Car speedometers also tend to read fast [possibly for safety]. By spec, I believe that they are allowed to read 10% faster than actual speed but more severely p

Car speedometers also tend to read fast [possibly for safety]. By spec, I believe that they are allowed to read 10% faster than actual speed but more severely penalized if the read slow. Best / Quickest source : http://www.popularmechanics.com/cars/how-to/a3127/4260708/ http://www.popularmechanics.com/cars/how-to/a3127/4260708/