M.Y. Rosnaha et al. AJE Vol.9 2009 1-17
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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.
Development and Evaluation of Bus Seat Dimension to Improve the Fit and Comfort of Malaysian Bus Drivers
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2.2. Anthropometry data of bus drivers
A cross-sectional study was conducted to measure the anthropometric dimensions of Malaysian Commercial Vehicle Bus Drivers Table 1. A total of 176
bus drivers from seven bus depots in the Klang Valley serving the capital city participated in the study. Twelve anthropometric parameters were measured using
Martin’s type anthropometer; however, only ten were relevant to the seat design:
• buttock-popliteal depth; 1
• sitting eye height; 2
• weight; 3
• shoulder height; 4
• elbow-rest height; 5
• knee height; 6
• popliteal height; 7
• hip breadth; 8
• buttock-knee depth, 9
• and lumbar support height.10
2.3. Body part symptom survey
Twenty five drivers who used these seats were interviewed to identify any musculoskeletal pain that might be related to the design of the seat used. A body
part symptom figure was used based on the sitting posture; drivers were asked to indicate the body parts experiencing problems, i.e., neck and head, shoulder, upper
back, arm and hand, lower back, thigh, knee and ankle and leg. The frequency of the response for each part was calculated.
2.4. Modeling and evaluating the seat design
Seat designs were then modeled using CATIA software version V5R14. The CATIA software was used to design and simulate the current and recommended
seat using the anthropometric dimensions of the bus drivers. The Rapid Upper Limb Assessment RULA tool available in the software was used to give a quick
assessment of the potential problems that bus drivers may encounter with each seat design and to justify the need for a better seat design.
2.4.1. RULA analysis
RULA [15] is an ergonomic technique for evaluating individuals’ exposures to postures, forces and muscle activities that have been shown to contribute to
Repetitive Strain Injuries RSIs. Use of this ergonomic evaluation approach results
