Project P6: In-Depth Investigations of Motor-Vehicle Crashes and Moving-Vehicle Incidents Involving Passengers and Drivers Seated in Wheelchairs

Task Leader: Lawrence Schneider, PhD

Co-investigators: Kathleen Klinich, PhD, PE; Jamie Moore (senior crash investigator)

Other Participants: WTORS, wheelchair, and seating manufacturers; van modifiers, public and private transportation providers; wheelchair and seating suppliers and clinicians, other crash investigation programs, the NHTSA

Overview

This project addresses the key output of the RERC WTS by

• obtaining accurate and objective knowledge of the transportation experience by wheelchair users,
• including vehicle ingress/egress,
• wheelchair securement,
• occupant restraint, and
• injury causation scenarios.

It does this through the conduct of in-depth investigations of crashes or other moving-vehicle incidents involving passengers and drivers seated in wheelchairs to identify the types and causes of injuries. 

View these PDF documents to learn more how you can participate in this important study: Cover Letter Study Description Recruitment Poster

This project is a continuation of a crash-investigation program funded by the first RERC on Wheelchair Transportation Safety, and will take place over the 5 years of the project.  The project will result in objective assessments and documentation of injuries and injury causation scenarios for passengers and drivers involved in adverse incidents and crashes while seated in their wheelchairs in different types of private and public vehicle and transportation environments.  This information is needed to guide future R&D and standard-development efforts, and will be used to educate key stakeholders.

Expected Outputs and Short-Term Outcomes

Expected Outputs

• Peer-reviewed publications documenting causation injury scenarios to occupants seated in wheelchairs while traveling in minvans, vans, and paratransit buses
• Identification of issues with WTORS and wheelchair designs that prevent optimal protection of wheelchair-seated occupants
• Recommendations for improved training and education based on the most frequent misuses of WTORS by wheelchair-seated occupants

Expected Outcome (Short and Intermediate Term)

• Improvements in wheelchair occupant safety in private vehicles

Research Objectives

The goal of this project to build on the accomplishments of the previous RERC by continuing to conduct in-depth investigations of crashes and other moving-vehicle adverse incidents that have the potential to result in injuries to drivers and passengers seated in wheelchairs while traveling in different types of motor vehicles.  Through biomechanical analysis of individual cases and statistical analysis of a new crash/injury database, this project will:

• Identify areas and issues of motor-vehicle injuries that may be unique to wheelchair-seated occupants in different types and sizes of vehicles and transportation services,
• Document injury scenarios involving use of inappropriate procedures (e.g. side facing) and tiedown/restraint and wheelchair equipment that does not comply with current voluntary standards,
• Evaluate the performance wheelchair and WTORS that comply with current standards and recommended practices, and
• Characterize, in relation the able-bodied population, the extent, incidence, and nature of injuries to wheelchair-seated occupants in different types and sizes of vehicles.

Project Update

P6: July 2012 Project Update

During the past year, 11 notifications of crash and non-crash events involving occupants seated in wheelchairs were received and five of these qualified for investigation and inclusion in the UMTRI wheelchair-occupant crash/injury database. This database now contains data on a total of 62 cases of crash and non-crash events involving occupants seated in wheelchairs.

Analysis of the UMTRI wheelchair/crash injury database has been conducted to explore injury risk factors for occupants seated in wheelchairs in frontal crashes. The methods and results are being documented in a manuscript that will be submitted to a peer-reviewed journal.

For this analysis, cases were restricted to the 39 wheelchair occupants involved in frontal crashes because there were insufficient numbers of cases in other crash modes (side, rear, rollover) to allow consideration of crash type as an injury predictor. To conduct logistic regression analysis, injury outcome was classified as acceptable outcome (no injury, minor injury, or moderate injury – i.e, Abbreviated Injury Scale (AIS) < 2) or adverse outcome (serious to fatal injury – i.e., AIS > 3) (Baker et al. 1974). Factors considered as potential predictors of outcome included crash severity, wheelchair tiedown type (4-point strap system or docking securement device), tiedown usage (proper, improper, none), occupant belt-restraint condition (optimal, suboptimal, none), seating position (front versus rear rows), vehicle type (minivan, van, small bus, large bus), occupant age, and occupant gender.

Proper belt restraint was considered to be the use of a lap/shoulder belt without “known” misuse or improper positioning of the belts on the occupant, with or without airbag deployment. However proper belt restraint cannot be known with certainty and this is especially true for people seated in wheelchairs for which wheelchair components, such as armrests, often interfere with good belt positioning, and especially with the lap belt positioned low on the pelvis. Suboptimal belt restraint included using only a lap belt, using only a shoulder belt, an airbag deployment without using seatbelts, and any type of belt restraint with documented misuse, such as positioning the lap belt over armrests at the level of the abdomen or in front of the armrests and therefore away from the occupant. The use of only a wheelchair-mounted postural belt was classified as unrestrained because postural belts are not designed and tested to provide protection in a crash.

To allow analysis of factors contributing to injury for the general population compared to the population of occupants seated in wheelchairs, injury analysis was also performed on a subset of data from the NASS-CDS database. Frontal crashes from 2000 through 2010 where the occupant was traveling in a minivan, van, SUV, small bus, or large bus were included, where large buses are only included when they are involved in a crash with a smaller vehicle. Occupant age was restricted to 8 years and older, which corresponds to the same age range in the wheelchair occupant dataset, as well as the population where vehicle lap/shoulder belts might be expected to offer reasonable protection without the use of a child safety seat or belt-positioning booster seat.

