Sundstrom J., Khan S.

In a combined vibration and passenger survey aboard Swedish Intercity trains a majority of the passengers reported disturbances due to jerks and vibrations. Subsequent lab studies further revealed that the difficulty of reading and writing displayed non-linear frequency characteristics for stationary vibrations in the lateral direction. In the present study a train mock-up was used to investigate how lateral occasional jerks influence passengers' reading and writing. The subjects sat leaned against the seat back with the work material placed in the lap during the exposures. In order to limit the influence of anthropometric differences the 21 subjects were recruited according to pre defined body measures. The study consisted of three parts (A, B, C) whereof the first two were balanced in order. In part A and B the vibration sets comprised of six discrete frequencies (1.25 - 5.0 Hz) with stationary amplitude of 0.3 m/s2. Each frequency was presented with three occasional peak amplitudes (0.7, 1.0, 1.4 m/s2). The transient peaks were one oscillation period long and had a sinusoidal shape. Each peak occured randomly three times over the 25 s long sets. The test subjects gave ratings of experienced difficulty to read and write due to each vibration peak, using Borg's CR-100 scale. In part C, nine amplitude levels (0.43 - 0.7 m/s2) were used for three frequencies (1.25, 2.0, 4.0 Hz). In this part the test subjects were instructed to press a button whenever their reading was disturbed by a peak. The results showed that occasional jerks cause lower levels of difficulty than stationary vibrations of the same acceleration amplitude. However, did only 35% of the jerks at 0.7 m/s2 cause disturbances while reading.