Mile per hour (mi/h or mph) : A traditional unit of velocity. One mile per hour equals exactly 22/15 feet per second, approximately 1.609 kilometers per hour (km/h), or exactly 0.447 04 meter per second (m/s)
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}