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THE ASSESSMENT OF USABILITY IN THE PROCESS OF DESIGNING AND SELECTING ASSISTIVE TECHNOLOGY FOR USE IN AGRICULTURAL SETTINGS . Development and Use of The Agricultural AT Usability Checklist NTW 2011. Robert W. Stuthridge M.Sc. (Health Ergonomics) PhD Candidate

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Robert W. Stuthridge M.Sc. (Health Ergonomics) PhD Candidate

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Robert w stuthridge m sc health ergonomics phd candidate


Robert W. Stuthridge

M.Sc. (Health Ergonomics)

PhD Candidate

Department of Agricultural and Biological Engineering

Purdue University

West Lafayette, IN 47907



  • Research questions

  • History of the Ag. AT Usability checklist.

  • Who does Ag. AT usability affect?

  • The checklist workshop:

    • Design of the checklist (Language, Aims and Format)

    • Filling out the checklist: Case studies

    • Feedback: reviews, comments, questions and suggestions.

Research questions

Research Questions

How do agricultural AT designers approach the ‘usability’ of AT design (and why)?

Is ‘ergonomics for one’ an appropriate approach if the AT increases injury risk for other workers?

What steps could be introduced to the design process to reduce injury risk related to Ag. AT?

How should these steps be formulated to be useful to any person engaged in the design of any AT for use in any agricultural setting?

History of the ag at usability checklist

Observed 5 AT Professionals on farm visits in 3 States. Possible issue defining ‘users,’ and considering their risk of injury as a result of implementing the AT.

15 interviews with AT professional designers, 8 interviews with farmers/ranchers who had independently designed and implemented AT. Coding (analysis)

History of the AG AT Usability Checklist

Coding and analysis nvivo 8 0

Coding and analysis: NVivo 8.0

Quick demonstration of NVivo

History of the ag at usability checklist1

Developed a decision chart of AG AT usability.

Developed checklist (1.0) to increase awareness of hazards to ‘users.’

Heuristic evaluation of checklist: 8 experts in usability: Ergonomists working in usability and/or documentation, and Usability Professionals (via Human Factors & Ergonomics Society and Usability Professionals Association). Led to Checklist (2.0)

Field testing of checklist by 9 AT professionals Checklist (3.0)

“Final” evaluation : workshop at NTW 2011.

History of the AG AT Usability Checklist

Who does ag at affect primary users

Who does Ag. AT affect? Primary Users

  • The AT ‘user’ is generally defined as ‘the client being assessed.’ The “PRIMARY USER.”

  • This influences the design process:

    • Often, the AT designer formally considers AT usability within an “ergonomics for one” paradigm

    • “The primary operator needs to use this piece of adapted equipment with ease and comfort;”

    • When selecting the AT, I “did not actively pursue” a consideration of the AT’s risk for other users’ injuries;

    • What steps did you take during AT design/selection to make sure the AT would be easy for people other than your client to use or operate? “None.”

    • “VR were going to have an OT come, but there is no physical effort now.”

Who does ag at affect secondary users

Who does Ag. AT affect? Secondary Users

RES: “Who, in addition to your client, might make use of the AT?”

  • “Her elderly father will make use of the ramp.”

  • “His fatherwill use the modified tractor;”

  • “Her husband probably would…it’s possible they would share the task, although it was designed for her – he’s much taller;”

  • “It definitely would also be used by two ranch hands, two guys;”

  • “It certainly would be used by her son, plus other ranch hands, but I’m not sure how many – at least two or three others.”

  • “Husband and son would be very likely to use it…”

  • “The sonuses the accumulator …”

  • “Very likely…his two sons…”

  • “Probably his wife will use it;”

  • “Very likely that the son, a migrant worker and some school kids will use it.”

  • It’s possible that his wife would use it; there’s a 4-H student, now at college, who helps some, but not so much now.”

  • I never asked, but that was his job; he’s the ranch owner, and that was his job.

At design hazards for users

AT Design Hazards for Users

  • AT may increase primary user’s risk of “secondary injuries,” and increase injury risk for other users – esp. slips, falls, incidental contact with AT. (Allen, Field et al. 1995; Willkomm 1997; Yoder, Kingman et al. 2001; Willkomm 2004; Mathew 2009).

RES: “How do you think that this step that you made might affect the ease with which people other than your client could operate the equipment?”

ATP: “I don't think it makes it harder to use, just maybe an annoyance if that step gets in their way. “

RES: “You mentioned before that sometimes, if they're in a hurry, they could forget that it was there. Presumably then if they forget it's there and then they stand on it and it moves…”

ATP: “Potentially they could trip and fall.”

Reducing risk to secondary at users

Reducing Risk to ‘Secondary’ AT Users

What steps did you take during its design/selection to make sure the AT would be easy for [secondary users] to operate?

  • “By default, my primary purpose/agenda is with my client; I always take care not to damage anyone else;”

  • “We spent so much time assessing both the primary user and his dad to make sure it worked for both of them;”

  • “They all tried it. If at all possible I get a vendor to show it, or to take them to other farmers using it already.”

  • “I’d seen the [AT] being used widely around here – I don’t think there’d be any problem;”

  • “I thought it wouldn’t get in the way [for other users], but in reality I’ve realized the farmers don’t want to use a lot of steps;”

  • “We really didn’t particularly look at [the ease of use] for other people;”

Development of the agricultural at usability checklist

Development of the Agricultural AT Usability Checklist

Decision diagram of ag at usability 2010

Decision diagram of AG AT usability (2010)

First draft of Ag. AT design – usability - decision diagram at NTW 2010:

“AT Usability – A Tentative Human Factors Model.”

