23-Ind-B5 Ergonomics · December 2018
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — Dec. 2018 — 17-Ind-B5 Ergonomics. Three-hour, open-book exam (any non-communicating calculator permitted); NIOSH lifting tables (Appendix 1) and a manual-materials-handling assist-device table (Appendix 2) are supplied on the exam's own pages. The paper's instructions state a total of four questions: Part A (Questions 1–2) is mandatory, Part B asks the candidate to choose one of Questions 3 or 4. All four questions are solved below.
Reference texts: Sanders & McCormick, Human Factors in Engineering and Design (7th ed.) — environmental ergonomics, human-factors analysis methods, error taxonomy (Reason's model), and controls/displays population-stereotype/spatial-compatibility principles (incl. the classic Chapanis & Lindenbaum stove-burner control-panel study); Waters, Putz-Anderson & Garg, NIOSH Applications Manual for the Revised NIOSH Lifting Equation (1994) — the RWL/LI formula and multiplier tables reproduced on the exam's own Appendix 1; NIOSH, Elements of Ergonomics Programs (1997) and CSA Z1004 (Canada) — workplace musculoskeletal-disorder (MSD) prevention programs; CSA Z1002 — hazard identification, elimination and risk assessment.
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.
Reason's model (Fig. 2) traces an action from a stimulus through interpretation/situation assessment and plan/intention of action (drawing on memory) to action execution, with a feedback loop back to interpretation. Mistakes are planning errors – the wrong intention is formed at interpretation or planning (the intention is carried out correctly, but it was the wrong intention); slips are execution errors – the intention was correct but the action itself goes wrong; lapses and mode errors are memory failures – a step is omitted or the wrong stored routine is triggered. The model is also commonly extended with a fourth category, violations – a deliberate deviation from a known safe procedure, which is not a processing failure at all and therefore does not map onto any box in Fig. 2.
| # | Error | Type | Justification |
|---|---|---|---|
| 1 | Hauler not returned for service on schedule | Lapse | An administrative/memory failure – the scheduling step is forgotten or not triggered at the right time, not a wrong decision or a botched action. |
| 2 | Setting off with parking brake on | Lapse (omission) | The release-brake step of a well-learned start-up sequence is skipped from memory; the intention (to drive off) and the executed action (drive off) are both otherwise correct. |
| 3 | Driving while sitting on the rear bumper | Violation | A deliberate departure from a known safe operating procedure (operate from the seat) – not a processing failure, so it falls outside Reason's error boxes entirely. |
| 4 | Misreading of displays | Slip | A perceptual/execution error at the interpretation stage of an otherwise correct plan – the operator intends to read the display correctly but the perceptual act goes wrong (a description-type slip). |
| 5 | Leaning out of cab while travelling | Violation | A deliberate unsafe act (usually for a better sightline), performed knowingly rather than by mistake or memory failure. |
| 6 | Insufficient warning while backing up | Mistake (rule-based) | Reflects a habitually wrong or incomplete procedure for backing up (an incorrect “if-then” rule being applied), rather than a one-off slip – the plan itself is deficient. |
| 7 | Instability prevents effective fire-extinguisher use | Not a human error – design/engineering deficiency | This is a property of the machine/mount design, not a human action at all, so it does not fit any box of Reason's operator-error model; it needs an engineering fix, not a human-factors intervention aimed at the operator. |
| 8 | Incorrect operation of machine controls | Mistake (rule-based) or slip | If the operator consistently uses the wrong control sequence, it is a rule-based mistake (wrong learned procedure); if it is an occasional wrong-button action despite correct intent, it is a slip – distinguishing the two requires observing whether the error repeats systematically or occurs sporadically. |
| 9 | Tires not maintained per accepted practice | Lapse / organizational | Like item 1, a scheduled-maintenance step omitted from an administrative memory system, rather than an in-cab operating error. |
| 10 | Operating too fast when fully loaded | Violation | A known speed limit for the loaded condition is knowingly exceeded – a deliberate risk-taking act, not a slip, lapse or mistaken plan. |
Interventions are matched to the error mechanism identified in Part (a), since a single blanket fix (e.g. “more training”) does not correct every category:
[Figure not reproduced: Fig. 3 — Reason's model of human error (1991), redrawn per the source Figure 2: mistakes originate at interpretation/planning, slips at action execution, and lapses/mode errors from memory. See the official exam paper.]
