Project P3: Improved Design and Performance of Vehicle Restraint Systems for Frontal and Rear Impact Protection of Wheelchair-Seated Drivers and Passengers in Vans and Minivans

Task Leaders: Linda vanRoosmalen, Ph.D., Larry Schneider, Ph.D., Miriam Manary, MSE

Co-investigators: Nichole Ritchie, Nathaniel Madura, graduate students

Collaborators:  Jong-Bae Kim (wheelchair user) Pride Mobility (wheelchair manufacturer), Sure-Lok (WTORS manufacturer), Q'Straint (WTORS manufacturer), Creative Controls, Inc. (van modifier), Gresham Driving Aids (van modifier), A&A Driving School (school of driver trainers for the disabled)

Study Announcement and Consent Form

Overview

This project will address the long-term outcomes related to improved occupant protection and independence for wheelchair-seated travelers in personal vans and minivans. While both passengers and drivers are included in the scope, the primary emphasis will be on improving occupant restraint design and effectiveness for drivers, with a secondary emphasis on front-row passengers. The project will address front and rear-impact protection, primarily through improvements in the design of passive and wheelchair-integrated Wheelchair Tiedowns and Occupant Restraint Systems (WTORS).  However, it will also address issues of wheelchair design with regard to docking-type securement and with regard to accommodating the proper use and fit of WTORS.

The effort will be conducted over all five years of the RERC and is comprised of two primary tasks as follows:

• Task P3.1 - Investigation of WTORS Availability and Usage in Private Vehicles
• Task P3.2 - Development of WTORS for Improved Wheelchair User Restraint in Front and Rear Impacts of Private Vehicles

The project will begin with Task P3.1, an investigation of drivers and passengers seated in wheelchairs in their personal vehicles. The objective of this research effort is to more completely and objectively document the issues and problems surrounding the proper use of lap and shoulder belts, as well as frontal-impact airbags, by wheelchair-seated drivers and front-row passengers of private vehicles.

In years 2 through 5, the focus will shift to Task P3.2, a development task, which will be conducted in two phases. Part 1 will involve the development, demonstration, and evaluation of solutions for improving restraint effectiveness in frontal impacts. This work will be conducted in collaboration with wheelchair and WTORS manufacturers and van modifiers. It will involve the design and fabrication of innovative passive (no action required by the user) belt restraints for drivers, but it will also involve modifying existing powered wheelchairs so that they better accommodate the easy and proper placement of vehicle-anchored lap and shoulder belts.  This phase of the project will also include further evaluation and refinement of new concepts in seatbelt buckles developed in previous efforts, which allow people with disabilities to more easily don and doff vehicle- and wheelchair-anchored belts.  Issues related to improving both the operation and crashworthiness of forward-entry auto-engage docking stations for wheelchairs will also be addressed. 

In years 4 and 5, the effort will shift to Part 2 of Task P3.2, which will involve development relative to improving rear-impact protection for wheelchair-seated drivers and passengers, for which the level of occupant protection largely depends on the presence of effective head and back restraint. This part of the project will use the wheelchair geometry and rear-impact dynamic strength data collected in previous efforts to design and test a prototype, vehicle-mounted head/back support for use by wheelchair-seated drivers.

Expected Project Outputs and Short-term Outcomes

Expected Outputs

• Documentation and quantification of the issues and problems related to providing effective occupant restraint for wheelchair-seated occupants in private vehicles, with a particular emphasis on wheelchair-seated drivers,
• Workshops, conference presentations, and publications in peer-reviewed journals and consumer magazines that describe the problems and proposed solutions to providing more effective occupant restraint for drivers and passengers of personal vehicles in frontal and rear impacts,
• A WTORS standard with design/performance criteria and test methods for evaluating rear-impact protection,
• Prototype designs and demonstrations of new concepts for improved passive and active vehicle-anchored belt restraints,
• Demonstration of improved wheelchair and wheelchair seating system design features that provide for easier placement and improved fit of passive and active vehicle-anchored belt restraints,
• Evaluations of innovative buckle latching and release mechanisms for use by drivers and passengers with physical disabilities,
• Prototype designs for vehicle-anchored head and back supports that comply with the new TST standard, and
• Improvements in docking securement systems for wheelchair-seated drivers and front-row passengers

Expected Short Term Outcomes

• Safer and easier transportation options for occupants who use their wheelchairs as vehicle seats.

Project Updates

• Project P3.1: July 2012
• Project P3.1: July 2011
• Project P3.1: July 2010
• Project P3.1: July 2009
• Project P3.1: July 2008
• Project P3.1: July 2007
  
  
• Project P3.2: July 2012
• Project P3.2: July 2011
• Project P3.2: July 2010
• Project P3.2: July 2009
• Project P3.2: July 2008
  
  
• P3 Annual Report 2007 (2.3 MB pdf)

Task P3.1: Investigation of WTORS Availability and Usage in Private Vehicles

In the first year of this project, a detailed investigation of the restraint conditions for wheelchair-seated drivers and passengers will be conducted to more rigorously identify the likely sources of the problems beyond what is known from current anecdotal cases. It will also evaluate the potential negative consequences of these belt-restraint configurations and compare the injury risk to that of occupants with proper belt restraint in frontal crashes.

