Gerene Denning, of the University of Iowa Department of Emergency Medicine presented this at CPSC's ATV Safety Summit Oct. 12, 2012. Objectives: Determine the variability of seat design for adult single-person ATVs. Methods: We measured seat placement and length for 77 ATV models (sports and utility) at dealerships and using a novel image-based method. Results: Seat lengths varied from 20-37 inches with significant differences between sport and utility models and between manufacturers. 75% of all seat backs ended near/over the rear axle. Longer seats generally resulted in shorter distances from the handle grips to the front of the seat (distance range 3.3-19 inches). An incline/decline study showed that a rider going downhill should shift his seat to near the rear axle with fully extended arms to avoid a forward rollover. Leaning forward from a normal seated position is sufficient to keep the center of gravity ahead of the rear tires and prevent a backward rollover when riding uphill. Conclusions: A wide variability in seat length was observed. Seats starting closer to the handle grips allow smaller children to be in front of adult drivers, or allow younger drivers. A shorter seat starting further from the handlebars and not extending beyond the rear axle would reduce the space available for passengers. Seat design is a potentially valuable approach to ATV-related injury prevention.
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ATV Safety Summit: Vehicle Tech Innovations - Optimizing Seat Design to Reduce Risk of All-Terrain Vehicle Crashes
1. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Optimizing Seat Design
To Reduce Risk
Of All-Terrain Vehicle Crashes
Charles Jennissen, MD Daniel McGehee, PhD
Gerene Denning, PhD Thomas Schnell, PhD
Nathan Miller Jonathon Marsico, BS
Kaiyang Tang John Steffen, MS
Department of Emergency Medicine University of Iowa College of Engineering
University of Iowa Carver College of Medicine
Slide 1
2. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
All-Terrain Vehicles (ATVs)
Utility ATV Sports ATV
Slide 2
3. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Single-Person Design
Most ATVs are designed and recommended
for use by only one person at a time.
Slide 3
4. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Long ATV Seats
However, many ATVs have long seats that appear large
enough to accommodate passengers.
The presence of extra riders increases the likelihood of a
crash, especially rollovers and ejections.
31% of victims in fatal crashes are operators with
passengers or passengers themselves.
Slide 4
5. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Objectives of Study
To define the characteristics of ATV seat size and
placement for existing makes and models.
To determine whether there was a design that would
allow for proper “active riding” while reducing the
likelihood of:
• Multiple riders.
• Age-inappropriate
operation
Slide 5
6. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Methods
Analyzed ATV seat dimension
requirements in a 26 degree
incline/decline study
Performed measurements for a
convenience sampling of ATV
models at several dealerships.
Developed and validated a
Photoshop™-based measurement
method.
Slide 6
7. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
INCLINE/DECLINE STUDY
RESULTS
2006 John Deere Trail Buck
650 cc ATV.
6.0 ft. (183 cm) male
Slide 7
8. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Incline/Decline Study
When going downhill, a rider must:
• Fully extend arms
• Move bottom back on the seat
Result= Moving body back on seat keeps center of
gravity behind the front tires to avoid a front rollover.
Slide 8
9. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Incline/Decline Study
When going uphill, a rider must:
• Lean forward while bending
their arms.
• No shifting forward on the
seat is normally required.
Result = Leaning forward sufficiently shifts center of
gravity ahead of the rear tires to prevent a backward
rollover.
Slide 9
10. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Steeper Inclines
With significant uphill
inclines, many experts
suggest standing and
leaning forward to position
your weight towards the
front wheels.
Slide 10
11. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Passengers
Passengers prevent these
weight shifting requirements
A passenger in front of the
rider, like a child, will not
allow the rider to lean
forward when going uphill.
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A passenger behind the
rider will prevent the rider to
move back on the seat
when heading downhill.
Both scenarios increase the
probability of a roll-over.
Slide 11
12. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Preliminary Conclusions/Hypotheses
Active riding requires shifting the operator’s center of
gravity on inclines/declines.
The rear edge of the seat
should be near the rear axle
(prevent forward rollover).
The seat does not need to extend forward toward the
handle grips beyond what will comfortably
accommodate an adult rider (prevent backward
rollover).
Slide 12
13. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
ATV MEASUREMENTS AT
DEALERSHIPS-
PILOT STUDY RESULTS
Slide 13
14. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Results
The seats of fourteen adult-sized utility and sport ATV
models from five major distributors were measured.
Engine Size Handle Stem to Front Seat Handle Stem to Back
Make Model Year (cc) of Seat (in.) Length (in.) of Seat (in.)
Utility
Bombardier John Deere Buck 2006 650 14 29 43
Polaris Trail Boss 2010 330 9 35 44
Polaris Sportsman 2010 500 11 29.5 40.5
Polaris Sportsman 2010 800 11 29.5 40.5
Polaris Sportsman 2010 850 10 31 41
Yamaha Grizzly 2010 350 17 23 40
Yamaha Grizzly 2010 450 17 22 39
Yamaha Grizzly 2010 700 19 22 41
Honda Rancher 2010 420 14 24 38
Honda Rubicon 2010 499 17 26 43
Honda Ricon 2010 675 16 27 43
Kawasaki BruteForce 2010 750 14 31 45
Sport
Yamaha Raptor 2010 700 12 31 43
Yamaha YFZ450R 2010 450 10 32 43
Slide 14
15. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Pilot Results
Seat lengths varied from 22-35 inches in length.
The back of the seats ended fairly consistently at 38-
45 inches away from the handlebar attachment.
