Douglas Hobson, University of Pittsburgh (retired)
January 20, 2009 [email]



see attached document


ADA Revisons-1-20-09

T203.8 Securement Systems. Securement systems complying with T403 shall be provided at each wheelchair space.

Comment: This requirement makes sense for all wheelchair space installations, excepting the rear-facing space in large vehicles. A main purpose of the rear-facing station is to allow independent use of the wheelchair containment station without the need for attachment of wheelchair securement devices, usually by the vehicle operator. To maintain the redundant requirement that securement devices that comply with T403 be provided, adds unnecessary cost, confusion and hardware clutter to the rear-facing station.

T203.9 Seat Belts and Shoulder Belts. Seat belts and shoulder belts complying with T404 shall be provided at each wheelchair space.

Comment: This requirement makes sense for all wheelchair space installations, excepting the rear-facing space in large vehicles. A main purpose and advantage of the rear-facing station is to allow independent use of the wheelchair containment station without the need for attachment of occupant restraints, usually by the vehicle operator. To maintain the redundant requirement that restraint devices that comply with T404 be provided in rear-facing stations adds unnecessary cost, confusion and hardware clutter to the rear-facing station.

T402.4 Size. Wheelchair spaces shall be 760 mm (30 inches) minimum by 1220 mm (48 inches) minimum. If wheelchair spaces are confined on all or part of three sides, additional maneuvering space complying with T402.4.1 or T402.4.2 shall be provided. Fold-down seats shall be permitted to occupy wheelchair spaces if the seat does not obstruct the wheelchair space when the seat is in the up position.

Comment: In general, recognition by this draft that additional maneuvering space is required by most wheelchairs is a positive revision. Regarding T402.4.2 a) forwardfacing, its probably impractical to suppose that flip down seats can be deployed to reclaim lost passenger space. The front wheelchair securement straps and its related anchoring hardware will become a tripping hazard to a person using the flip down seat.

T403.2 Design Force. Securement systems shall comply with T403.2.1 or T403.2.2, as applicable.

T403.2.1 Large Vehicles. On vehicles with a gross vehicle weight rating of 13,608 kg (30,000 pounds) or more, securement systems shall restrain a force in the forward longitudinal direction of up to 20 N (2,000 pounds) for each attachment or clamping mechanism, and 39 N (4,000 pounds) minimum for each wheelchair or mobility aid.

Comment: The 4000 pounds strength requirement for securement devices for use in forward facing stations in large vehicles is approximately double what is required. This unnecessarily high requirement limits the innovation of new products that can facilitate more rapid and independent use of buses by wheelchair users.
Multiple research studies have shown that under emergency driving conditions of maximum forward braking, the wheelchair and its occupant are highly unlikely to be subjected to g loads in excess of 0.85g. Emergency rapid swerving can generate maximum sideways (tipping) loads on the wheelchair in the range of 0.5g. Maximum acceleration on a horizontal road surface can create g loads in the range of 0.2g. In the event of an unlikely frontal collision, for example, with a large conventional automobile (3900lbs), with a delta V of 30mph, a maximum g load on the wheelchair will be in the range of 3g. This worst-case situation would result in the maximum forward longitudinal static strength requirements in the range of 1980 lbs (3g x 660 lbs).
Therefore: the strength requirement (maximum not minimum as stated) should be 2000 lbs not 4000 lbs as currently required.

T403.2.2 Small Vehicles. On vehicles with a gross vehicle weight rating of less than 13,608 kg (30,000 pounds), securement systems shall restrain a force in the forward longitudinal direction of up to 24 N (2,500 pounds) for each attachment or clamping mechanism, and 49 N (5,000 pounds) minimum for each wheelchair or mobility aid.

Comment: In contrast to a worst-case safety concern in large vehicles, this requirement must be concerned with the smaller para-transit vehicle, that may be operated at highway speeds containing a wheelchair-seated passenger. In accordance with federal regulations (49 CFR part 571), all passenger seats must be secured to the floor and provided with occupant restraints that meet specified design requirements. These requirements include dynamic testing to a 30 mph/20g frontal crash pulse. Since there are no federal regulations for devices for securing a wheelchair in small vehicles, a US voluntary industry standard was developed that has been in effect since 1996. This requires the same level of crash pulse (30mph/20g) test as the occupant restraint. This crash pulse can produce a total rear wheelchair securement force as high as12000 lbs., which is more than twice that called for in T403.2.2.
Today, virtually all wheelchair tiedown and occupant restraint systems (WTORS) devices manufactured and used in the US, in both public and private vans, meet this industry standard (SAE J2249, to be renamed ANSI/RESNA Volume 4, part 18).

Therefore, in the interests of all passenger safety (wheelchair user and other passengers), and the elimination of the requirement for the manufacture and use of a WTORSs that do not meet either federal or industry safety regulations, it is strongly recommended that all ADA-compliant small vehicles be required to install WTORS devices that comply with SAE J2249.