This will not be a traditional hypothesis-driven research study with statistical sampling on independent variables, and it will therefore not attempt to use any traditional experimental design techniques.  The only sampling criteria are that subjects use a private modified van or minivan and that they drive or ride in those vehicles while seated in their wheelchairs. However, a particular emphasis in recruiting subjects will be placed on the wheelchair-seated driver for whom it is believed that:

• lap and shoulder belts are rarely used or positioned in a manner that will provide effective restraint for drivers in a frontal crash
• changes to the design of powered wheelchairs and vehicle-anchored belt restraints are needed to improve the routing and performance of belt restraints on wheelchair-seated drivers
• rear-impact protection systems are minimal to non-existent for wheelchair-seated drivers in private vehicles
• the proximity of wheelchair-seated drivers to vehicle hand controls and the removal of airbag restraint systems to allow installation of these controls further increases the injury risk for these occupants

The data collected in each measurement session will be aimed at answering several questions, including:

• Q1: What are common types of (modified) occupant restraints, wheelchair securement systems, and hand/steering controls used by wheelchair-seated drivers and front-row passengers of private vehicles?
• Q2: What are the factors contributing to improper fit and use of belt restraints to wheelchair-seated drivers and front-row passengers in private vehicles?
• Q3: What are the specific geometric relationships between front-row wheelchair-seated occupants, belt restraints, and the vehicle interior and controls?
• Q4: How do wheelchair-seated drivers and front-row passengers rate their experience with private-vehicle transportation with regard to safety, usability, and independence?
• Q5: What changes would wheelchairs users of private vehicles like to see to improve travel in their vehicles?

Data collection will involve the following three parts:

1. An interview with the participant
2. Video recording of the wheelchair user entering and exiting the wheelchair station, including securement of the wheelchair and positioning of belt restraints
3. Measurement and photographic documentation of the seatbelt, occupant, and vehicle interior geometry with the wheelchair and seatbelts in their usual positions

P3.1: July 2012 Project Update

Work has continued on the publication of results. One manuscript is currently being reviewed internally for publication in JRRD, a peer-reviewed journal. The focus of this paper is on Summary of Occupant, Wheelchair and Wheelchair Tiedown and Occupant Restraint System Configuration Data for Wheelchair-Seated Drivers and Front-Row Passengers in Private Vehicles. One manuscript was accepted for publication in JRRD titled:
- L van Roosmalen, NR Orton and LW Schneider. Safety, usability and independence for wheelchair-seated drivers and front row passengers of private vehicles: A qualitative research study. Accepted for publication in Journal of Rehabilitation Research and Development, 2012.

These two papers address qualitative and quantitative documentation of the issues and problems related to providing effective occupant crash protection for drivers and passengers in private vehicles who stay seated in their wheelchair. They also document the current status of seat-belt fit and usage, and clarify the factors that prevent the use of properly positioned lap and shoulder belts on wheelchair-seated drivers. They report on wheelchair securement systems and driver controls, their locations relative to the driver/passenger and the perceived safety of the participants when traveling in their private vehicle.

A third manuscript has been submitted to Traffic Injury Prevention titled: The Effects of Obesity on Injury and Injury Risk to Occupants in Frontal Impacts. This manuscript is based on a doctoral thesis that has been completed. It formed the basis for another manuscript draft that describes the development and validation of a crash-simulation computational model using a surrogate wheelchair secured in a private vehicle environment by a docking-type securement device and with the occupant restrained by a vehicle-anchored lap/shoulder-belt restraint.

P3.1: July 2011 Project Update

The human-subject data-collection portion of the project was completed before 10/31/2009. Progress during this reporting period included the development of computer-simulation models representing a 50th percentile male occupant seated in a surrogate wheelchair secured by a docking-type securement device. The models are constructed using the MADYMO 3D crash-victim computational model and have been validated against sled-test data (see below). These models are being used to evaluate various belt-restraint configurations and to further study the interactions of drivers seated in wheelchairs with occupant restraints and vehicle interior components beyond results obtained from the sled impact tests described below.

To provide data for validating the computer model and to directly study the effects of restraint conditions observed during subject testing, sled tests have been conducted using different configurations of belt positioning on the midsize-male crash-test dummy. Belt configurations being studied include: 1) good belt fit achieved with open-front wheelchair armrests, 2) poor belt fit with the vehicle-anchored lap belt routed in front of closed-front armrests, 3) a shoulder belt with no lap belt, and 4) no seatbelts (i.e., an unbelted crash-test dummy). Sled-impact tests were also conducted with steering-wheelchair airbag deployments using two different deployment times, with a surrogate lap/shoulder belt, and with a vehicle-manufacturer's seatbelt equipped with a belt load limiter and seatbelt pretensioners. The results of these tests are also being used to investigate the risks of serious-to-fatal injuries from deploying airbags for drivers seated in wheelchairs, and to make recommendations on when it may be appropriate to deactivate the steering wheel airbag.

Three publications are currently being reviewed internally for inclusion in peer-reviewed journals. Two of the manuscripts focus on the survey results obtained from the 29 participants and the measurements taken of participants seated in their wheelchair ready for travel. These two papers will address qualitative and quantitative documentation of the issues and problems related to providing effective occupant crash protection for drivers and passengers in private vehicles who stay seated in their wheelchairs. They will also document the current status of seatbelt fit and usage, and will clarify the factors that prevent the use of properly positioned lap and shoulder belts on wheelchair-seated drivers. They also report on wheelchair securement systems and driver controls, their locations relative to the driver/passenger, and the perceived safety of the participants when traveling in their private vehicle. The third manuscript is based on a doctoral thesis and describes the development and validation of a crash-simulation computational model using a surrogate wheelchair secured in a private vehicle environment by a docking-type securement device, with the occupant restrained by a vehicle-anchored lap/shoulder-belt restraint.

