This is the fourth report by Dr. Moss on the investigation of riding comfort at the George Washington University and is a progress report on the measurement of automobile riding-qualities. The previous reports were published in the S.A.E. JOURNAL as follows: September, 1929, p. 298; January, 1930, p. 99; and April, 1930, p. 513. In this report, which was presented at the 1930 Semi-Annual Meeting, the author describes improvements made in two wabblemeters for measuring physiological fatigue caused by riding and the use of two accelerometers to correlate the behavior of the automobile with the physiological results.
Results obtained with two groups of subjects, one consisting of taxicab drivers and the other of university students, are summarized, and the results of preliminary tests of the comparative riding-qualities of different cars as shown by their effects on the subjects are also given.
Two conclusions reached are that the subject's efficiency of performance on the wabblemeter definitely tends to decrease with increase in the length of the driving period, and that a definite, positive correlation seems to exist between the vibrations of the car as recorded on the accelerometer and the amount of fatigue produced as shown by the wabblemeter.