Measurement, Center for Mathematics and Science Education University of North Carolina, USA 2005. http://www.unc.edu/~rowlett/units/dictA.html, (Unit of Meas and Covr Factors - Amer) {608}