P3.1: July 2010 Project Update

The human-subject data-collection portion of the project was completed before 10/31/2009. Progress during this reporting period included the development of a computer simulation model representing a 50th percentile male occupant seated in a surrogate wheelchair that is secured by a docking-type securement system. The model was constructed using MADYMO and validated against sled-test data. This model is currently being used to evaluate various occupant-restraint scenarios.

Three publications are currently being prepared for inclusion in peer-reviewed journals. Two of the manuscripts will focus on the survey results obtained from the 29 participants and the measurements taken of participants seated in their wheelchair ready for travel. These two papers will address qualitative and quantitative documentation of the issues and problems related to providing effective occupant protection for drivers and passengers in private vehicles who stay seated in their wheelchair. They will also document the current status of seat-belt fit and usage, and will clarify the factors that prevent the use of properly positioned lap and shoulder belts on wheelchair-seated drivers. They also report on wheelchair securement systems and driver controls, their locations relative to the driver/passenger and the perceived safety of the participants when traveling in their private vehicle. The third manuscript describes the development and validation of a crash-simulation computational model using a surrogate wheelchair secured in a private vehicle environment by a docking-type securement device and with the occupants restrained by a vehicle-anchored belt restraint system.

P3.1: July 2009 Project Update

A total 29 subjects were recruited, observed, and measured according to the test protocol. This includes collection of three-dimensional data describing occupant, wheelchair, vehicle-interior, and belt restraint geometry using a FARO arm 3-D digitizer for subjects tested at UMTRI. Summary reports for all subjects have been prepared and data from all subjects have been used to develop schematic drawings illustrating the geometry of subjects in their wheelchairs in relation to vehicle interior components and belt restraints. Results from this study, including subject responses to survey questions, in-vehicle measurements, and investigator observations have been used in three conference publications, including ISS 08, IASTED 08, and RESNA 08).

A computer model for simulating frontal-impact crash dynamics of wheelchair-seated occupants using a docking-type securement system has been developed using Madymo. The model has been validated from frontal-impact sled tests in which wheelchair accelerations, seat-belt loads, crash dummy kinematics, and docking securement forces were measured. The validated model is being used to evaluate prototype seatbelt configurations for wheelchair-seated drivers as well as to demonstrate the increased injury risk that results from the use of improperly positioned or incomplete use of lap/shoulder belt restraint systems.

A laboratory minivan buck has been modified for implementation of prototype restraint system designs that will be evaluated by wheelchair-seated drivers tested previously in their own vehicles.

Three publications are currently being prepared for inclusion in peer-reviewed journals. Two of the manuscripts will focus on the survey results obtained from the 29 participants and the measurements taken of participants seated in their wheelchair ready for travel. These two papers will address qualitative and quantitative documentation of the issues and problems related to providing effective occupant protection for drivers and passengers in private vehicles who stay seated in their wheelchair. They will also document the current status of seat-belt fit and usage, and will clarify the factors that prevent the use of properly positioned lap and shoulder belts on wheelchair-seated drivers. They also report on wheelchair securement systems and driver controls, their locations relative to the driver/passenger and the perceived safety of the participants when traveling in their private vehicle. The third manuscript describes the development and validation of a MADYMO model using the surrogate wheelchair secured in a private vehicle environment by a docking-type securement device and with the occupants restrained by a vehicle-anchored belt restraint system.

P3.1: July 2008 Project Update

A test protocol was developed, which includes forty questions and a checklist for observing and recording individuals while they enter and position themselves in their vehicles while seated in their wheelchair. A comprehensive measurement tool including illustrations was developed for use during the subject testing. A flyer was developed to recruit 25 or more subjects in the Pittsburgh and Southeast Michigan areas. Subjects were recruited from the Centers of Rehabilitation Services, the Center for Assistive Technology, Hiram G. Andrews Rehabilitation Center, and from local driver trainer organizations and vehicle modification programs.

A total 30 subjects were recruited, observed, and measured according to the test protocol. This includes collection of three-dimensional data describing occupant, wheelchair, vehicle-interior, and belt restraint geometry using a FARO arm 3-D digitizer for subjects tested at UMTRI. Case summaries for all subjects tested to date have wheelchair, vehicle-interior, and belt restraint geometry using a FARO arm 3-D digitizer for subjects tested at UMTRI. Case summaries for all subjects tested to date have been prepared and data from all subjects have been used to develop schematic drawings illustrating the geometry of subjects in their wheelchairs in relation to vehicle interior components and belt restraints.

A computer simulation model has been constructed from a wheelchair-seated individual using a docking type securement system. This model is currently being validated and will be used to evaluate various seat belt configurations in the vehicle interior.

In addition, the interior frame of a van is currently constructed to evaluate innovative passive restraint systems for use by wheelchair-seated drivers.

