Development and Evaluation of Bus Seat Dimension to Improve the Fit and Comfort of Malaysian Bus Drivers
3
position of the neck, shoulders, and upper extremities. Therefore, along with the seat itself, the work to be performed must be considered [6], [7].
A body position or posture is considered appropriate if the weight of an individual’s body is transmitted to the seat with the least possible stress on the body
[8]. The weight of the head, the trunk, and the thighs are borne by the headrest, backrest, and seat pan; the weight of the lower legs and feet is transmitted to the
floor, suitable footrest, or in the case of a bus operator’s workstation, the foot pedals.
1.2. MSDs among Malaysian bus drivers
The prevention of musculoskeletal disorders is achieved by interventions, which reduce the probability and severity of injuries. Ergonomic design may reduce
the incidence of compensable back pain by up to one-third [9]. In a study [10] of MSDs among 308 Malaysian bus drivers, the most common
complaint 63.2 was lower back pain while driving, followed by neck pain 54.3, upper back pain 41.8, and shoulder pain 30.7, Figure 1. Elbow pain occurred
least frequently. The bus drivers also attributed their discomfort to the vibration of the vehicle.
Vibration comes most commonly from the steering wheel 43, followed by the seat 31, the gear-shift 15 and the pedal 11, Figure 2. Thus, in designing
the seat, the need to reduce vibration must also be considered.
Figure 1. Frequencies of musculoskeletal complaints of the drivers surveyed
M.Y. Rosnaha et al. AJE Vol.9 2009 1-17
4
43 31
15 11
Percentage of Vibration by Source
Stering Seat
Gear Pedal
Figure 2. Source of vibration
Saporta [2] suggested that to minimize musculoskeletal stresses, the seat should be designed such that:
1 It permits shifting or changing of posture 2 It has a large adjustable back support;
3The seat surface should be accommodating, but not spongy, to accommodate
the forces transmitted to it: and 4 Seat height and angle should be easily adjusted.
All of these features can contribute to good seating posture.
1.3. Anthropometry data and design
Measurement of people’s physical characteristics and abilities anthropometry provides information that is essential to guide appropriate design of occupational
and non-occupational environments, as well as for the design of consumer products, clothing, tools and equipment [11] and to resolve the dilemma of ‘fitting people to
machines’ [12]. Anthropometry allows evaluation of the suitability of vehicle design for drivers [13]; designs that conform to users’ sizes in one country may not be
appropriate in other countries in which the users may be smaller or larger, so users may choose to modify the designs unilaterally [14].
2. Methods
2.1. Sampling and observation
In this study, the average dimensions for the seat pan, backrest and steering wheel were calculated from a sample of three buses. The layout of the seat and the
suspension system used were also observed. The seat design of the samples was assumed to be typical of the buses used in the Malaysian cities.
