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Design and evaluation methods in Human Factors Engineering

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Title: Design and evaluation methods in Human Factors Engineering


1
Design and evaluation methods in Human Factors
Engineering
  • Dan McGehee

2
Design process for human use a critical element
of overall system design
  • Usability
  • Safety
  • Efficiency
  • Economics
  • Should never stop in a products life cycle

3
The Gospel of Human Factors Design
  • Design for thy user, and you are not thy user

Wings stay on
Wings fall off
Fumbling for his recline button, Ted unwittingly
instigates a disaster
4
System development process
  • Front-end analysis--Early Focus on the user
  • User analysis--empirical measurement
  • Function analysis
  • Preliminary task analysis
  • Identify user preferences
  • Safety issues
  • Conceptual design
  • Function allocation
  • All initial design considerations must be
    supported with data

5
Systems development (cont.)
  • Iterative design
  • Task analysis (compared to initial state)
  • Tweak interface design
  • Simulations and modeling
  • Safety analysis
  • Usability testing
  • Design of support materials (same process!)
  • Manuals
  • Training
  • Production, implementation and evaluation
  • Evaluate use in the field
  • System operation and maintenance
  • Continually monitor use and iterate design

6
Design and evaluation of a lane awareness system
for snowplow operations
  • Daniel V. McGehee
  • Mireille Raby
  • University of Iowa

7
Background
  • Snowplow operators routinely face intermittent
    periods of very low, and on occasion, no forward
    visibility
  • Low visibility places snowplow operators at
    increased risk to
  • run-off-road
  • being struck from behind
  • Outcome can cause primary roads to be shut down
    for extended periods thus delaying commerce and
    the traveling public

8
Project objectives
  • Design
  • an operator interface increase lane awareness
    during snowplow operations
  • a simple and inexpensive product that easily
    integrates into a snowplow cab
  • an interface that can withstand a rugged
    environment
  • Use active, non-management drivers in all aspects
    of design

9
Design approach
  • Use a system-based approach
  • Complement existing environment-based visual cues
  • Support the drivers task without increasing
    workload
  • Provide warnings that are compatible with other
    in-cab systems

10
Infrastructure and hardware components
  • Magnetic Tape
  • Marks the pavement with a continuous magnetic
    reference line
  • Installed as underlay under asphalt or grooved
    into surface
  • If grooved, can be used as pavement markings
  • Vehicle-mounted sensors
  • Detects 3 feet from the center of magnetic tape

11
Vehicle-mounted sensor
12
Vehicle-mounted sensor
13
Overview of project phases
  • PHASE 1 - Understand operational user issues
  • Ride-alongs interviews
  • Survey of Iowa Minnesota DOT snowplow operators
  • PHASE 2 - Identify design requirements
  • Function allocation cognitive task analysis
  • Trade studies
  • PHASE 3 - Prototype design
  • Iterated with feedback from active snowplow
    operators hardware/software engineers
  • PHASE 4 - User testing
  • Test track and field testing
  • PHASE 5 - Final Design and product implementation
  • PHASE 6 - Track use and iterate for next version

14
Phase 1 -Understand Operational User Issues
  • Ride-along interviews
  • Conducted during snow storms in Iowa
  • Survey of operators
  • Based on the ride-along interview experiences
  • To obtain detailed operations and user data

15
Phase 1 - Survey details
  • 1678 surveys sent - 1009 were returned (60)
  • Distributed to active snowplow drivers from
  • Iowa DOT
  • Minnesota DOT
  • 48 questions examining
  • Operator demographics
  • Cab configuration vehicle type
  • Route information
  • Vehicle alarms and devices
  • Low-visibility operations

16
Phase 1 - Survey findings
  • Drivers use several cues to determine lane
    position
  • As forward visibility decreases - these cues go
    away
  • Center and shoulder line were judged most helpful
  • Center line recommended by drivers for display
    orientation
  • Intermittent loss of visibility (4-9 sec) is the
    most common event, compared to 30 sec
  • Longest duration 1 to 19 sec compared to 50 sec

