Abstract: Subway operators have complained about discomfort caused by whole-body vibration. To address this problem,
a suspension seat with extensive ergonomic features has been adapted to the confined space of the subway operator
cab. The suspension was modified from an existing suspension in order to reduce the dominant frequency of the subway
vertical vibration (2.4 Hz). The suspension seat has been extensively tested on a vertical hydraulic shaker. These tests
have shown that the SEAT value was lower for a higher vibration level, for higher subject weight, and for the suspension
adjusted at median height. The seat also produces a lower SEAT value when there was a predominance of the 6 Hz
vibration component. The horizontal seat adjustments had no influence on the suspension SEAT value. Removing the
suspension damper also decreases the SEAT value for all the tested configurations. The final version of the suspension
seat prototype was validated during normal subway operation with 19 different operators having weight in the 5th, 50th
and 95th percentile of the operator population. Accelerations were measured with triaxial accelerometers at the seat
cushion, above the suspension and on the floor. In addition to the vibration measurements, each operator was asked
about his perceived discomfort from vibration exposure. Globally, the suspension seat attenuated the vertical vibration
(SEAT values from 0.86 to 0.99), but discomfort due to amplification of the 2.4 Hz component occurred when the suspension
height was adjusted at the minimum, even when the global weighted acceleration was lower (SEAT value < 1).
These results suggest that in order to reduce the discomfort caused by whole-body vibration, the transmissibility of the
seat should also be considered, in particular when there is a dominant frequency in the vibration spectra.