P3.1: July 2007 Project Update

A test protocol was developed, which includes forty questions and a checklist for observing and recording individuals while they enter, and position themselves in their vehicles while seated in their wheelchair. A comprehensive measurement tool including illustrations was developed for use during the subject testing. A flyer was developed to recruit 25 or more subjects in the Pittsburgh and Southeast Michigan areas. Subjects will be recruited from the Centers of Rehabilitation Services, the Center for Assistive Technology, Hyram G. Andrews Rehabilitation Center, and from local driver trainer organizations and vehicle modification programs.

IRB approval for the study has been obtained at Pittsburgh and is pending at the University of Michigan.

ADED and NMEDA have been targeted to obtain input from driver trainers as well as individuals that use their wheelchairs while driving/riding. These contacts have resulted in an invitation to present the issues of wheelchair-seated individuals in motor vehicles and to write an article in the ADED newsletter.

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Task P3.2: Development of WTORS for Improved Wheelchair User Restraint in Front and Rear Impacts of Private Vehicles

In Years 2 through 5 of this project, prototype devices and components that offer improved restraint effectiveness for front and rear impacts to wheelchair-seated drivers and passengers in private vehicles will be developed and evaluated in laboratory testing and in vehicle setups.  The focus of years 2 and 3 will be on occupant restraint systems for frontal crashes while the focus of years 4 and 5 will be on head and back supports for rear-impact protection.  As with the research effort of year 1, the primary focus will be on wheelchair-seated drivers, but passengers, particularly front-row passengers, will also be considered.

For improved frontal impact protection, the primary concerns are providing for improved fit of three-point belt restraints and allowing for increased use of frontal-impact airbags for wheelchair-seated drivers and right-front passengers.  Potential solutions that will be considered and explored include:

• Improvements in passive lap and shoulder belts that allow for easier and better fit to the driver or right-front passenger
• Modifications of powered wheelchairs to enable the easier and better fit of passive belt restraints
• Modifications to wheelchairs that provide for improved forward-moving and rearward-moving docking-type securement
• Improvements in wheelchair-integrated lap belts that provide for easier interface with a vehicle-anchored shoulder belt
• Refinements to prototype seatbelt buckles of vehicle-anchored lap belts
• Modification of vehicle hand controls to enable the use of frontal-impact airbags

For rear-impact protection, the primary concern is providing a properly positioned vehicle-anchored rear head restraint.  However, because most wheelchair backrests are not expected to provide effective back support in rear-impact loading, a vehicle-anchored back support must also be provided.  For drivers and front-row passengers, this will require a head-and-back restraint system that can be deployed after the occupant has moved into position, and removed when the occupant is ready to exit the vehicle, especially in emergency situations.  For example, a back and head support might be designed to automatically rotate up from the floor or down from the roof into contact with the wheelchair seatback in close proximity to the back of the user’s head after the driver’s wheelchair is secured in position. 

Along with the demonstration of a WTORS that provides enhanced protection in a rear-impact event, a draft WTORS standard will be developed that establishes test methods, design and performance criteria for these systems.  The standard will be harmonized with the other rear-impact standards and include a dynamic sled test at 16 mph and 8-10 g.  The design criteria will focus on the fit and proximity of the head/back support to the wheelchair user as well as its energy absorbing properties.  The performance criteria will focus on hardware integrity, allowed deflections, and control of the ATD movement.   The process of prototype development will enrich the standards process by demonstrating feasibility of meeting the criteria.

P3.2: July 2012 Project Update

During the past year, efforts were focused on several subtasks related to improving frontal-impact and rear-impact protection for drivers seated in wheelchairs. These include:

1. further development and evaluation of the seatbelt deployment system (SBDS),
2. continued collaborations with Q’Straint/Sure-Lok relative to commercialization of the Drive-In Occupant Restraint (DIOR),
3. crashworthiness evaluation of a commercially available deployable head/back restraint for rear-impact protection,
4. further investigation of interactions of drivers seated in wheelchairs with deploying steering-wheel airbags in frontal crashes using both sled-impact tests and simulations with a validated computational mode of a wheelchair-seated driver, and
5. further development of educational wheelchair-transportation-safety (WTS) materials targeted to stakeholder groups.
   

The SBDS is primarily targeted for use by drivers of personal vehicles seated in wheelchairs. The SBDS design has been improved through reduction in motor size, improved reliability of the floor anchorage locking mechanism, addition of control electonics that include safety features, and addition of operating controls. The development of a Drive-In Occupant Restraint (DIOR) system has been previously reported and is targeted for use by both drivers and passengers in different types of vehicles. This development project has been conducted in collaboration with Q’Straint/Sure-Lok, Inc. The DIOR has gone through several iterations in design and the latest version has been crash tested successfully and has been demonstrated at conferences and trade shows. It is now available for purchase from Q'Straint/Sure-Lok in the US and in Europe. Work is still being done to obtain patent protection on this invention.

We have also been successful in obtaining a sample of a commercially available deployable vehicle-anchored head/back restraint system for use by drivers seated in wheelchairs, and have conducted two 16-mph (delta V) rear-impact sled tests of the system using the surrogate wheelchair frame (SWCF) secured by the surrogate docking securement device (SDSD) described in last year’s report, and with a surrogate seating system installed. For these tests, the back support posts were attached to the SWCF using highly deformable elements so that the primary resistance to rearward movement of the crash-test dummy’s torso and head were provided by the head/back restraint system. However, although a front stabilizing bracket was used in both tests, the bracket on the SWCF came out of the retaining bracket mounted to the sled platform, which allowed the complete SWCF to rotate rear, resulting in increased loading on the head/back restraint system. Although the head/back restraint system provides some restraint during each test, we are working with the manufacturer to improve performance and will be conducting additional tests before the end of July 2012.