17
Phase 1 - Survey findings (continued)
  • Drivers intentionally drive over the center and
    shoulder line 0-3 feet
  • Interviews found that operators are opposed to
    additional auditory alerts
  • Must be able to turn them off
  • Ambient noise is a factor (masking)
  • Annoyance
  • Drivers complained of in-cab control lighting
  • Some lights taped over in cabs
  • Window icing exacerbates visibility problem
  • Very continuous zero visibility is the exception

18
Phase 2 - Identify design requirements
  • Integrate ride-along interviews and survey
    findings
  • Allocate functions to automation levels
  • Identify demands on the operator
  • using Operator Function Model-Cognitive Task
    Analysis
  • to recommend display modalities and presentation
    information
  • using trade studies

19
Phase 2 - Operator function model-cognitive task
analysis
  • What it does
  • describes operational constraints and links them
    to the cognitive limits of drivers
  • helps identify critical functions and preliminary
    design criteria
  • In other words, it
  • identifies functions to be performed by the
    operator
  • specifies how functions are linked to each other
  • characterizes the cognitive and perceptual
    demands for various functions
  • eliminates or specifies design options

20
Phase 2 - Trade studies
  • Distills function analysis and survey data into
    viable design concepts
  • Four-step process
  • 1. Identify design parameters (e.g., display
    mode)
  • 2. Identify design constraints (e.g., visual
    demands)
  • 3. Weigh design constraints
  • 4. Rate design parameters for each design
    constraint

21
Phase 2 - Example of Trade Study
Visual Demands
Annoyance
Response Time
Implementation
Cost
Total
(10)
(9)
(8)
(7)
(6)
A Average Score AW Weight Average Score
A
AW
Modalities Visual - foveal - peripheral Auditory
- non-speech - speech Haptic - steering wheel -
seat
22
Phase 2 - Findings to forward to next phase
  • Few visual resources for a primary visual
    display
  • Needs to be a driver aid
  • Peripheral modalities preferred
  • All ambient light conditions for visual displays
    need be considered
  • Night time ops black background
  • Day time ops need to minimize impact of glare
    bright light
  • Should be selectable for left or right plow
    and/or sensor operations

23
Phase 3 - Fundamental design
  • Primary Cues peripheral modalities
  • Directional seat vibration on thigh bolster
  • Peripheral vision flashing lights (mounted high)
  • Secondary Cue a visual reference
  • a control/display unit for reference to adjust
    warning threshold and intensity

24
Phase 3 - Operator interface
Peripheral Warning Lights
Control Unit Visual Aid
Directional Seat Vibrations on Thigh Bolster
25
Haptic seat
26
Phase 3 - Control unit features
Warning adjustment Indicator
Warning adjustment indicator
Seat vib adjust
Moving pointer
Fixed scale
PVD brightness adjust
Lane Line ref.
System power
Warning threshold adjustment
Warning threshold adjustment
27
Phase 4 - User Testing
  • Surveys interviews in Michigan Arizona
  • Active snowplow operators currently using the
    system
  • Pre post-training surveys
  • Interviews at end of season
  • On-the-road testing at Mn/Road (Minnesota)
  • On-board vehicle with active snowplow operators
  • Vehicle performance data collection (microDAS)
  • Simulated low-visibility conditions (louver
    system)
  • Simulated right-wing plow operations and
    obstacles
  • Designed around constraints (e.g., visibility,
    test track)

28
Mn/Road Test Track
29
Low-visibility Louver System
30
Conclusions
  • A system-based approach
  • provides a quantitative framework to ensure all
    factors are considered
  • creates a design that is compatible with
    operators tasks, demands, and cognitive and
    physical limitations
  • might seem long and expensive, but less
    exhaustive approach may result in a product that
    is neither popular nor useful
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