This revision of ADA still allows rear-facing wheelchairs in small vehicles. This is wrong. To date, all standards-compliant products have been tested only under simulated frontal crash conditions with the occupant in the forward-facing orientation. As a result, there are no products in the marketplace that have been safety-tested for use with rear-facing wheelchairs transported in small (para-transit) vehicles. Furthermore, available research and current usage clearly indicates that the rear-facing concept, even when a padded head and back barrier is provided, was never designed and tested to withstand the high loads that will be sustained by a rear-facing wheelchair and its occupant in the event of a frontal vehicle crash in a small vehicle. Furthermore, it is unlikely that safety-tested products will become available in the near term.
Therefore, it is strongly recommended that ADA only allow forward-facing wheelchair orientation in small vehicles, i.e. those with a GVWR less than 30K lbs.

Advisory T403.3 Movement. Securement systems are provided for passengers who want their wheelchairs and mobility aids secured. The restricted movement requirement does not apply to wheelchairs and mobility aids which are not secured by a securement system, including wheelchairs and mobility aids in rear-facing wheelchair spaces.

Comment: Of all the revisions in this section this is the most troubling. This now says that the only purpose of securement systems is for the OPTIONAL use of passengers who want their wheelchairs secured. Through lack of qualification of this advisory, this can be interpreted to apply to all sizes of vehicles.
Federal regulations, for the sake of the safety of all passengers, mandate that the vehicle seats must be fastened to the vehicle floor in accordance with applicable strength requirements. To allow a seat, in this case an occupied wheelchair, to travel unsecured, especially in a small vehicle, places not only the wheelchair user but also near-by passengers at high risk of injury.

Therefore, this advisory statement must either be deleted or revised to remove the optional use of wheelchair securement in all sizes of vehicles, excepting the rear-facing station when used in a large vehicle.

T403.5 Padded Head Rest. If securement systems are positioned so that wheelchairs and mobility aids face the rear of the vehicle when secured, a padded head rest complying with T403.5 shall be provided at the back of the wheelchair space.

Advisory T403.5 Padded Head Rest. The padded head rest is intended to reduce the possibility of whiplash in a sudden stop. The padded head rest must be positioned approximately in line with the plane of the wheelchair or mobility aid backrest, and the bottom edge of the head rest is required to be above the approximate height of the backrest. Many wheelchair users have backpacks on their wheelchairs. If the bottom edge of the padded head rest is below the top of the backrest, the head rest may encounter the backpack and prevent the wheelchair from being positioned close to the head rest.

Comment: Its is difficult to imagine a better scenario for causing serious injury to wheelchair-seated passengers than what is now being proposed for the rear-facing wheelchair station, particularly if the option for its use in small vehicles remains.

A fundamental tenet of rear-facing occupant protection is that if a head support is vehicle- mounted, a reliable wheelchair stop must also be provided. That is, if the wheelchair and its occupant moves forward in the vehicle during a braking or a frontal collision event, the occupants head and neck will be snapped forwards (towards the rear of the vehicle) by contact with the immoveable head rest. Therefore, the primary purpose of the forward excursion barrier (FEB) in a rear-facing installation is to first, limit forward movement of the wheelchair, and second, limit the forward movement of the occupants head and upper torso. To accomplish this the FEB must extend far enough to down to come in contact with the wheelchair seat frame or lower back rest. For adult wheelchairs this height from the floor to the lower FEB is a minimum 400, maximum 480 mm. Yes, there will be back-packs on some wheelchair backs that can prevent (depending on the FEB design) close proximity between the persons head and back and the FEB. However, in a 1g environment typical of large transit vehicles, lack of proximity is a lesser problem than having the forward movement of an occupied wheelchair being stopped by its occupants head and neck.

Finally, figure T403.5 (a) elevation is misleading. It suggests that the rear-wheels of the wheelchair are backed against a vehiclemounted stop. Inspection of (b) plan shows that the only forwardmovement stop is the head rest. Also, the heading for this section needs to be change to Padded Forward Excursion Barrier, which is a term that encompasses both the wheelchair and the occupants head and upper torso.

T802.2 Slip Resistant. Surfaces shall be slip resistant.

Comment: Without an attempt at qualification, the above requirement is impossible to comply with since interpretation of the requirement is totally subjective. In climates where floor surfaces can become wet , slick, and wheels icy, the coefficient of friction (CoF) between the floor surface and the wheelchair tires becomes an important safety factor. This is especially important in the case of a rear-facing station in which the limitation of wheelchair movement can be dependant solely on the braked rear wheels. Vehicle floor materials are available with a range of CoF from 0.5 to 0.8.

Therefore, it is recommended that floor materials used in rear-facing stations have a coefficient of friction in the range of 0.7 to 0.75, with materials in forward-facing stations having a CoF value no less than 0.65.




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