Interactions of drivers seated in wheelchairs with deploying steering-wheel airbags in frontal crashes were investigated further by conducting additional sled tests with both the midsize-male and small-female crash-test dummies and with various belt restraint conditions, including no seatbelts, poor seatbelt fit due to armrest interference, and good seatbelt fit with open-front armrests. The results of all these sled tests were used to further validate the MADYMO computer model of the wheelchair-seated driver and the validated model has been used to explore other conditions of driver/deploying-airbag interactions.

Response variables used in computer validations included accelerations of head, chest, and pelvis in X (forward) and Z (upward) directions, head injury criterion (HIC), neck forces, chest deflection, and left and right femur forces. The results from these tests and simulations indicate a potential risk for serious airbag-inflation-induced chest injury, especially for small-female drivers who are not properly restrained by a seatbelt (i.e., a loosely fitting belt restraint because of interference by wheelchair armrests) and who are sitting relatively close to the steering-wheel airbag module. However, there is also some concern for chest injuries to improperly belt-restrained average-size males and for neck injury to small females and unbelted midsize males for late-deployment airbag scenarios that can occur in offset-frontal crashes and with vehicle override. These results indicate the importance of providing good belt fit for drivers seated in wheelchairs to reduce the risk of serious chest injury from either airbag-deployment loading, poor belt fit, or both.

In a previous phase of this project, it was demonstrated that closed-front armrests significantly impede the proper fit of passive seatbelts on drivers seated in wheelchairs. Because most people who drive while seated in their wheelchair obtain their wheelchair before making a decision to drive and/or without consideration for seatbelt usage and fit, being able to retrofit wheelchairs that have closed-front armrest to having open-front armrest is critical to achieving good seatbelt fit, especially for drivers who required passive or nearly passive belt restraints. To investigate the feasibility and cost of making such armrest retrofits, the process of retrofitting the armrests on the wheelchair of one of the subjects who participated in the first part of this project was undertaken. The project team contacted the wheelchair manufacturer and the wheelchair prescriber to determine the particular style of open-front armrests that are compatible with the wheelchair model and the user’s needs. Upon completion of the armrest retrofitting, the driver returned to UMTRI to demonstrate the improved belt fit achieved with a vehicle lap/shoulder belt deployed by the SBDS. Because this particular individual liked to have his armrests positioned low on the wheelchair (i.e., below the tops of his thighs), and a joy stick support structure was located below the right armrest, the ability of the retrofit armrests to pivot upward also helped to provide proper positioning of the lap/shoulder belt deployed by the SBDS after the driver moved into position.

During the past year, a considerable effort has been placed on completing drafts of the DriveSafe brochure and several safety tip sheets aimed at wheelchair prescribers and van modifiers. Several different safety tip sheets for van modifiers are being developed according to the purpose for which the vehicle is being modified, including transportation mode (private versus paratransit), whether the client will be driving or riding as a passenger, and, if a passenger, whether the wheelchair will be secured by a docking device or a four-point, strap-type tiedown. Safety tip sheets for van modifiers are being divided into three parts. One part provides safety tips for the van modifier and their installer of tiedown/restraint equipment. The second part provides safety tips that the van modifier should communicate to the client and/or their caregiver prior to releasing the modified vehicle. The third part provides safety tips that the van modifier should give to the client for their future reference.

P3.2: July 2011 Project Update

During the past year, efforts were focused on several subtasks related to improving frontal-impact and rear-impact protection for drivers seated in wheelchairs. These include:

1. further development and evaluation of the forward-mount pivoting bar passive three-point belt restraint,
2. continued collaborations with Q'Straint/Sure-Lok relative to commercialization of the Drive-In Occupant Restraint (DIOR),
3. crashworthiness evaluation of a commercially available deployable head/back restraint for rear-impact protection,
4. completion of the design and fabrication of a surrogate wheelchair docking securement device for use in sled-impact testing of wheelchair-driver occupant protection systems,
5. investigation of the interactions of wheelchair-seated drivers with deploying steering-wheel airbags in frontal crashes using both sled-impact tests and simulations with a validated computational model,
6. preliminary computational investigations into the role of obesity in injury risk to occupants seated in wheelchairs, and
7. development of educational wheelchair-transportation-safety (WTS) materials targeted to stakeholder groups involved with wheelchair-seated drivers.

Further development and testing of the close-proximity knee restraint for frontal-impact protection of drivers seated in wheelchairs was discontinued. Upon further development and frontal-impact testing using prototype close proximity knee restraints installed on production minivan knee bolsters and driver instrument panels set up on the UMTRI impact sled, it was concluded that effective and acceptable implementation of this approach to providing lower-torso restraint for drivers seated in wheelchairs will be difficult and costly in different minivan vehicles. In addition, the peak femur forces in these frontal impact tests were higher than those predicted using computer simulations and were higher than would be considered acceptable.

