SP-3b: Development and Evaluation of Docking Devices for Use in Low g Environments

Task leader: Douglas Hobson, Ph.D. (rehabilitation engineer)

Co-investigators: Linda van Roosmalen, Ph.D. (industrial designer/ rehabilitation scientist); Lawrence W. Schneider, Ph.D. (transportation safety specialist); Paul Dick (primary user/ Advisory Board member.

Other advisory participants: Lucy Spruill (primary user); Joe Tackas, Kinedyne Corp. (securement manufacturer); Doug Cross (public transporter/ Advisory Board member); TBD (bus manufacturer); Jean Marc Girardin, Q-Straint (securement manufacturer)

Duration/Staging of task: This 24 month development task will be conducted in months 25-48 of the 60-month RERC cycle.

Importance of the problem

Description of the need, target population and state-of-the-art

Task SP-3a will focus on investigations related directly to the support of the universal docking interface geometry (UDIG). The UDIG standard is predicated on the fundamental concept that docking systems that comply with the UDIG will accommodate both high-g and low-g crash situations. This is clearly a logical first step given that all current strap-type systems must meet the high-g requirement, and marketing lower-g securement devices, to date, has not been supported by securement manufacturers. However, designing all docking securement systems to meet a high-g strength requirement ignores the potential of developing a low-g standard and securement options for use in situations in which, statistically and physically, high-g crash loads are very unlikely to occur. It also ignores what is actually happening in other western countries. Finally, if viable securement system(s) could be developed and shown to be effective for use in low-g transport environments, they would not necessarily be dependent on the adoption and implementation of the UDIG standard before their implementation in the transport marketplace.

A case can be made, which will hopefully be further strengthened by the findings of Task SP-1c, that transport situations exist, mainly involving large transit vehicles, in which statistically it is highly unlikely that a WMD rider will experience a crash event (Shaw, 2000). Furthermore, it can be argued that it is much more likely that a WMD rider may experience events associated with emergency driving, such as in the case of maximum braking or swerving to avoid an accident. Reger and Adams have shown that emergency driving maneuvers typically occur at deceleration or acceleration levels less than 1g (Reger and Adams, 1994). In response to these findings, the SAE Restraints Task Group (SAE, 1996), and more recently the ANSI/RESNA SOWHAT committee, have recommended the development of a low-g standard as a priority future work item.

European countries (England, Germany and France) and Canada are now implementing rearward-facing WMD compartments in large transit buses with only passive WMD securement. Although this approach is in opposition to the literal interpretation of ADA (Architectural and Transportation Barriers Compliance Board, 1991), it is clearly a trend that if it can be improved upon and shown to be safe, would offer significant convenience over current strap-type securement devices (in low-g environments). However, the current passive system will not adequately secure most WMDs under emergency driving conditions, or when the vehicle ascends a hill with a slope in excess of about 10° (Hobson and Bertocci, 1997).

In 1996-97, the task leader served as a consultant to Delcan Ltd., a private consulting group to the Ontario Ministry of Transport. The focus was to weigh the options for safe wheelchair securement in new low floor buses. Reward facing passive restraint was one of the options being seriously considered, and now implemented in several Ontario municipalities. Recommendations to Delcan Ltd. from the task leader, listing potential safety problems with passive securement, were contained in a private consultant report (Hobson and Bertocci, 1997). In the same study program, Rutenberg presented the results of his survey of western European transport systems, several of which had already ventured down the path of passive securement, with Germany leading the way (Rutenberg Design Inc.,1997).

The primary target constituency for alternate low-g securement is the WMD user seeking independent access to large public transit vehicles, and the public transit authorities. There are no known devices in the marketplace designed to supplement the passive approach in order to resolve the problems indicated above.

Beneficial impact on target constituency, including service providers

The primary advantage to WMD users is the potential independence offered by a simplified strap-less low-g securement system. For transit operators it could eliminate or substantially reduce the frequency of which the operator must leave the driver’s station. And finally, it would reduce the time required for ingress and egress of the WMD user, and thereby some of the stigma associated with a source of transit delays.


To design, develop, test and evaluate a series of low-g and ultra-low-g securement concepts and devices that have the potential to enhance independent access of WMD users to public transit vehicles.


  1. Formalize the membership of the collaborative investigative team, consolidate industry and consultant partnerships, share information with volunteer participants, prioritize development objectives, confirm user/engineering specifications
  2. Conceptualize low-g designs incorporating engineering and user/transporter specifications arising from SP-1c findings and standards deliberations
  3. Design, develop and test laboratory prototype designs
  4. Subject designs to constituency validation testing
  5. Refine designs and foster transfer to commercial availability.


Architectural and Transportation Barriers Compliance Board (1991). Americans with Disabilities Act (ADA) Accessibility Guidelines for Transportation Vehicles.

Hobson, D.A. & Bertocci, G.E. (1997). Overview of Trends in Personal Mobility Devices and Related Securement Technology - A Final Report. Delcan.

Krouskop, T. (1992). Wheelchair Restraint System. Houston, TX, NTIS.

Reger, S. and Adams, T. (1994). Transit Restraint System for Wheelchair Users.

Rutenberg Design Inc. (1997). MTO low floor bus study - Technical Memorandum.

SAE (1996). Wheelchair tiedowns and occupant restraints (WTORS) for use in motor vehicles.

Shaw, G. (2000). “Wheelchair Rider Risk in Motor Vehicles.” Journal of Rehabilitation Research & Development 37(1): 89-100.

Progress Report May 1, 2004


Task 3b officially began Nov.1, 2003. The task priorities and title were revised slightly to reflect changes and current needs in the US transportation industry. The task is now placing initial emphasis on the support of standards development for low g transit vehicle environments.

Progress Report:

A draft standard has been prepared and presented to the ISO WG-6 in March, 04 for consideration as a new work item. A similar presentation will be made in June 04 to the ANSI/RESNA Standards Committee on Wheelchair Transportation. R&D work in support of these standards will commence once the direction the standards will take has been confirmed.

Progress Report May 1, 2005

Technology for use in low g transport environments a. Leadership for two revisions of the preliminary work item (PWI) working draft (WD) on Rear-facing wheelchair passenger spaces in large accessible transport vehicles (RF-WPS) in preparation for national body voting as a new work item (NWI) for ISO-working group 6 (WG-6) b. Design and initiation of a data base of wheelchair measures to guide decision-making of the design requirements for the RF-WPS c. Review and compilation of the research findings on 'g' forces incurred during emergency driving conditions in large transit vehicles. Results to be used to guide test method development. d. RF-WPS distributed to participation national bodies for voting on acceptance as NWI for WG-6. e. Conducted second meeting of ANSI/RESNA break-out group on RF-WPS in an ongoing effort to develop a knowledgeable stakeholder group that will guide the effort towards an ultimate US national standard on RF-WPS that reflects the needs of the US transit marketplace.

Progress Report May 1, 2006

Working drawings of the third design iteration were completed and the prototype is under construction. Provisional patent with commercial partner is in final stages of preparation. Second draft of industry consensus document on changes to ADA was distributed to RESNA standards working group for feedback. Contacts were made with APTA and the Access Board. RERC comments submitted in response to DOT-NPRM announcement on changes to ADA. ISO standard on Rear-facing Wheelchairs Passenger Stations has been advanced and development and testing of the surrogate test wheelchair is in process.

 Last updated: August 18, 2006