Transportation Safety for Wheelchair Occupants - Part 2

This is the second part of a 90 slide lecture.

Go back to Part 1 (the first 30 slides)

Go ahead to Part 3 (the last 30 slides)


Pelvic Restraint Fit

Slide 31: Pelvic restraint fit

Slide text:

  • Snugly over the bony parts and across front of pelvis
  • ‘Belt junction’ near the hip
  • Not across abdominal area
  • Not over the wheelchair arm rests
  • No twisted belt assembly

Graphic description:

Pictures showing the recommended optimal angles and zones for the pelvic restraint.


Occupant Restraint Safety

Slide 32: Occupant restraint safety

Slide text:

  • Improperly positioned pelvic belt:
    • Abdominal injury due to ‘submarining’
    • Lumbar vertebra injury in frontal crashes
  • Improperly positioned shoulder belt:
    • Excessive head excursions
    • Secondary impact with vehicle surfaces
    • Injuries to vital thoracic cavity organs

Occupant Restraint

Slide 33: occupant restaint

Slide text:

“Best Practices”
  • Use both pelvic and shoulder belt to restrain the occupant
  • Lead restraints over bony anatomy
    • Shoulder restraint over the Sternum
    • Pelvic restraint over the (pelvis) Iliac Crests
  • Avoid loading soft tissues (abdomen)
  • Remove belt slack
  • Use a retractor to reduce upper torso belt slack
  • Restraint pre-tensioner reduces belt loading

Common Problems

Slide 34: Common problems

Slide text:

  • Shoulder belt slip off user’s shoulder
    • Due to shallow angle of torso belt
  • Shoulder belt rubs against user’s neck
    • Discomfort,
    • Resistance to using belt
    • Decreased upper torso restraint
  • Anchoring upper torso restraint below shoulder may result in downward loading of torso and spine.

The Real World

Slide 35: The real world

Graphic description:

Picture showing a child sideward facing in a wheel clamp system. NOT RECOMMENDED!!

4-Point Tiedown Systems

Slide 36: 4-point tiedown systems

Graphic description:

Pictures showing 4-point tiedown systems that are touching the tires, and are twisted. NOT RECOMMENDED!!

Occupant Restraints & Postural Supports

Slide 37: Occupant restraint & postural supports

Graphic description:

Pictures showing poor restraint fit (shoulder belt slides from the shoulder). Picture showing a pelvic belt that is wrapped over the wheelchair armrest and not restraining the occupant properly. The shoulder belt is not used but instead a postural support is used. NOT RECOMMENDED.

Possible Solution

Slide 38: Possible solution

Slide text:

  • Automated Wheelchair Securement
    • Universal docking approach
  • Seat Integrated Occupant Restraint System
    • Customized upper torso and pelvic restraint

Docking Interface

Slide 39: Docking interface

Graphic description:

Pictures showing the comparison between a car trailer-hitch and a wheelchair docking interface.


Effect of UDIG location on Wheelchair and Occupant Kinematics

Slide 40: Occupant kinematics

Slide text:

  • Securement point location on WC
    • Rear tie-down close to WC center of gravity
    • Location too low: forward wheelchair and occupant rotation during frontal impact
    • Location too high: rearward wheelchair rotation during frontal impact

Numerous Wheelchair Designs

Slide 41: Numerous Wheelchair Designs

Graphic description:

Pictures showing various types of wheelchairs, with all their differences and difficulties of attaching a UDIG to.


Only 1 interface geometry

Slide 42: Only 1 interface geometry

Slide text:

  • Need for standardization
    • ISO 10542-3 (docking type securement)
    • Use with all wheelchair types
    • Use with multiple docking stations
  • Universal Docking Interface Geometry requirements:
    • Specific dimensions
    • Clear zones

Specifications for vertical and horizontal location of a UDIG adaptor on the rear of a wheelchair

Slide 43: Specifications for vertical and horizontal location of a UDIG adaptor on the rear of a wheelchair

Graphic description:

Graphic of technical engineering drawing of the front and side view of the geometries of a wheelchair interface needed for automated wheelchair securement.


Specification of clear zones that allow access to the UDIG adaptor (max width)

Slide 44: Specification of clear zones that allow access to the UDIG adaptor (max width)

Graphic description:

Graphic of technical engineering drawing of the front and side view of the geometries of a wheelchair interface needed for automated wheelchair securement.


Docking System Technology

Slide 45: Docking system technology

Slide text:

  • Ongoing research at the University of Pittsburgh’s RERC on Wheelchair Transportation Safety
  • Standards development

Wheelchair Mounted Restraint

Slide 46: Wheelchair mounted restraint

Slide text:

  • Improved occupant restraint
  • Customized restraint
  • Ease of use
  • Increased wheelchair strength
  • Added wheelchair weight

Feasibility

Slide 47: Feasibility

Graphic description:

Picture that shows a 50th percentile male dummy in a wheelchair setup. The dummy is restrained by a wheelchair mounted (integrated) occupant restraint system.


