Question 5 of 7: Individual Workplace Design and Work-Area Envelopes

Question 5: Individual Workplace Design and Work-Area Envelopes (20 marks: i–7, ii–7, iii–6)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

(i) Guidelines/Priorities for Individual Workplace Design

Individual workplace design applies the display-control priorities of Q2(iii) (primary visual tasks first, then the primary controls that interact with them, control-display compatibility, sequence, frequency, and consistency with other layouts) together with the importance/frequency/function/sequence arrangement principles, now to the whole workstation: place the items used most often and most critically within the easiest reach (the normal work area, see part ii); arrange items used in a fixed sequence in that operational order to minimize wasted motion; group by function so related tools/materials are together; design for the anthropometric range of the intended operators (5th–95th percentile, with adjustability preferred over a fixed compromise dimension); provide adequate clearance for posture change, ingress/egress, and any required personal protective equipment; and ensure the visual and control layout at the station (Q1–Q2) is compatible with the physical layout, so nothing the operator needs to see or reach is obstructed by something else on the bench.

(ii) Normal, Maximum, and Extreme Work Areas

The normal work area is the zone an operator can reach by sweeping the forearm across the work surface with the upper arm hanging naturally at the side (elbow as the pivot) — the region for the most frequent, repetitive hand motions, since it requires no shoulder movement or trunk lean. The maximum work area is the larger zone reachable by extending the whole arm from the shoulder (shoulder as the pivot), used for occasional reaches to less-frequently-needed items; working repeatedly at this radius is markedly more fatiguing than working within the normal area. The extreme (or extended) work area goes beyond the maximum arm-reach envelope by additionally allowing trunk lean/twist or a step, and should be reserved for rare access needs (e.g., an emergency stop reached only occasionally) rather than for any regularly repeated task element, since it both slows the reach and adds postural/balance risk.

(iii) Factors Affecting the Workplace Envelope

The reachable envelope at a given workstation is set jointly by: the operator's anthropometric dimensions (arm length, shoulder breadth, trunk mobility) across the design population; the work-surface height relative to elbow height, which shifts the whole reach envelope up or down; whether the task is performed seated, standing, or sit-stand (each posture changes the achievable reach radius and the comfortable envelope, per Q3(iii)); any obstructions on or near the surface (fixtures, guarding, adjacent equipment) that block part of the geometric reach envelope; the need for two-handed or bimanual work, which can require overlapping left- and right-hand envelopes rather than a single symmetric zone; and clothing/PPE (gloves, restrictive garments) that reduces effective reach and dexterity relative to the bare-handed anthropometric figures. Sanders & McCormick also single out the type of manual activity (a fingertip operation reaches farther than a full-hand grasp, which shrinks the usable envelope), the direction and height of the reach relative to the shoulder or seat reference point (the envelope is not a simple sphere), and any restraint on trunk or shoulder movement (e.g., a harness or seat belt) as factors that change the workplace envelope.