At usability a tentative human factors model

AT Usability – A Tentative Human Factors Model



Define ‘User’ Who will use the AT?

Primary User

Known Secondary User(s)

Unknown Secondary User(s)

Injury/Health Risks from AT






Question: Might the AT

adversely affect user risk

in respect of human factors?


continue with intervention



Primary User

Known Secondary User(s)

Unknown Secondary User(s)


Posture; Force; Repetition; Vibration; Other

Risk Reduction Options

Change AT Design

aka “engineering”

Change User Behavior

e.g. training

Change Exposure

e.g. restrict use and/or users

Aspects of Usability

Decision diagram of ag at usability 2011

Decision diagram of AG AT usability (2011)

Following the 23 interviews, and 8 heuristic evaluations, the decision diagram was revised – more clearly reflects the distinction between primary and secondary users of AT.

Agricultural at usability decision tree

Agricultural AT - Usability Decision Tree

Who might reasonably make use of the AT, or perform tasks that are in any way affected by the use of the AT?

(Section B)

Primary Client ONLY

Client with a disability, for whom the AT is principally intended.

Primary Client AND Additional People (Known or Unknown to AT Designer)

E.g., Co-workers, family members, seasonal workers, temporary laborers, etc., who may either:

i) directly perform the modified task or use the modified equipment, and/or

ii) perform other tasks that may be altered in any way as a result of the use of the AT by the primary client.

Might the AT increase the primary client’s

risk of injury due to any of the hazards listed in

Section C1?

Might the AT increase any user’s

risk of injury due to any of the hazards listed in

Section C2?


Proceed to implement AT ‘as is.’

Not Sure

Not Sure

Obtain further information and expert assistance as necessary – see Section D.



  • Modify tasks to reduce risks. Obtain expert assistance as necessary. see Section D.

The ag at d esign process usability checklist

The AG AT Design Process (Usability) Checklist

  • The Checklist is in FOUR Sections

  • Section A: Defines terms, and describes the need for, and the aims of the checklist.

  • Section B: Who is affected by the AT?

  • Section C: What are the injury risks for affected user(s)?

  • Section D: Approaches to reduce injury risk:

    • Engineering,

    • Behavior,

    • Organization,

    • Collaboration.

Section a at defined for this checklist

Section A: AT Defined for this checklist

Section a ag at users

Section A: Ag.AT “Users”

Section a aims limitations

Section A: Aims & Limitations

At design as complex decision making

AT Design as Complex Decision-Making

  • AT designers select or design each AT solution within the context of a complex interaction of many influencing factors, including:

    • Personal and client motives;

    • Relationships with stake holders;

    • Economic constraints and motivations;

    • Background/experiences;

    • Training;

    • Relevant rules and regulations;

    • Awareness of solutions;

    • Context (social, physical, economic, political);

    • Awareness of hazards and risks…

  • This list is far from exhaustive – you might come up with many more factors that influence your design decisions!

At design as complex decision making1

AT Design as Complex Decision-Making

  • As humans, AT designers are able to arrive at decisions on “AT usability” based on injury risk information that is inevitably imprecise, incomplete, and uncertain.

  • No checklist could prescribe detailed solutions to maximize the usability of all AT in all situations – even if the checklist were of immense size.

  • The way this checklist works is by adding additional factors to the decision-making process. AT designers will readily find a way to incorporate these factors into their decision-making process – using their evolving “professional judgment.”

Section c hazard assessment


  • In the “professional judgment” of the AT designer, risk of injury from a hazard is either:



    The simplicity of this logic is reflected in the checklist’s two main questions:

  • Who will use the AT? (Section B)

  • Are there unacceptable hazards for users as a consequence of using the AT? (Section C)

    Responses to these two questions lead the AT designer to the next logical question:

    What might be done to eliminate unacceptable risk for AT users? (Section D)

Section d d1 engineering


  • Change the physical design of the AT so that it does not exceed users’ capacities.

  • Determine users’ relevant functional capacities, then match AT in terms of:

    • Dimensions

    • Shape

    • Construction materials

    • Operating forces

    • Design of controls (e.g. stereotyping, logic)

Section d d2 behavior

Section D - D2: BEHAVIOR

  • Change how people engage with the AT – e.g. hazard information/guidance, safety training, proper operation of modified equipment, proper performance of modified tasks.

Section d d3 organization


  • Changes to the organization of tasks: Work-rest schedules, job rotation, reassignment to alternative tasks.

Section d d4 collaboration


  • Collaborate or consult with a person qualified to advise on risk reduction interventions for the hazard in question.

    • Ergonomist

    • Occupational Therapist

    • Safety engineer

    • Mechanical or electrical engineer

  • The aim of collaboration is to obtain a relevant, independent, professional perspective.

  • Multiple specialists may be used, depending on the hazard.

Case studies

Case Studies

  • Groups of 4 to 5

  • 30-minutes maximum

  • 1 case study per group - you choose the case!

  • Determine who may be a “user” of the AT (B)

  • Determine potential unacceptable risks related to use of the AT (C)

  • Steps you might take to reduce injury risk (D).

  • Open (all groups) discussion of the checklist (especially faults and/or weaknesses, and suggested improvements).

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