Because the forward-mount pivoting bar system provides a way for drivers seated in wheelchairs to use the original vehicle-manufacturer's (i.e., OEM) driver three-point belt restraint in a nearly passive mode, the system has been renamed the Seatbelt Deployment Systems, or SBDS. Modifications made to the SBDS include:

• reducing the size of the gear-reduced DC motor that activates movement of the pivoting bar,
• adding a webbing-sensitive seatbelt retractor with buckle receptacle to the end of the pivoting bar and a seatbelt locking clip on the D-ring of the OEM seatbelt to keep the seatbelt buckle on the inboard side of the driver during storage, and
• modifying the floor anchorage locking mechanism so that it is completely recessed in the vehicle floor, thereby removing all interference and barriers to the driver maneuvering his/her wheelchair into and out of the driver space from/to a passenger-side entryway.

Further development and testing of a close-proximity knee restraint for frontal-impact protection of drivers seated in wheelchairs was discontinued. Upon further development and frontal-impact testing using prototype close-proximity knee restraints installed on production minivan knee bolsters and driver instrument panels set up on the UMTRI impact sled, it was concluded that effective and acceptable implementation of this approach to providing lower-torso restraint for drivers seated in wheelchairs will be difficult and costly in different minivan vehicles. In addition, the peak femur forces in these frontal impact tests were higher than those predicted using computer simulations and were higher than is considered acceptable.

Because the forward-mount pivoting bar system provides a way for drivers seated in wheelchairs to use the original vehicle-manufacturer's (i.e., OEM) driver three-point belt restraint in a nearly passive mode, the system has been renamed the Seatbelt Deployment System, or SBDS. Modifications made to the SBDS include:

• reducing the size of the gear-reduced DC motor that activates movement of the pivoting bar,
• adding a webbing-sensitive seatbelt retractor with buckle receptacle to the end of the pivoting bar and a seatbelt locking clip on the D-ring of the OEM seatbelt to keep the seatbelt buckle on the inboard side of the driver during storage, and
• modifying the floor anchorage locking mechanism so that it is completely recessed in the vehicle floor, thereby removing all interference and barriers to the driver maneuvering his/her wheelchair into and out of the driver space from/to a passenger-side entryway.

The improved version of the SBDS has been evaluated in several 30-mph frontal-impact sled tests using the surrogate wheelchair frame (SWCF) that was developed for independent evaluation of seating systems for use in motor vehicles. The SWCF was fitted with open-front armrests to achieve a good fit of the pelvic belt low on the pelvis of the midsize-male Hybrid III crash-test dummy. The SBDS performed extremely well in all tests with no hardware failures and with all crash-dummy peak forward and rearward movements well within the allowed excursion limits of SAE J2249 (soon to be WC18 of RESNA Wheelchair Standards Volume 4: Wheelchairs and Transportation), with one exception. The exception occurred when the SBDS was used with an OEM minivan driver seatbelt with emergency locking retractors (ELR) and shoulder-belt load limiter. Because of the load limiter, which limits the force applied on the occupant's chest in severe frontal crashes but allows higher excursions of the occupant's head, the head excursion of the ATD exceeded the excursion limit of SAE J2249/WC18. As noted below, this result indicates the importance of not deactivating the steering-wheel airbag for drivers seated in wheelchairs in late-model vehicles that are all equipped with load-limiting shoulder belts, for which the airbag is needed to prevent head/face injuries from impact with the steering wheel in moderate-to-severe frontal impacts.

An invention-report form has been filed with the University of Michigan Technology Transfer office for the Seatbelt Deployment System (SBDS). An industry partner is now being sought to pursue further development and commercialization of the SBDS.

In addition to the SBDS, which is primarily targeted for use by drivers of personal vehicles seated in wheelchairs, the development of a Drive-In Occupant Restraint (DIOR) system has been previously reported and is targeted for use by both drivers and passengers in different types of vehicles. This development project has been conducted in collaboration with Q'Straint, Inc (now Q'Straint/Sure-Lok, Inc.) Although the DIOR is not yet available for purchase, it has been through several iterations in design and the latest version has been successfully crash tested and has been on display at conferences and trade shows. It is therefore expected to be available for purchase within the next several months.

With regard to the commercially available deployable head/back restraint known as "Bakk Flip," we have continued our efforts to obtain samples of this product so that we can evaluate the system in both rear-impact and frontal-impact sled tests. While our efforts to obtain and test the head/back restraint samples have not yet been successful, we remain optimistic that samples can be obtained for testing in the near future.

To facilitate sled-impact testing conducted to evaluate restraint system performance by drivers seated in wheelchairs, the design of an EZ-Lock-type surrogate docking securement device (SDSD) was completed and validated by comparing load-cell measurement data from tests with the SDSD to comparable data from commercial docking securement systems. The new design allows for easy removal and replacement of a deformable retaining plate and has been used in several sled impact tests to evaluate the SBDS and to study the potential interactions of wheelchair drivers with deploying airbags as described below.

To investigate concerns about wheelchair driver interactions with deploying steering-wheel airbags in frontal crashes, several sled-impact tests have been conducted using late-model production minivan instrument panels, knee bolsters, and steering wheels equipped with airbag modules. Tests have been conducted for both early (10 ms) and late (40 ms) airbag deployment times typical of full-frontal and offset-frontal crashes, respectively. In these tests, several different configurations of OEM belt restraints have been used, including good belt fit provided by the SBDS with open-front armrests and poor restraint conditions observed in Task 3.1 testing, such as the lap-belt restraint routed in front of closed-front armrests with the buckle receptacle mounted to an inboard floor-mounted cable stalk. Also, one test was conducted without any belt restraints to examine a worst-case wheelchair-driver/deploying-airbag situation.

