SP-2b: Biomechanics of Injury to Wheelchair-Seated Occupants in Side Impacts

Task co-leaders: Lawrence Schneider, PhD and Miriam Manary, MSE

Co-investigator: Gina Bertocci, PhD

Other participants: University of Michigan Engineering Graduate Student (student), Jean Marc Girardin of Q’Straint (manufacturer), Ruth Lytle of Everest and Jennings (manufacturer), Steve Linquist of Sunrise Medical Mobility Systems (manufacturer), Jim Swinehart of Metalcraft Industries (manufacturer), Tom Novotny of AES (manufacturer), University of Michigan Health System Physical Therapists and Patients (clinicians and consumers), and RESNA SOWHAT members (researchers, clinicians, consumers, students, and industry representatives).

Duration/Staging of task: This is a 30-month research task that will be conducted primarily in months 31-60 of the 60 month RERC cycle.


Progress Report May 1, 2005 | Progress Report May 1, 2006
5 year report  June 1, 2006


Research objectives

This Task is based on the hypothesis that side-impact protection can be significantly improved for wheelchair-seat travelers, particularly for far-side impact scenarios, by understanding and applying the established concepts and test methods of side-impact protection developed for the automotive environment. A primary objective is to investigate and report on safety issues related to the biomechanics of injury in side impacts, particularly as they apply to wheelchair-seated travelers. However, it is also planned to develop design and performance criteria, and associated test methods, that will improve wheelchair-user safety in side impacts, and to work with collaborating wheelchair and WTORS companies to improve side-impact performance of products. The results of this effort will increase the understanding of the problem of side-impact protection for wheelchair users and will benefit wheelchair travelers by improving their level of crashworthiness safety in motor vehicles.

The research and development plan is similar to that proposed in SP2a for rear-impacts, and involves several sub tasks with individual objectives. These include:

  1. conduct a thorough review of the biomechanical literature and existing federal safety standards relevant to side-impact crashes, and summarize and document the results as they may be relevant to developing test methods, and design and performance requirements for devices and equipment used by wheelchair-seated occupants.
  2. using input from Task 1c to determine an appropriate impact pulse, conduct simulated side-end impact tests to evaluate the performance of different types of wheelchairs and WTORS that comply with the frontal crash requirements of SAE J2249 and ANSI/RESNA WC/19 to assess the problem areas and needs.
  3. based on the results of (b), develop appropriate modifications to test methods and test instrumentation for conducting side-impact sled tests.
  4. modify existing computer models used for frontal-impact wheelchair/occupant simulations for use in side-impact simulations, and validate models using results from sled impact tests conducted in (b) and (c),
  5. use sled impact testing and computer simulations to study far-side impact protection issues for wheelchair-seated occupants and to establish performance criteria for wheelchairs and wheelchair components, such as armrest,
  6. use the results from (a) through (e) to establish a set of test methodologies and associated performance criteria for inclusion in future wheelchair and WTORS standards related to side-impact protection,
  7. in conjunction with collaborating manufacturers, develop prototype securement systems and wheelchair components that improve side-impact performance relative to criteria established in (f).

Anticipated outcomes

The overall goal of this activity is to reduce rear-impact injury for people who travel in a motor vehicle while seated in a wheelchair. This task will result in:

  1. a thorough compilation and analysis of existing literature on rear impact,
  2. an impact pulse appropriate for rear impact testing and simulation,
  3. an evaluation of current wheelchair and wheelchair tiedown designs as to their appropriateness for rear-impact protection,
  4. new test methods and instrumentation requirements for assessment of rear-impact risks
  5. new computer models that simulate rear-impacts of wheelchair–seated travelers,
  6. an understanding of the geometric constraints and challenges of providing vehicle –mounted head and back support systems,
  7. rear impact performance criteria and draft standards, and prototype hardware and/or design requirements that can aid manufacturers in the creation of products with improved rear-impact protection.

References

Blaisdell, D., Stephens, G., and Meissner, U., Collision Performance of the Automotive Door Systems. Paper 940562, SAE, Warrendale, PA, 1994.

Cavanaugh, J.M., Zhu, Y., Huang, Y., and King, A.I., Injury and Response of the Thorax in Side Impact Cadaveric Tests. Proceeding of the 37th Stapp Car Crash Conference, Paper 933127, SAE, Warrendale, PA, 1993.

Cavanaugh, J.M., Huang, Y., Zhu, Y., and King, A.I., Regional Tolerance of the Shoulder, Thorax, Abdomen, and Pelvis to Padding in Side Impact. Paper 930435, SAE, Warrendale, PA, 1993.

