SP-3a: Development of Tech in Support of Universal Docking Interface Geometry (UDIG) Securement Standard

Task leader: Douglas A. 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)

Other participants: Lucy Spruill (primary user); Joe Takacs (securement manufacturer); Doug Cross (public transporter); ISO-WG6 and ANSI/RESNA SOWHAT standards groups and members; Jean Marc Girardin, Q'Straint (securement manufacturer)

Duration/Staging of task: This 24 month development task will be conducted in months 0-24 of the 60 month RERC cycle.

Importance of the problem

Description of the need and target population

In addition to the overall needs statement presented in the Introduction section, several additional importance/need statements can be made specific to this task. If one reviews the developments in WMDs over the past several decades, clearly the introduction of national and international product performance standards has been one of the most significant advances. More recently, this advance has taken place in the development of the first industry standards for transport safety of occupied WMDs. This has taken the direction of two compatible standards; one for the WMD and the other for the occupant restraint belts and WMD tiedowns systems, with emphasis on the strap-type tiedowns. A considerable achievement is the fact that these standards are rapidly becoming implemented world wide through international harmonization efforts within the International Standards Organization (ISO).

In the U.S. the initial transit wheelchair standard, ANSI/RESNA WC/19, has the requirement that all transit wheelchairs must provide for securement using a four-point, strap-type tiedown that complies with SAE J2249. This is because the four-point, strap-type tiedown system is currently the most commonly used wheelchair securement system and it is a system that has been proven to be effective in hundreds of sled impact tests. It is clearly the most common system in use today, because it is the only system with the versatility to be used with a wider range of wheelchair types and models that have not been designed for securement in a motor vehicle. It is, in fact, today's universal securement system.

It is now clear, however, that there is a pressing need to move beyond strap-type universal securement systems to technologies that are more consistent with the goals of the independent living movement and the spirit of ADA (Architectural and Transportation Barriers Compliance Board, 1991), and that better meets the needs of the public transit environment. To achieve this next advance, requires the support and implementation of a bold and focused standards development effort. The seeds for this advance have been sown, largely by the past efforts of the RERC on Wheeled Mobility (1993-98). This work, involving the participation of the many key stakeholders, has taken a direction that proposes that rear–mounted docking technology is a feasible way to proceed towards enhanced transport for WMD users. Fundamental to providing universal access to independent docking securement for all WMD users, is reaching industry agreement on the geometric configuration of the interface device between the WMD and the vehicle-mounted securement device. Standards development work proposals have now been accepted at the U.S. national and ISO international levels and early debates have begun. The timetable for the first round of international voting and comment is scheduled for late Fall, 2001.

Progress in standards development is usually best made when participants can present reasoned arguments based on sound investigations, backed by laboratory validation. The leadership of this proposed RERC is currently the active leaders and contributors to both the ANSI-RESNA SOWHAT and ISO-WG-6 committees. It is the primary goal of this task to re-initiate the investigations and laboratory work necessary to prepare and present sound proposals in a focused effort to advance a universal docking interface geometry (UDIG) standard towards completion within a two year time frame.

Design of development activities

Technology used in development

There are many industry-based examples of how two technology entities have come together to agree upon how their respective technologies will interface with each other. Electronic connectors and computers, 18-wheel highway tractors and trailers, the international space station and its international delivery shuttles, utility trailers and automobiles, and the new NHTSA seat interface for latching child infant seats in family vehicles (NHTSA, 1999). User independence in securing wheelchairs to motor vehicles using docking technology appears, based on the study results of the earlier RERC, to be the best technological method to pursue, particularly when designing for safe securement in the high-g environment. Low-g environments will have less demanding securement loads that may not require the attainment of industry agreement on a universal interface geometry standard (UDIG) before product innovation can occur.

