investigating novel speedometer displays to support speed tracking
TRANSCRIPT
Investigating novel speedometer displays to support speed tracking and
eyes-on-road driving
Assistant Professor Industrial & Systems Engineering Texas A&M University
Thomas Ferris
Piloting a vehicle
• Involves two concurrent “tracking” tasks: – Lateral position tracking – Longitudinal (or speed)
tracking
• Both tracking tasks require
focal visual resources
School zones
More eyes-on-road time?
• Reduce competition for focal visual resources: – Engage additional sensory modalities (peripheral vision, audition, touch)
• Support working memory
– Eliminate need to remember current speed limit – Eliminate the need to mentally calculate difference
between current velocity and target speed
Novel speedometer displays
• 3 designs: – Ambient visual – Auditory – Vibrotactile
• Communicate: – Whether current velocity is faster or
slower than designated target speed – Magnitude of difference between current and target
C-2 tactors Engineering Acoustics, Inc.
Am-Visual and Auditory displays
Display notes…
• All 3 displays featured 9 states
Speed (mph)
Ambient Visual (RGB codes)
Auditory (Hz)
Tactile (Location & Hz)
54> (153, 0, 0) 690+12 7, 8; 250+12 53 - 54 (255, 0, 0) 587+8 7, 8; 250+8
52 - 53 (255, 102, 0) 493+4 7, 8; 250+4
Acc rng
51 - 52 (255, 204, 0) 392+1 5, 6; 250+1 49 - 51 (255, 255, 102) 349 3, 4, 5, 6; 250 48 - 49 (187, 239, 57) 329-1 3, 4; 250-1
47 - 48 (0, 160, 0) 261-4 1, 2; 250-4 46 - 47 (0, 102, 255) 220-8 1, 2; 250-8 >46 (0, 0, 255) 174-12 1, 2; 250-12
Target speed: 50 mph
Display notes…
• Redundant encoding – Ambient Visual:
• Hue: “cold” colors for too slow, “hot” for too fast • Brightness: increase as approaching target
– Auditory: • Pitch: higher pitch for higher speeds • “Beat” frequency: sound “smoothes” (decreases in beat
frequency) to a pure tone as approaching target – Tactile:
• Position: vibrations presented near pelvis for too slow, near shoulders for too fast
• Pulse frequency: similar to auditory
Evaluation study
• 5-minute scenarios developed in STISIM Drive® – 4 equivalent, different scenarios:
• Number, angle, distance between road curves
• Longitudinal wind effects
• Within-subjects study – N = 12 (9 male; all with valid DL’s) – Completed 4 scenarios with different display conditions,
balanced order: baseline (traditional analog display only), 3 novel displays (each also included analog display)
– Performance measures and subjective ratings
Evaluation study
Performance measures: • Lateral position deviation • Speed deviation
– target speed: 50 mph • Acceptable performance percentage (AP%):
scenario time within “acceptable” range for both measures – 0.5 ft left of centerline < position < 0.5 ft right – 48 mph < speed < 52 mph
Results: Lateral position deviation
1.017 0.951 0.915 1.060
0.000
0.500
1.000
1.500
B V A T
Lateral Deviation (in feet)
No statistical difference
• Novel speedometers do
not impact eyes-on-road time…
• A few “slips” greatly impacted deviations
• Trend toward improvement for some displays
Results: Speed deviation
3.155
2.451 2.100
2.493
1.5002.0002.5003.0003.5004.000
B V A T
Speed Deviation (in mph)
B > V, A, T
• All 3 novel displays
improved speed deviation
• 33% improvement for auditory display over baseline
Results: AP%
V, A > B; A > T
0.200 0.266 0.282
0.229
0.100
0.200
0.300
0.400
B V A T
Acceptable Performance %
• ambient-Visual and
Auditory improved AP% over Baseline – Auditory: 41%
improvement
• Auditory better than Tactile
Results: Subjective preference
A most preferred, followed by T
3.417 2.667
1.833 2.000
01234
B V A T
Overall Preference (average ranking)
Attribute Ratings Sig.
Satisfaction A: 8.00; T: 7.50; V: 6.83; B: 4.92
< 0.001
Reliance A; 7.75; T: 7.58; V: 6.67 n.s.
Interpretation A: 6.50; T: 6.33; V: 6.08; B: 5.33
n.s.
Distraction A: 7.50; T: 6.75; V: 6.50; B: 3.67
< 0.001
Annoyance B: 8.00; V: 6.42; A: 5.67; T: 5.67
0.025
Discussion • Auditory and Tactile displays:
– best supported dual-tracking performance – were most preferred
• Results in accord with human information processing theory
– Multiple Resource Theory (Wickens, 2002): distribution of task-relevant stimuli among sensory channels can support improved multitasking
– Peripheral/ambient vision still affected by orientation of focal vision
• Ambient visual: – Backlighting not same as “ambient” lighting, can be distracting – Phototropism may have affected performance
Next steps • Evaluate encoding methods:
– Spatial encoding: where the visual, auditory, tactile signal is presented (e.g., “up” for higher speeds)
• Natural mapping for mental models or activation of controls – Symbolic encoding: what is the meaning of the signal (e.g.,
color coding or pitch/frequency-mapping) • Lane tracking heavily requires spatial working memory resources,
therefore symbolic may be more effective (e.g., Ferris & Sarter, 2010)
• Continuous analog mapping
• Redesign displays to improve usability and acceptance
• Vehicle-to-Infrastructure (V2I) communications, In-Vehicle Info Systems (IVIS) provide technological platform
• More eyes-on-road time
• Greater awareness of speed
Implications/Applications
