The Effect of a Wheelchair Integrated Occupant Restraint System on Wheelchair Tie-down and Occupant Restraint Design Characteristics
Linda van Roosmalen PhD
Linda van Roosmalen PhD
ORS are used for:
FWORS use could result in:
From the occupant restraint survey, observation and belt fit study and the literature, the problem can be stated as follows.
FWORS are ineffective due to: varying occupant population and wheelchair designs and dimensions.
Varying location of the wheelchair in the securement zone.
Interference with wheelchair armrests, lap trays etc. and interference of the vehicle structure with restraint anchor installation.
Also, the use of FWORS appears to result in compromised belt fit for a varying occupant population, reduced user comfort, which may also cause individuals not to use restraints.
Finally, belts touching the neck or other soft areas may result in restraint related injuries during impact. And poorly positioned belts could cause occupant injury due to excessive forward movement of the occupant, or due to increased loads onto body parts such as the abdomen, chest and head.
To improve the safety and comfort of wheelchair Occupant Restraint Systems (ORS) when used in transportation
Wheelchairs are designed to provide mobility to individuals. Since many wheelchair users use their wheelchairs as motor vehicle seats, there is a growing demand for wheelchairs that can be safely used in transportation.
This means that design criteria need to be established for wheelchairs and occupant restraint systems. Design criteria in the areas of crash protection, seat design characteristics, usability and comfort.
This all needs to be done to provide individuals using a wheelchair comparable level of safety and user comfort as individuals seated in an original equipped and manufactured (OEM) vehicle seat and restraint system when exposed to crash conditions.
Graphic Description: a diagram with four arrows pointing from a picture of a wheelchair with occupant restraint system towards crash protection, usability, seat design and comfort.
(Haberl et al. @ BMW, Germany, 1989; Wainwright et al., 1994;
Cremer, 1986; Ruter & Hontschik @ Batelle Ins. Germany, 1979)
Prototype wheelchair integrated occupant restraint system (FEA)
Evaluate seat to back strength of wheelchair seating system (FMVSS 207)
Evaluate strength of seat belt anchors of a concept WIRS (FMVSS 210)
Evaluate capability of seating system and WIRS to withstand occupant restraint loads (WC-19)
Evaluate occupant safety (SAE J2249)
Optimize WIRS characteristics using computer simulation
Graphic Description: two pictures: one picture shows a solid model with loads at the bottom and top of the wheelchair integrated restraint structure. This solid model is used to run Finite Element Analysis. The other picture shows the actual prototype of the wheelchair integrated restraint system that was used for dynamic crash testing.
Graphic Description: front and rear view photographs of the WIRS on the surrogate wheelchair base used for dynamic sled testing.
Evaluating the seating system and occupant safety:
Dynamic Sled Impact Setup (20g/30mph)
Hybrid III 50th % male dummy (172.3lb)
Surrogate belt type wheelchair tie-down system
Wheelchair is secured with four point tiedown
WIRS versus fixed vehicle mounted ORS
Compliance with SAE J2249 and GM IARV’s
FWORS: Fixed Wheelchair Occupant Restraint System
Graphic Description: the FWORS picture shows the setup of the wheelchair and occupant restraint system. The occupant restraint system is attached to the exterior. A Hybrid III ATD is restrained by the FWORS
WIRS: Wheelchair Integrated Occupant Restraint System
Graphic Description: the WIRS picture shows the test setup of the wheelchair and occupant restraint system that is attached to the wheelchair itsself. A Hybrid III dummie is restrained by the WIRS.
Upper torso restraint location according to SAE J2249
Graphic Description: One picture is a drawing showing the side front and top view of a 50th percentile male wheelchair occupant seated in a wheelchair. This picture was taken from the SAE J2249 standard. It shows the optimal location of the shoulder belt anchor. The optimal anchor location is positioned 300 mm behind the shoulder, 173 mm above the shoulder and 300 mm from the centerline of the body.
WCSS on surrogate base
Graphic Description: the other picture is a photograph showing the surrogate base with the wheelchair seating system attached to it.
Graphic Description: two photographs showing the test setup of the fixed vehicle mounted occupant restraint system and the wheelchair that is secured with a 4-point tiedown system to the sled platform. An instrumented hybrid III dummy of a 50th percentile male is seated in the wheelchair and is restrained by a upper torso and pelvic belt which are attached to the sled platform and vertical post.
Graphic Description: a picture showing an actual video of sled impact test during frontal impact (30mph/20g).
Upper torso restraint anchor according to SAE J2249 and WCSS on surrogate base
Graphic Description: a picture showing the optimal upper torso restraint angle for a 50th percentile male as is used to determine the anchor location of the wheelchair mounted occupant restraint system which is shown in another picture on this slide. This wheelchair mounted occupant restraint system existing of a shoulder and pelvic belt is attached to a wheelchair seating system, which is again attached to the surrogate
Graphic Description: two photographs showing the test setup of the wheelchair mounted occupant restraint system and the wheelchair that is secured with a 4-point tiedown system to the sled platform. An instrumented hybrid III dummy of a 50th percentile male is seated in the wheelchair and is restrained by an upper torso and pelvic belt which are attached to the wheelchair seat frame.
Graphic Description: picture showing an actual video of sled impact test during frontal impact (30mph/20g).
Vehicle Mounted Restraint System and Wheelchair Mounted Restraint System
Graphic Description: a comparison of the two videos of the two different systems.
Graphic Description: This picture shows three screenshots of the moving dummy during frontal impact at 40, 80 and 120 milliseconds for the two different restraint scenarios.
Head (forward) excursion [SAE limit = 25.6 cm]
Knee (forward) excursion [SAE limit= 14.8 cm]
Graphic Description: Two graphs of the motion comparison of the two restraint scenarios: forward head excursion and forward knee excursion. Slide 20 will give a numerical overview of the differences between the two restraint scenarios.
Wheelchair (forward) excursion [SAE limit = 7.9 cm)
Graphic Description: graph of the forward wheelchair excursion. Slide 20 will give a numerical overview of the differences between the two restraint scenarios.
Graphic Description: a table consisting of five columns:
Mid sternum compression
Graphic Description: a graph of the Chest acceleration and a graph of mid sternum compression. The previous slide, Slide 20, gives a numerical overview of the differences between the two restraint scenarios.
Pelvic restraint load
Upper torso restraint load
Wheelchair Tiedown Loads
Graphic Description: graphs of the pelvic restraint load, upper torso restraint load and wheelchair tiedown loads for the two different restraint scenarios. Slide 20 gives a numerical overview of the differences between the two restraint scenarios.
Neck Flexion (C1 level)[GM/SAE limit = 1681 in-lb]
Neck axial load (tensile)[GM/SAE limit = 652 lb.<35ms]
Neck shear force (fore/aft)[GM/SAE limit = 337 lb.<25ms]
Graphic Description: graphs of the neck flexion, neck axial load and neck shear force of both restrain scenarios during frontal impact over 120 milliseconds. Slide 20 gives a numerical overview of the differences between the two restraint scenarios.
WIRS and FWORS compliance
This study is supported through:
Updated: March 14, 2002