All tests were conducted using a midsize-male crash-test dummy positioned relative to the steering wheel and airbag module based on data collected in Task 3.1. The crash-test dummy was instrumented with head, chest, and pelvis accelerometers, chest-compression potentiometer, femur load cells, and both upper and lower-neck six-axis load cells. In no test, including the test with an unbelted crash-test dummy, was there any indication that the deploying airbag would have caused serious injuries to the chest or neck of the wheelchair occupant. These findings confirm that there is rarely a need to deactivate steering-wheel airbags for drivers seated in wheelchairs. Moreover, as noted above, OEM belt restraints in today's vehicles include belt load limiters that prevent excessive seatbelt loading on the occupant's chest but allow higher head excursions, thereby increasing the importance of having a steering-wheel airbag to prevent head/face injury from contact with the steering wheel.

The results of all these sled tests, including those to evaluate the SBDS and those to evaluate driver/airbag interactions, have been used to further validate the MADYMO computational model of a wheelchair-seated driver. This validated model is now being used to explore other conditions of driver/deploying-airbag interaction, including drivers involved in lower than 30-mph delta V frontal crashes and short-statured drivers who sit closer to the steering wheel and airbag module.

Research has also begun on studying occupant kinematics and injury risk during frontal impacts for obese wheelchair-seated occupants. Computer simulations of occupants with varying Body Mass Index (BMI) have been developed and validated. These models are being used to study the effects of obesity on seatbelt positioning and the risk of injuries to different body regions in frontal collisions.

Finally, during the past year, WTS educational materials specifically targeted to modifiers of personal vehicles and their clients have been under development. These include a Drive Safe brochure that is similar to the Ride Safe brochure but with the primary emphasis on outlining the steps to providing safe transportation for drivers seated in wheelchairs. These steps include obtaining a wheelchair that has been successfully crash tested for docking securement as well as a wheelchair with open-front armrests that allows for proper positioning of passive lap/shoulder belts when a driver moves his/her wheelchair forward into the driver space. In addition, the key stakeholder groups involved in the process of getting a patient fitted with a wheelchair and ready to drive from a personal vehicle have been identified and appropriate safety tip sheets targeted to these stakeholders are being developed.

P3.2: July 2010 Project Update

Efforts during past year have been focused on design, development, and evaluation of several restraint system concepts that will improve occupant protection for drivers and front-row passengers seated in wheelchairs in both frontal and rear impacts. For frontal impacts, these include:
1) the Drive-In-Occupant-Restraint (DIOR) in collaboration with a tiedown/restraint manufacturer,
2) the close-proximity knee restraint in combination with a shoulder belt and airbag, and
3) a new restraint concept called the forward-mount pivoting-bar passive three-point belt restraint.

Also, in the previous year, a Biomedical Engineering (BME) senior student design team developed and successfully crash tested a three-point belt restraint with wheelchair-anchored lap belt. The design was implemented and tested using an Invacare power wheelchair with the securement bolt moved rearward to reduce forward rotation of the wheelchair during frontal-impact loading, and with the lower wheelchair frame surrounding the securement bolt reinforced for anchorage of the lap belt and transmission of occupant restraint loads. The lap belt was threaded through supportive sleeves on each side to provide easy access by the wheelchair occupant, and modified airline-type buckles were used to facilitate connecting and disconnecting of the lap belt and attachment of the vehicle-anchored shoulder belt.

Evaluation of the design concepts for frontal crash protection has involved computer simulations using Madymo, evaluations by subjects from R5 (P3.1) testing using mockups of the design concepts in a laboratory minivan, and conducting frontal sled impact tests using a 30-mph, 20-g deceleration pulse. At this time, the forward-mount pivoting bar three-point belt restraint is the most promising for improving belt restraint fit, especially for drivers with wheelchairs that have armrests that are open at the front so as to allow the lap belt to move into contact with the lower pelvic region as the wheelchair driver moves forward into the driver station. The close proximity knee-restraint and the three-point belt with wheelchair-anchored lap belt would generally be used by people in wheelchairs that do not have open-at-the-front armrests.

As suggested by the discussion above, the type of armrest on a wheelchair plays a critical role in achieving good lap belt fit with vehicle-anchored passive belt restraints. For this reason, we have been investigating new concepts in wheelchair armrests designs and we have been communicating with wheelchair manufacturers with regard to optional designs in wheelchair armrests and the ability to retrofit wheelchairs that have closed-at-the-front armrests with open-at-the-front armrests. We have also been surveying subjects from R5 to obtain their input and opinions regarding armrest needs and preferences for different types of armrests. Responses from five subjects indicate that that open-at-the-front armrests would not pose any additional challenges for their daily routine as long as it is strong and sturdy enough for repeated weight bearing and is removable or movable to facilitate transfers.

We have also used data from the R5 (P3.1) testing to quantify the height of the armrest relative to the height of the top of the thigh to determine if there is sufficient clearance under the armrest for a pelvic belt to fit when the driver moves forward into position. Additional armrest designs that are being considered include an arc-shaped armrest support or an armrest support with belt guides that would be located below a cantilevered pivoting armrest surface. These supports would increase downward load bearing strength during transfers and mass shifting while allowing the belt restraints to move into proper positioning (over the armrest support but under the pivoting armrest surface) as the wheelchair driver moves forward into the driver station.

