This study from the University of Iowa examines ATV seat designs and their impact on crash risks, particularly focusing on passenger presence and the importance of seat length and placement for safety. Findings indicate significant variability in seat dimensions across different ATV models, and no industry-wide standards exist, contributing to rollover risks. The authors recommend implementing standardized seat design criteria to reduce fatalities and injuries linked to passenger use and age-inappropriate operation.

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.
electricmoto.com
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