Most of the difference in seat lengths was accountable
by the distance from the handlebar attachment to the
front of the seat which varied from 9-19 inches.
Slide 15
16. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
ATV MEASUREMENTS WITH A
ADOBE PHOTOSHOP™-BASED
METHODOLOGY
Slide 16
17. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Methods
Developed a novel Adobe Photoshop™-based
methodology to measure lengths and distances.
Performed measurements on 77 new ATV models from 8
manufacturers using downloaded images.
6
X X
Slide 17
18. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Methodology Validation
This methodology was
validated by:
Comparison with direct
measurements at dealerships
(N=12, Pearson
correlation coefficient 0.95 )
Comparison of results from two
independent measurers (N=20,
Pearson correlation coefficient
Enter
0.96). wheelbase
dimension
The average error ± SD in in “Length”
box.
calculated vehicle length
was 1.8% ±1.2%.
Slide 18
19. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Seat lengths on adult ATVs are highly variable.
Polaris has the
longest seats.
Arctic Cat has the
shortest seats.
Slide 19
20. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Sports ATVs have longer seats than utility ATVs.
N=21 N=46
Sports ATV
Utility ATV
Slide 20
21. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Sports ATVs have longer seats than utility ATVs.
Polaris
Trail Boss
Slide 21
22. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Seat Length and Engine Size (No Correlation)
Slide 22
23. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Seat Length by Wheelbase and ATV Style
Weak Positive Correlation
Slide 23
24. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Seat Length by Wheelbase and ATV Maker
Weak is >0 to <0.3
Moderate is 0.3 to <0.7
Strong is 0.7 and higher
Make Pearson r Correlation
Polaris -0.54 moderate negative correlation
Arctic Cat -0.37 moderate negative correlation
Can Am -0.31 weak negative correlation
Honda -0.08 no correlation
Yamaha +0.17 weak positive correlation
Kymco +0.44 moderate positive correlation
Suzuki +0.74 strong positive correlation
Kawasaki +0.87 strong positive correlation
Correlations varied greatly.
Slide 24
25. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Seat Placement-Arctic Cat
Slide 25
26. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Seat Placement-Polaris
Slide 26
27. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Summary of Results
Seat lengths for adult-sized vehicles ranged from 20-37
inches.
75% of all seat backs ended near or over the rear axle.
Shorter distances from the handle grips to the front of the
seat generally resulted in longer seats.
This distance ranged from 3.3-19 inches.
Slide 27
28. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Overall Results
Our results demonstrate that there are no industry-wide
standards for seat length and placement.
No apparent consistency in ATV seat design safety
consideration.
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Slide 28
29. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Conclusions/Hypotheses
Passengers and use by under-age operators are major
risk factors for ATV-related deaths and injuries.
Slide 29
30. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Conclusions/Hypotheses
Standardized criteria for seat length and
model-appropriate seat placement
should be implemented.
• Starting seats further from handle grips.
• Ending seats not further than the rear axle.
Such steps could improve safety by:
• Reducing likelihood of passengers.
• Reducing likelihood of age-inappropriate
operation.
Regulations may be needed to ensure
seat design changes are incorporated
throughout the industry.
Slide 30
31. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Questions?
Slide 31
32. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Photoshop™ Methodology
Vanishing
Point First steps:
•Download quality image
•Mark near hubs
6
•Identify vanishing point
X X
•Connect vanishing point and
near hubs
Next steps:
• Identify and mark far hubs (circle method)
• Find center of axles
Slide 32 Midpoints
33. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Photoshop™ Methodology
Final steps:
• Create plane through center of axles.
• Set scale by entering manufacturer wheelbase dimension.
• Draw vertical lines in plane.
• Measure between vertical
lines.
• Total = 77 models
• Measurer 1 vs. Measurer 2
(20 models)
• Photoshop vs. In-field
Enter
wheelbase
dimension in
Slide 33
(12 models) “Length” box.
34. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Error
[Absolute (Measured vehicle length-Manufacturer vehicle
length)]/Manufacturer vehicle length] expressed as %.
97 measurements (77 Measurer 1 + 20 Measurer 2)
The average error ± SD in calculated vehicle length was
1.8% ±1.2%.
Slide 34
35. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Measurer 1 vs. Measurer 2
40 Pearson r = 0.95 = Strong positive
p<0.0001
36
32
28
24
20
20 24 28 32 36 40
Seat Length (Measurer 1)
Slide 35
36. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Measurements at Dealerships
N = 12 models also done by the Photoshop™ Method
Build measuring device.
Lengths and distances
• Left end of device
placed at leftmost
point.
• Keeping level, right
end of device placed
at rightmost point.
• Clamps tightened and ruler used to provide
measurement.
Slide 36
37. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Photoshop™ vs. In-field
40 Pearson r = 0.95 = Strong positive
p<0.0001
36
32
28
24
20
20 24 28 32 36 40
Seat Length (Photoshop)
Slide 37
38. University of Iowa Hospitals and Clinics
Department of Emergency Medicine
Adult ATVs have longer seats than youth ATVs.
However, both have seats long
enough to accommodate a
passenger.
Adult Youth
N 67 10
Mean (SD) 27.8 (3.9) 24.5 (2.5)
95% CI 26.8, 28.7 22.7, 26.2
Median 28.1 24.2
Min 19.8 21.1
Max 37.0 29.2
t test P = 0.013
Slide 38
Notas do Editor
All-terrain vehicles have 3, 4, or 6 wheels. Some side-by-sides have roll cages and safety harnesses.