Multivariate logistic regression was performed on each dataset to identify significant predictors of injury. Odds ratios of factors contributing to injury risk were calculated. Estimates of injury risk were not calculated for the wheelchair-occupant dataset because the crashes do not represent a random distribution of crashes. However, this dataset can still be used to identify odds ratios of factors contributing to injury (Breslow, 1996).

Results from these analyses indicate that seatbelts are less effective and that occupant age has a more significant effect on injury risk for occupants seated in wheelchairs compared to occupants who are using the vehicle manufacturer’s seats and seatbelts. The reduced seatbelt effectiveness for occupants in wheelchairs may be due, in part, to improper placement of seatbelts that were classified as properly positioned, due to interference by wheelchair components and/or a lack of caregiver/driver training on how to properly position seatbelts on occupants seated in different types and models of wheelchairs. It is also hypothesized that even properly positioned seatbelts may not be as effective in reducing the risk of serious injuries to occupants in wheelchairs as they are for other vehicle occupants because of a lower injury tolerance. However, it can also be expected that the relatively small sample of frontal crashes in the UMTRI wheelchair-occupant crash/injury database effects these results.


References

• Baker SP, O’Neill B, Waddon W Jr, Long WB. The Injury Severity Score: a method for describing patients with multiple injuries and evaluating care systems Journal of Trauma 1974;14:186-7.
• Breslow, NE. Statistics in Epidemiology: The Case-Control Study Journal of American Statistical Association 1996 91(433):14-28.

P6: July 2011 Project Update

Unfortunately, many notifications do not result in a case that can be investigated and included in our database. There are several reasons for this, including the inability to obtain information to contact the occupant who was seated in a wheelchair or their caregiver, and the unwillingness of the wheelchair occupant or their caregiver to participate in the study.

However, even when a notification does not result in the ability to complete a full investigation, the information obtained from the notification is often of value. For example, it is often reported that a person in wheelchair tipped over due to lack of complete and effective wheelchair securement. In this regard, our findings from this project continue to point to the high risk of serious-to-fatal injuries for people riding in vehicles while seated in wheelchairs during relatively minor crash events and in non-crash events such as vehicle turning and stopping. This high risk of injury is due to both the lack of effective wheelchair securement as well as the non use or improper use and/or positioning of belt restraints.

P6: July 2010 Project Update

The original IRB application was submitted to the University of Michigan Social and Behavioral Institutional Review Board (IRB) and approval was received in February 2007. The project received continued approval in May 2009 and again in February 2010. Arrangements made with the NHTSA to obtain notifications of crashes involving a wheelchair-seated occupant from the National Automotive Sampling System (NASS) have been very productive. Since the beginning of the current funding cycle, reports on 31 new cases have been completed and added to the wheelchair crash/injury database.

P6: July 2009 Project Update

The original IRB application was submitted to the University of Michigan Social and Behavioral Institutional Review Board (IRB) and approval was received in February 2007. The project received continued approval in May 2009. Arrangements made with the NHTSA to obtain wheelchair notifications from the NASS have been very productive. Since the beginning of the current funding cycle, reports on 23 new cases have completed and added to the wheelchair crash/injury database.

P6: July 2008 Project Update

The IRB application was submitted to the University of Michigan Social and Behavioral Institutional Review Board (IRB) and approval was received in February 2007. The project received continued approval in February 2008. Minors are now eligible for inclusion in the study although children under 12 will not participate in phone interviews. The methods of recruitment have been expanded and arrangements have been made with the NHTSA to obtain wheelchair notifications from the NASS. This effort, along with additional funding from the National Highway Safety Administration, has resulted in a steady pace of crash notifications and the potential to double the proposed number of cases that will be investigated in the study. To date, a total of 14 new cases have been identified for inclusion in the database.

P6: July 2007 Project Update

The IRB application was submitted to the University of Michigan Social and Behavioral Institutional Review Board (IRB) and approval was received in February 2007. Minors are now eligible for inclusion in the study although children under 12 will not participate in phone interviews. The methods of recruitment have been expanded and arrangements are being made with the NHTSA to obtain wheelchair notifications from the NASS beginning in July 2007.

In the first six months of the project, five new crashes involving occupants seated in wheelchairs were identified and three of these resulted in full investigations. The first case involves a wheelchair-seated driver of van in a frontal impact who sustained serious lower-extremity injuries. Because the vehicle had already been repaired at the time of the notification, photo documentation of the vehicle damage being supplied by the occupants is needed to complete the investigation. The second notification was from the CIREN center at the Children’s Hospital of Philadelphia (CHOP) and involved a wheelchair-seated driver in an offset-frontal impact who sustained serious abdomen and lower extremity injuries. Finalization of the CIREN case review is needed before we can complete our investigation. The third notification was from Google News Alerts and involved a modified vehicle but the wheelchair-seated occupant was not present during the crash so a full investigation was not conducted. The fourth notification involved a rear endswipe of a vehicle with a 6YO child seated in a wheelchair who was not seriously injured. This investigation has been completed. A fifth notification was identified through local news reports and involved a vehicle with a wheelchair-seated occupant becoming airborne and landing on a large rock. The wheelchair user in this collision declined to participate in the study.

P6 Annual Report 2007 (512K pdf)

Last updated: 07.18.2012