With regard to rear-impact protection, BME senior design students successfully crash tested their design for a deployable back/head restraint. Prior to sled testing, the restraint system was implemented in the minivan buck and evaluated by drivers from R5 testing. The primary negative response was that the linkage between the back/head restraint and the C-pillar blocks use of the driver-side sliding door.

We are also exploring the idea of a roof-mounted head/hack support that would move forward into position behind the wheelchair driver after he/she has moved into the driver station and that would move rearward along the roof when the driver is ready to exit the vehicle. In addition, during the NMEDA conference, contact was made with a Swedish manufacturer who has developed a deployable head/back restraint for people who drive from their wheelchair. The head/back restraint pivots on a vertical pole that is attached to the driver B-pillar. We are expecting to receive two of these units for rear-impact sled testing and evaluation in June.

In addition to developing and evaluating the different restraint system designs described above, we developed a surrogate docking securement station (SDSD) that replicates the wheelchair securement of typical commercial docking securement devices, such as EZ-Lock and QLock. The SDSD allows us to conduct sled tests to evaluate different restraint concepts without the need to use a different commercial docking securment device for each test. The design of the SDSD has been through several modifications to improve ease of use and to generate loads and wheelchair kinematics typical of those generated by commercial systems. The performance of the SDSD has been validated by comparing wheelchair kinematics and securement load histories measured by an array of four tri-axial load cells mounted between the SDSD or commercial securement device and the sled platform. The SDSD uses a low-cost replaceable and deformable steel plate with a thickness that achieves the desired forces and wheelchair kinematics.

During the past year, a total of 14 sled impact tests were conducted in support of the development and evaluation of new driver restraint systems. Two of these tests involved the close-proximity knee restraint and two were for the forward-mount pivoting-bar passive three-point belt restraint. Ten tests were conducted in developing, refining, and validating the surrogate docking securement station. Several tests were sponsored by a manufacturer to evaluate the crashworthiness of the DIOR system.

A non-provisional patent application was submitted by the University of Pittsburgh and Q'Straint on the DIOR system. Q'Straint has negotiated a license with the University of Pittsburgh to utilize the patent once it is granted.

P3.2: July 2009 Project Update

Results from the user observations of P3.1 have been compiled and evaluated. Two manuscripts of the research results are being prepared for submission this summer. Also as a result of the in-vehicle measurement of drivers and passengers, a Madymo computer simulation model was constructed and validated. An EZ-Lock type docking system model was developed with and without a front wheelchair stabilizer bar and the previously developed surrogate wheelchair model was added. Additional sled testing was conducted to measure docking system loads and overall kinetics and kinematics of the wheelchair and crash dummy during frontal-impact conditions. A series of crash tests conducted with/without the front stabilizer bar and with the pelvic belt anchored the sled platform (i.e., the vehicle floor) or the surrogate wheelchair. The model was validated based on the crash-test results and is being used to evaluate the potential effectiveness of prototype restraint systems and vehicle controls. A manuscript is currently being prepared that describes the development and validation of a wheelchair-seated driver Madymo model.

This task supporting the design of an improved restraint system for wheelchair-seated drivers by six students in a senior BME design course. The design involved a prototype wheelchair-anchored lap belt with modified buckle and interface to a vehicle-anchored shoulder belt, as well as modifications to a powered wheelchair to improve docking securement and provide effective lapbelt anchorages. A prototype of the restraint system with wheelchair modifications was successfully sled-impact tested using a simulated driver station.
In addition several conceptual designs were generated including a passive restraint design that has been made into a prototype. A provisional patent has been filed on this passive restraint for wheelchair seated drivers and a second prototype of this concept was developed by Q'Straint, a manufacturer of wheelchair tiedown and occupant restraint systems. Preliminary feedback on the concept was obtained from about ten wheelchair seated drivers and most feedback was positive.

In April 2008 a provisional patent was filed on this concept of a pivoting drive-in passive belt restraint system, which was converted in April 2009 to a joint patent application with Q’Straint and UPITT. Q’Straint is currently assisting in researching how this passive restraint device can be integrated with existing vehicle interiors.

Another development that came out of earlier brainstorming sessions is a knee-bolster concept and a head- and back-restraint to respectively prevent forward movement of a wheelchair-seated driver’s pelvis and rearward movement of the wheelchair and head and back of the occupant. UMTRI has acquired a minivan buck and has integrated both knee bolster concept and head-and back restraint so that feedback can be sought from wheelchair users.

P3.2: July 2008 Project Update

This task has been supporting the design of an improved restraint system for wheelchair-seated drivers by six students in a senior BME design course. The design involves the fabrication of a prototype wheelchair-anchored lap belt with modified buckle and interface to a vehicle-anchored shoulder belt, as well as modifications to a powered wheelchair to improve docking securement and provide effective lap-belt anchorages. A prototype of the restraint system with wheelchair modifications has been sled impact tested using a simulated driver station.

In addition several conceptual designs were generated including a passive restraint design that has been made into a prototype. A provisional patent has been filed on this passive restraint for wheelchair seated drivers and a second prototype of this concept was developed by Q'Straint, a manufacturer of wheelchair tiedown and occupant restraint systems. Preliminary feedback on the concept was obtained from about 10 wheelchair-seated drivers and feedback was positive. Q’Straint is currently assisting in
researching how this passive restraint device can be integrated with existing vehicle interiors.

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Last updated: 07.13.2012