Transportation Safety for Wheelchair Occupants

Linda van Roosmalen, PhDDouglas Hobson, PhD

Department of Rehabilitation Science and TechnologyUniversity of Pittsburgh

Funding: National Institute on Disability and Rehabilitation Research

March 2004ISS-Instructional Course

Application to practice

• Wheelchair transit and associated risks• Methods to prevent occupant injury• Safety guidelines and Standards• Resources

Wheelchair Transportation Safety• 1.6 million wheelchair users• Access to motor-vehicle transportation is the key to

functioning in society• ADA prohibits discrimination in public transportation

services• 2001 New Freedom initiative calls for integration of

disabled persons into workforce and community - “transportation” critical factor in meeting this priority

• 82% of wheelchair users indicate difficulty with using public transportation

• Wheelchair users have 10% higher unemployment rate

Impact Severity• Injury Risk:

– Proportional to velocity change– “Loading = velocity * body weight”

• Occupant Restraints protect by:– Prevent occupant ejection from vehicle– Prevent excessive occupant motion– Reduce occupant loading– Increasing time of energy exposure

Safety Guidelines1. Secure the wheelchair

2. Restrain the occupant

3. Remove loose accessories from wheelchair

4. Remove parts that can injure occupant during an impact– Lap trays, loose objects, postural supports,

communication devices, neck rings

Sled Impact Testing

Frontal30mph20g

Safety System #1• Secure the Wheelchair to the Vehicle

Wheelchair Securement Systems

– Four point strap type tie-downs– Docking systems– Other: wheel-clamps, hybrids– Rearward facing compartments (in large

buses)

Strap type tie-down system• Advantages

– Four securement points (improves crash response and stability)

– Adaptable to most wheelchair types

– No additional wheelchair hardware required

– Withstands crash forces

IMMI-Westfield (IN)

Strap type tie-down system• Disadvantages

– Invasion of personal space– Lengthy securement times– Requires operator/attendant for securement– Tiedowns easily misplaced or soiled– Lack of defined wheelchair securement

points– Requires operator training when securing a

variety of wheelchairs

Easy Accessible Securement Points

NO!!!

Easy Accessible Securement Points

YES!!!

Docking Systems• Advantages

– Quick securement times– Independent securement– Eliminates need for human

judgment of securement point location

– Minimizes error– Withstands crash forces EZ-Lock (Baton Rouge, LA)

Docking Systems

• Disadvantages– Requires add-on hardware– Requires adaptations to all wheelchair

types– Hardware adds weight and length– Hardware affects ground clearance– Fewer securement points (less stability

and control of crash response)

Wheel Clamps

Wheel Clamps• Disadvantages

– Unable to safely withstand crash forces– Not compatible with all wheel types– Requires attendant for securement

• Advantages– Fairly quick securement– Less invasive

Passive Restraint:Containment

Wheelchair is positioned rearward facing in the vehicle

Passive Restraint:Containment

• Easy to use• Quick• Non-constraining• Independent use

HOWEVER….• For use in ’low-g’ vehicles

only– More research is needed to

evaluate safety during emergency driving situations

(Van Hool, Belgium)

Safety System #2

• Restrain the Occupant– To vehicle and/or wheelchair

Lap belts mounted to wheelchair frames are generally for positioning purposes and NOT for

safety during transit!!!

Occupant Restraints Reduce Risk of Injury

• Prevent occupant ejection• Increasing time over which the

occupant comes to a stop– Decreasing deceleration or “G-loads”– Higher weight means higher loads!

• Decrease occupant forward travel– Reduce risk of occupant impact with

vehicle interior

Sled Impact Testing without use of Occupant Restraints

Frontal30mph20g

Sled Impact Testingwith proper Occupant Restraints

Frontal30mph20g

3-Point Occupant Restraint

Upper torso belt(shoulder belt)

Pelvic belt(lap belt)

Gorilla Car Seat

Carrie Bus Seat

Snug Seat Car Bed

Harness Type Restraint

EZ-On Vest

Occupant Restraint Safety

• 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

Adomeit & Heger, 1975; Leung et al., 1985

Occupant Restraint Problems

• Appropriate belt fit related to:– Shoulder belt anchor point– Pelvic belt anchor point– Wheelchair and occupant size– Location of wheelchair in securement

zone– Available clearance for belt placement

Common Problems

• 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

Occupant Restraint “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

Wheel clampsSideward facing position

4-Point Tiedown SystemsTwisted Belts Belt interferes with tires

Occupant Restraints& Postural Supports

• No use of shoulder belts•Pelvic belt over armrests

Ongoing Research

• Automated Wheelchair Securement– Universal docking

• Customized Occupant Restraints– Wheelchair integrated– Consumer friendly

Safety System #3

• Support the Occupant– Wheelchair seating system– Wheelchair frame– Wheelchair components