UDIG: Universal Docking Interface Geometry

As vehicle manufacturers work to design integrated wheelchair seating stations for automated and other vehicles, they have sought solutions that could allow people who travel in their wheelchairs to dock independently when there may be no driver or caregiver available to assist. Consequently, there has been renewed interest in the Universal Docking Interface Geometry (UDIG) that has been published in wheelchair transportation standards for many years. UDIG defines just the interface shape and location. Allowing a wide variety of designs of wheelchairs and securement systems to comply. With the UDIG concept, any wheelchair with UDIG-compatible hardware should be able to dock in any vehicle with a UDIG-compatible anchor. The idea is akin to the tractor-trailer hitch, where any heavy truck tractor can connect to any trailer because there is a common interface geometry.

Animation of UDIG concept (credit: Kyle Boyle)

On wheelchairs, UDIG specifies the size and location of two vertical tube components that are located behind the wheelchair with a optional horizontal element. The hardware elements are not allowed to extend past the rear wheels, so will not make a wheelchair longer. Locating the attachments behind the wheelchair means there won’t be floor clearance issues that can be a problem with the docking bolt/plates below the chair used in traditional docking stations. The UDIG tolerances makes it easier to dock on the first try compared to traditional docking systems, too. The height of UDIG anchors is close to the wheelchair occupant center of gravity. This reduces securement loads and undesirable forward rotation of the wheelchair during frontal crashes.

Prototypes based on this concept have been evaluated in several vehicle types and crash tested to high deceleration pulses. Several recent UMTRI projects have designed prototype attachments for five different commercial wheelchair models. We have also developed prototype securement anchors that have been successfully installed in different modified vans (including an electric vehicle with batteries in the floor) and evaluated by volunteers who are experienced wheelchair users. Based on feedback from manual wheelchair users stating that it is undesirable to add unnecessary weight to the wheelchair, we have been able to design attachments that weigh only 2 lbs. A universal securement system like one designed using UDIG has the potential to provide greater accessibility and usability across several public transportation platforms (automated or not), such as buses, taxis, ride shares, trains, airplanes and more.

Pictures of add-on UDIG attachments for five different wheelchairs
Examples of add-on UDIG attachments for five different commercial wheelchairs.