Wheelchair Tiedown Loads and Occupant Restraint Loads Associated with Various Occupant Sizes in Frontal Impact Testing

DongRan Ha, MS & Gina Bertocci, PhD.
Injury Risk Assessment and Prevention Laboratory Department of Rehabilitation Science and Technology
University of Pittsburgh, Pittsburgh, PA

slide 1: Title and Authors

Background

slide 2: Backgroung

Slide text:

  • Increased number of wheelchair users relying on public and private transportation since ADA.
  • Wheelchairs must serve as vehicle seats for WC users who are unable to transfer to vehicle seats.
  • After market equipment is required to secure the WC to the vehicle and restrain the WC occupant.
  • Standards:
    • SAE J2249 – Wheelchair Tiedown and Occupant Restraint Systems (WTORS) for Use in Motor Vehicles
    • ISO 10542: Wheelchair Tiedown and Occupant Restraint Systems

Background

slide 3: Background

Slide text:

  • Information related to WTORS loading ‡ designing transport-safe wheelchairs, adapted vehicles and WTORS systems.
  • ANSI/RESNA WC19 - Wheelchairs Used as Seats in Motor Vehicles
    • tiedown loads, loads applied to securement points
  • On-board or integrated WC restraints
    • occupant restraint loads

Research objectives

slide 4: Research Objective

Slide text:

Summarize Wheelchair Tiedown and Occupant Restraint loading data during frontal impact sled testing for various size occupants.

Methods

slide 5: Methods

Slide text:

  • Review of 36 sled impact test reports from Convaid, a wheelchair manufacturer.
    • surrogate 4-point, strap-type tiedown to secure WC
    • a six-year-old ATD (21.8-30 kg), 5th percentile female ATD (45.5 kg), or 50th percentile male ATD (76.4 kg)
    • independent surrogate 3-point occupant restraint
    • the test was conducted under 20g/30mph frontal impact conditions.

Convaid = http://www.convaid.com/

ATD = anthropometric test dummy

Peak Tiedown Strap Forces with 6-year-old ATD

slide 6: Peak tiedown strap forces

Graphic description:

A bar graph shows the peak left-rear (represented with white boxes) and right-rear (represented with blue boxes) tiedown strap forces for the 6-year-old ATD tests.

The test number with the weight of the tested wheelchair are shown on the x-axis. The ‘Peak tiedown strap force’ in Newton is shown on the y-axis. The tiedown forces are presented in ascending order of the tested wheelchair.

General trend of the graph is that the peak tiedown strap forces increase as the weight of wheelchair increases.

Peak Tiedown Strap Forces with 5th %-tile Female ATD

slide 7: Peak tiedown strap forces

Graphic description:

A bar graph shows the peak left-rear (represented with white boxes) and right-rear (represented with blue boxes) tiedown strap forces for the 5th percentile female ATD tests.

The test number with the weight of the tested wheelchair are shown on the x-axis. The ‘Peak tiedown strap force’ in Newton is shown on the y-axis. The tiedown forces are presented in ascending order of the tested wheelchair.

The highest left-rear peak tiedown force, which is approximately 6000 N, occurred at the 13.2 kg wheelchair. The graph does not show any trend.

Peak Tiedown Strap Forces with 50th %-tile male ATD

slide 8: Peak tiedown strap forces

Graphic description:

A bar graph shows the peak left-rear (represented with white boxes) and right-rear (represented with blue boxes) tiedown strap forces for the 50th percentile male ATD tests.

The test number with the weight of the tested wheelchair are shown on the x-axis. The ‘Peak tiedown strap force’ in Newton is shown on the y-axis. The tiedown forces are presented in ascending order of the tested wheelchair.

The highest right-rear peak tiedown force, which is approximately 8000 N, occurred at the 13.2 kg wheelchair. The graph also does not show any trend.

Results

slide 9: Results

Graphic description:

The table shows the summary of the peak left-rear and right-rear tiedown strap forces for three different dummy sizes, 6-year-old, 5th percentile female and 50th percentile male.

