Introduction
Subway operators have complained about discomfort caused
by whole-body vibration. To address this issue, an extensive
study on vibration exposure of Montréal subway operators
has been previously realized, where the vibration levels were
measured on the different subway lines and for different type
of motor cars1). Depending of the motor car type (MR-63
and MR-73), the average A(8) values were between 0.39 and
0.58 m/s2 weighted2), for an average daily exposure of 5.3
hours. The problem involves mainly the MR-73 motor cars,
as the MR-63 motor cars should be replaced in the following
years. This MR-73 motor car is mounted on rubber tires, and
another study has shown that the running rack (supporting the
tires) were very flat (International Roughness Index in average
lower than 1.5 m/km)3). Thus, the source of vibration
appeared to be mainly from internal dynamic of the motor
car, excited by out of balance masses located in the subway
wheels and tires1). In addition, the operator current seat is
amplifying the vertical vibration, with a SEAT value of 1.05.
Thus, the study recommended the use of a suspension seat
to reduce the vibration exposure of subway operators. The
recommended dynamic characteristics for the suspension seat
were a natural frequency smaller than 1.7 Hz and a damping
ratio of about 0.45, in order to attenuate the 2.4 Hz dominant
frequency of the MR-73 motor car1).