The discrimination of clutch-pedal resistances

A rig was constructed to the approximate dimensions of existing trucks and incorporated a dynamic, spring-loaded, clutch pedal, the resistance of which could be adjusted. Twenty subjects took part in an experiment on the discrimination of pedal resistances. Using the psychophysical method of limits a value of 0·07 was obtained for the Weber Fraction. This figure was reasonably consistent across standard resistances ranging from 89 to 445 N (20–100 lbf) and it may thus be concluded that a difference of at least 7% must exist between foot-pedal resistances for a difference to be detected by 50% of the population.