All minimum, maximum, and average peak tiedown strap forces increase as the ATD size increases from 6-year-old to 5th percentile female to 50th percentile male.

Average peak tiedown strap forces are 4152 N (left) and 3626 (right) for 6-year old dummy, 4958 N (left) and 4693 N (right) for 5th percentile female dummy, and 6393 N (left) and 5782 N (right) for 50th percentile male dummy.

Peak Pelvic-belt and Shoulder-belt Loads with 6-year-old ATD

slide10: Peak pelvic-belt and shoulder-belt loads

Graphic description:

A bar graph shows the peak pelvic belt (represented with white boxes) and shoulder belt (represented with blue boxes) loads for 6-year-old dummy tests.

The test number with the weight of the tested wheelchair are shown on the x-axis. The ‘Peak belt load’ in Newton is shown on the y-axis.

The belt loads are presented in ascending order of the tested wheelchair.

All tests showed higher shoulder belt loads than pelvic belt loads.

Peak Pelvic-belt and Shoulder-belt Loads with 5th %-tile Female ATD

slide11: Peak pelvic-belt and shoulder-belt loads

Graphic description:

A bar graph shows the peak pelvic belt (represented with white boxes) and shoulder belt (represented with blue boxes) loads for 5th percentile female ATD tests.

The test number with the weight of the tested wheelchair are shown on the x-axis. The ‘Peak belt load’ in Newton is shown on the y-axis.

The belt loads are presented in ascending order of the tested wheelchair.

All tests showed higher shoulder belt loads than pelvic belt loads.

Peak Pelvic-belt and Shoulder-belt Loads with 50th %-tile Male ATD

slide 12: Peak pelvic-belt and shoulder-belt loads

Graphic description:

A bar graph shows the peak pelvic belt (represented with white boxes) and shoulder belt (represented with blue boxes) loads for 50th percentile male ATD tests.

The test number with the weight of the tested wheelchair are shown on the x-axis. The ‘Peak belt load’ in Newton is shown on the y-axis.

The belt loads are presented in ascending order of the tested wheelchair.

All tests showed higher shoulder belt loads than pelvic belt loads.

Results

slide13: Results

Graphic description:

The table shows the summary of the peak pelvic-belt and shoulder-belt loads for three different dummy sizes, 6-year-old, 5th percentile female and 50th percentile male.

All minimum, maximum, and average peak pelvic-belt and shoulder-belt loads increase as the ATD size increases from 6-year-old to 5th percentile female to 50th percentile male.

Average peak pelvic-belt and shoulder-belt loads are 2538 N (pelvic) and 3913 (shoulder) for 6-year old dummy, 3801 N (pelvic) and 7018 N (shoulder) for 5th percentile female dummy, and 6086 N (pelvic) and 9634 N (shoulder) for 50th percentile male dummy.

Conclusions

Slide 14: Conclusions

Slide text:

  • Wheelchair tiedown and occupant restraint loading data in 36 frontal impact sled test reports.
  • The average peak left-rear and right-rear tiedown strap loads:
    • 6-year-old ATD: 4152N and 3626N
    • 5th %-tile female ATD: 4958N and 4693N
    • 50th %-tile male ATD: 6393N and 5782N

Conclusions continued

Slide 15: Conclusion continued

Slide text:

  • The average peak pelvic-belt and shoulder-belt loads:
    • 6-year-old ATD: 2538N and 3913N
    • 5th %-tile female ATD: 3801N and 7018N
    • 50th %-tile male ATD: 6086N and 9634N
  • Results provide transport-safe WCs and WTORS manufacturers with design guidelines.

Acknowledgement

Slide 16: Acknowledgement

Slide text:

Thanks to Convaid for sharing the crash test results of their products.

Partially Supported by: NIDRR RERC on Wheelchair Transportation.

The End

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Updated: May 6, 2003

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Please note: This information is provided a archival information from the Rehabilitation Engineering Research Center on Wheeled Mobility from 1993 to 2002.

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