Cesari D., and Bloch, J., The Influence of Car Structural Behaviour on Occupant Protection in Car-to-Car Side Impact. International Conference on Vehicle Structures, C163/84, pp 7-10, Mechanical Engineering Publications Limited, London, England, 1984.

Dalmotas, D.J., Injury Mechanisms to Occupant Restrained by Three-point Seat Belts in Side Impacts. Paper 830462, SAE Warrendale, PA, 1983.

Daniel, R.P, Biomechanical Design Considerations For Side Impact. Paper 890386, SAE Warrendale, PA, 1989.

Eppinger, R.H., Marcus, J.H., and Morgan M.M., Development of Dummy and Injury Index for NHTSA’s Thoracic Side Impact Protection Research Program. Proceedings of the 28th Stapp Car Crash Conference, Paper 840885, SAE Warrendale, PA, 1984.

Fildes, B., Vulcan, P., and Lane, J., Side Impact Crashes in Austrailia, Proceedings of the 14th ESV conference, NHTSA, Washington, DC, 1994.

Gloyns, P., and Rattenbury, S. Fatally Injured Struck Side Occupants in Side Impacts. TRRL Contractors Report 113, 1989.

Häland, Y., Lövsund, P, and Nygren, A, Life-Threatening and Disabling Injuries in Car-to-Car Side Impacts – Implications for Development of Protective Systems. Accident Analysis and Prevention, Vol 25, pp. 199-205, 1993.

Huang Y., King, A.I., and Cavanaugh, J.M. A MADYMO Model of Near-side Human Occupants in Side Impact, Journal of Biomechanical Engineering, Vol. 116, May 1994.

Plank, G.R., and Eppinger, R.H., Computed Dynamic Response of the Human From a Finite Element Model. Proceedings of the 12th ESV Conference, NHTSA, Washington, DC, 1989.

Tarriere, C., Walfisch, G., and Fayon, A., Synthesis of Human Tolerance Obtained From Lateral Impact Simulation. Proceedings of the 7th ESV Conference, pp. 359-373, NHTSA, Washington, DC, 1979.

Thomas, P., and Bradford, M., Side Impact Regulations, How Do They Relate to Real World Accidents?, Proceedings of the 12th ESV Conference, NHTSA, Washington, DC, 1989.

Viano, D.C., Lau, I.V., Cordin A., King, A.I., and Begeman, P., Biomechanics of Human Chest, Abdomen and Pelvis in Lateral Impact, Accident Analysis and Prevention, Vol 21, pp. 553-574, 1989.

Viano, D.C., Evaluation of Armrest Loading in Side Impacts. Proceedings of the 35th Stapp Car Crash Conference, Paper 912899, SAE, Warrendale, PA, 1991.

Wang, J.T., Analytical Studies of Injury Criteria for the Thorax. Journal of Biomechanical Engineering, Vol. 1, 1989.

Warner, C.Y, Strother, C.E., James, M.B., Struble, D.E. and Egbert, T.P., Crash Protection in Near-side Impact – Advantages of a Supplemental Inflatable Restraint. Technical paper 890602, SAE, Warrendale, PA, 1989.

Warner, C.Y, James, M.B., Strother, C.E. A perspective on side impact occupant crash protection . Technical paper 900373, SAE, Warrendale, PA, 1990


Progress Report May 1, 2005

This task focuses on occupant protection for forward-facing, wheelchair-seated drivers and passengers in lateral impacts to the side of the vehicle opposite to where the occupant is seated. The project activities include: 1) evaluating how wheelchairs and WTORS that comply with current voluntary crashworthiness standards perform under far-side impact conditions, 2) reviewing and synthesizing the relevant side impact and biomechanical literature, 3) developing a test method for evaluating wheelchair and WTORS performance far-side impact loading, 4) determining associated response parameters and performance criteria for the test method of (3), and 5) developing and implementing improvements in wheelchair and WTORS designs that reduce the risk of wheelchair user injury in far-side impacts . The work this year has focused on items 1 through 4.

 

Six side-facing sled tests of commercial wheelchairs and WTORS were conducted to determine how products that comply with current frontal crash test requirements perform in a far-side impact crash. The crash severity simulated was between 14-18 mph delta V with 14-g deceleration, and all tests used a mid-size male crash test dummy. Test results indicate the effects of different wheelchair mass, different types of WTORS including four-point tiedown and docking securement, fabric and planar seating, and different shoulder-belt geometries on wheelchair and dummy lateral excursions.

 

The results of these and future tests, along with information from the literature, will be used to establish design specifications and performance criteria for wheelchairs and WTORS that will improved protection for forward-facing wheelchair users in far-side impacts. These specifications and criteria, and the associated test methods, will be implemented in additional wheelchair and WTORS standards.