Work done over five years ago on the high-g environment has lead to the geometric interface configuration (UDIG) contained in the current draft standards. However, it is unlikely that this represents a definitive solution that will withstand the rigors of the multiple stages of national and international standards review, and therefore additional possibilities need to be carefully explored and the rationale for their consideration formulated. There are no known developments or technologies in the market place today that will meet the criteria required by the proposed UDIG standard.

Conceptual model

The conceptual model for the universal docking interface geometry (UDIG) standard is provided in the following illustration. In brief, it proposes an interface geometry that will allow a common method of docking securement between all types of WMDs and all types of vehicles commonly used to transport WMDs.

The salient requirements (taken mainly from Industry Summit II) for a successful UDIG configuration are as follows:

  1. Provide crash protection and safety in accordance with standards ANSI/RESNA WC19 SAE-J2249 (WTORS) (Society of Automotive Engineers, 1999; ANSI/RESNA, 2000)
  2. Hold the WMD in place during normal driving as defined by ADA
  3. Accommodate a wide variety of WMD designs and sizes
  4. Accommodate a variety of docking securement device configurations
  5. Require minimal manufacturer modifications to the WMD frame structure
  6. Be easy to use, aesthetic, and allow quick release in emergency situations
  7. Be marketed as an optional add-on feature that can be removed by WMD users that have no need for universal docking securement
  8. Be relevant and applicable in the majority of developed countries participating in the ISO-WG6 work.


ANSI/RESNA (2000). ANSI/RESNA WC19: Wheelchairs Used as Seats in Motor Vehicles, American National Standards Institute (ANSI)/Rehabilitation Engineering Society of North America (RESNA).

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

Karg, P., Bertocci, G. and Hobson D.A. (1998). Status of universal interface design standard for mobility device docking on vehicles. Annual RESNA Conference, Minneapolis, MN.

NHTSA (1999). FMVSS: Child Restraint Systems, Child Restraint Anchorage Systems.

Society of Automotive Engineers, S. (1999). SAE J2249: Wheelchair Tiedowns and Occupant Restraint Systems - Surface Vehicle Recommended Practice. Warrendale, PA, SAE.

Progress Report May 1, 2003


To provide leadership and support to the development of a universal docking interface geometry (UDIG) standard.

Results to Date

  • Computer simulations and laboratory measures regarding UDIG specifications undertaken
  • Results analyzed, documented and communicated to ISO standards working group
  • Results integrated into latest version of ISO 10542-3 stanadard
  • Editorial leadership provided to prepare document for DIS level national voting
  • Document sent to Geneva for international distribution for comment and approval voting
  • Plans formulated for evaluation of UDIG configurations on three test wheelchairs
  • Design and construction of test fixtures and wheelchair configuration initiated
  • Paper prepared and accepted for presentation at the RESNA-03 conference in June
  • Presentation of UDIG concept made at American Public Transit Association (APTA) meeting, May 03
  • STTR partnership formed related to securement technology for low ‘g’ transit vehicles ( subtask SP-3b)
  • STTR grant proposal to submitted NIH
  • Initial knowledge gathering plans for subtask SP3b initiated

*Task is slightly ahead of schedule as subtask SP-3b not scheduled to start until Nov. 03.

Progress Report May 1, 2004


Task 3a officially terminated on October 31/03—approximately 90 % complete. Effort is continuing on final validation using manual wheelchair crash testing.

Progress Report:

  • ISO FDIS 10542-3 :Docking Systems, which includes a normative specification for a universal docking interface geometry has been sent to ISO for final voting as an international standard.
  • A proposal for adoption of the ISO document as a US standard will be made in June –04.
  • A peer-reviewed publication is in process.

Progress Report May 1, 2005

Docking technology (ISO 10542-3-Docking Devices)

  • Successful validation crash testing of the UDIG adapter with two manual wheelchairs
  • Acceptance and publication as a international industry standard
  • Integration of the key requirements and UDIG specifications into Vol.4 of ANSI/RESNA national standards currently in preparation for US national balloting


Last updated: August 30, 2005