Comparison Study

Slide 48: Comparison study

Graphic description:

Graphic comparison between a vehicle mounted and a wheelchair integrated occupant restraint system.


Wheelchair Mounted Restraint

Slide  49: Wheelchair mounted restraint

Slide text:

  • Ongoing research at the University of Pittsburgh’s RERC on Wheelchair Transportation Safety

Caster Crashworthiness

Slide 50: Caster Crashworthiness

Slide text:

  • Failure of caster assemblies was observed during sled impact testing (20g/30mph)
    • Light weight manual wheelchairs
    • Heavier power-chairs
  • Uncontrolled caster/fork failure may result in:
    • Abrupt high chest loading
    • Excessive forward movement
    • Submarining risk when using vehicle mtd. occupant restraints

Caster-Fork Assembly Loads

Slide 51: Caster-fork assembly loads

Slide text:

  • Affected by:
    • Occupant weight
    • Wheelchair design (Power/Manual)
    • Seating system crashworthiness
    • Wheelchair securement location (high/low)
    • Occupant restraint scenario (vehicle vs. wheelchair mounted pelvic/shoulder belt)

Graphic description:

Pictures showing various caster wheels and caster forks.


Test Setup

Slide 52: Test setup

Slide text:

  • Sledpulse: 20g/30mph
  • 50th percentile male Hybrid III ATD
  • Surrogate wheelchair base
  • Vehicle mounted occupant restraint system
  • Varying seat and back surfaces
  • Varying wheelchair securement point location

Test Setup: Caster Load Cells

Slide 53: Test setup: Caster load cells

Graphic description:

Pictures showing the sled test platform with integrated load sensing plates to record caster wheel loading during frontal impact.


Caster Load Direction

Slide 54: Caster load direction

Graphic description:

Picture showing the caster loading during frontal impact.


Peak Loads

Slide 55: Peak loads

Graphic description:

Table that shows the various wheelchair and seating system setups, failures, and recorded normal and shear loads from the load sensor.


Pendulum Impact Tester (PIT)

Slide 56: Pendulum Impact Tester(PIT)

Slide text:

  • Development of a dynamic test to determine:
  • Caster failure
  • Caster loading
  • Caster deformation
  • Energy absorption

Conclusions

Slide 57: Conclusions

Slide text:

  • Results from PIT resembles dynamic impact test data
  • Similar load patterns
  • More caster and fork testing ongoing for validation test method

In addition:

  • Computer simulation used to develop crashworthy casters

Wheelchair Crashworthiness

Slide 58: Wheelchair crashworthiness

Slide text:

  • Wheelchairs:
    • designed to provide mobility to individuals
    • not designed as automobile seats
  • Wheelchair Seating system (WCSS):
    • Unknown level of occupant protection under impact
    • Substitute-seating systems will not be sled tested by ANSI/RESNA WC/19

Graphic description:

Wheelchairs are designed to provide mobility to individuals and not designed as automobile seats,so, in many cases, the level of protection that wheelchair and its seating systems can provide under impact is unknown.

WCSSs are often provided as add on or replacement products after the wheelchair has been in the field, so they will not be sled tested by the ANSI/RESNA WC/19 standard.Therefore, as part of wheelchair transportation safety researches, crashworthiness of wheelchair seating systems have been also evaluated.


Wheelchair Seating System (WCSS) Crashworthiness

Slide 59: Wheelchair Seating System (WCSS) Crashworthiness

Graphic description:

Wheelchair Seating System includes wheelchair seat surface, back surface, and their attachment hardware.


WCSS Static Tests – Applied Forces

Slide 60: WCSS static tests-Applied forces

Slide text:

  • Computer crash simulation
    • Loads exert on a wheelchair subjected to a 48 km/h (30mph)/20g frontal crash
    • 50th percentile male Hybrid III model and four-point belt tie-down system
  • Mathematical Calculation

Graphic description:

We first conducted a static test of WCSSs to simulate the loading on wheelchair seating systems (WCSSs) during a impact.Compare to a dynamic sled test, static test is low cost, and we believed that the potential failure of a seating system product can be detected through a static test.

The forces applied to the seating systems in static test were determined using computer simulation and mathematical calculation.


This is the end of the middle part of a 90 slide lecture.

Go back to Part 1 of the slide lecture (the first 30 slides)

Go ahead to Part 3 of the slide lecture (the last 30 slides)

Comments