Progress Report May 1, 2006

This task is focused on occupant protection for forward-facing, wheelchair-seated drivers and passengers in impacts to the side of the vehicle opposite to where the occupant is seated, which are often referred to as far-side impacts. The project activities include:

  1. an evaluation on how wheelchairs and WTORS that comply with current voluntary crashworthiness standards perform in far-side impact conditions,
  2. a review of the relevant literature,
  3. development of a test method for evaluating wheelchair and WTORS performance far-side impact loading,
  4. determination of response parameters and performance criteria for the test method of (3), and
  5. identifying features of wheelchair and WTORS that will reduce the risk of wheelchair user injury in far-side impacts.

In the previous year, six side-impact sled tests of commercial wheelchairs and WTORS were conducted to determine how products that comply with current frontal crash test requirements perform in a far-side impact crash. The crash severity simulated was between 14 and 18 mph delta V with 14-g average deceleration, and all tests used an instrumented mid-size male Hybrid III crash test dummy. Test results indicate the effects of wheelchair mass, use of four-point tiedown versus docking securement, fabric versus planar seating systems, and different shoulder-belt geometries on wheelchair and dummy lateral excursions. The test series showed that current wheelchair designs and wheelchair securement methods perform well in far side impact but that quality occupant restraint and containment to the seating area were lacking. This is particularly concerning because the literature suggests that most injuries in far-side impact are due to excessive lateral occupant excursion leading to contact with the vehicle interior or other occupants. In the current year, insights from this initial test series led to a second test series that further the effects of lap-belt anchor point location (either to the wheelchair or to the vehicle floor) and seat system characteristics (fabric versus planar seating) on lateral excursions of the ATD using the surrogate wheelchair base as a generic platform for testing. The tests indicate that use of fabric seating and wheelchairanchored lap belts reduce peak lateral head excursions, and thereby reduce the risk of injury in far-side impacts.

Additional tests are being conducted to explore the benefits or disbenefits of other seating features, such as lateral-torso postural supports, to injury risk in far-side impacts. The results of these studies, along with information from the literature, will be used to establish design guidelines and test methods for wheelchairs and WTORS that will improve protection for forward-facing wheelchair users in far-side impacts. These specifications and criteria, and the associated test methods, will be implemented, as appropriate, in wheelchair and WTORS standards.


5 year report  June 1, 2006

This task is focused on occupant protection for forward-facing, wheelchair-seated drivers and passengers in impacts to the side of the vehicle opposite to where the occupant is seated, which are often referred to as far-side impacts. The project activities include: 1) an evaluation on how wheelchairs and WTORS that comply with current voluntary crashworthiness standards perform in far-side impact conditions, 2) a review of the relevant literature, 3) development of a test method for evaluating wheelchair and WTORS performance far-side impact loading, 4) determination of response parameters and performance criteria for the test method of (3), and 5) identifying features of wheelchair and WTORS that will reduce the risk of wheelchair user injury in far-side impacts.

Six side-impact sled tests of commercial wheelchairs and WTORS were conducted to determine how products that comply with current frontal crash test requirements perform in a far-side impact crash.  The crash severity simulated was between 14 and 18 mph delta V with 14-g average deceleration, and all tests used an instrumented mid-size male Hybrid III crash test dummy.  Test results indicate the effects of wheelchair mass, use of four-point tiedown versus docking securement, fabric versus planar seating systems, and different shoulder-belt geometries on wheelchair and dummy lateral excursions.    The test series showed that current wheelchair designs and wheelchair securement methods perform well in far side impact but that quality occupant restraint and containment to the seating area were lacking.   This is particularly concerning because the literature suggests that most injuries in far-side impact are due to excessive lateral occupant excursuion leading to contact with the vehicle interior or other occupants.

The insights from this initial test series led to a second test series that further the effects of lap-belt anchor point location (either to the wheelchair or to the vehicle floor) and seat system characteristics (fabric versus planar seating) on lateral excursions of the ATD using the surrogate wheelchair base as a generic platform for testing.  The tests indicate that use of fabric seating and wheelchair-anchored lap belts reduce peak lateral head excursions, and thereby reduce the risk of injury in far-side impacts.    Additional tests are being conducted to explore the benefits or disbenefits of other seating features, such as lateral-torso postural supports, to injury risk in far-side impacts.

The results of these studies, along with information from the literature, will be used to establish design guidelines and test methods for wheelchairs and WTORS that will improve protection for forward-facing wheelchair users in far-side impacts. These specifications and criteria, and the associated test methods, will be implemented, as appropriate, in wheelchair and WTORS standards.

Last updated: August 18, 2006

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