STANDARDS AND ANTHROPOMETRY

FOR WHEELED MOBILITY

REPORT PREPARED FOR:

U.S. ACCESS BOARD, WASHINGTON, DC

Authors:

Edward Steinfeld

Jordana Maisel

Dave Feathers

July, 2005

Center for Inclusive Design and Environmental Access (IDEA)

School of Architecture and Planning

University at Buffalo

The State University of New York

Buffalo, NY 14214-3087

This report, the workshop’s papers and the presentations are available on the World Wide Web:

http://www.ap.buffalo.edu/idea/Anthro/index.asp

Preface

This report was prepared at the request of the Board to provide guidance in the further development and revision of the ADA-ABA Guidelines and in providing technical assistance to designers and code developers. It builds on research completed as part of the Rehabilitation Engineering Research Center on Universal Design at Buffalo from 1999 – 2004.

The authors thank the researchers who responded to our requests by providing copies of their original reports. We hope that the data and observations in the report can be useful to anyone interested in the state of accessibility standards and research related to space requirements for wheeled mobility.

Disclaimer

This report and some of the anthropometry research described here was developed with funding from the U.S. Access Board (contract # TPD-02-C-0033). The bulk of the anthropometry research was completed with funding from the National Institute on Disability and Rehabilitation Research (NIDRR) through the Rehabilitation Engineering Research Center on Universal Design at Buffalo Project (grant #H133E99005). The contents do not necessarily represent the policy of the Access Board or NIDRR and readers should not assume any endorsement by the Federal government.

Contact Information

For further information, contact:

Edward Steinfeld, Director

Center for Inclusive Design and Environmental Access (IDEA Center)

School of Architecture and Planning

University at Buffalo

3435 Main Street, 378 Hayes Hall

Buffalo, NY 14214-3087

716.829.34585 ext. 329 (phone)

716.829.3758 (TTY)

This document is available free of charge from the IDEA Center website at:  http://www.ap.buffalo.edu/idea/Anthro/index.asp

Ó Copyright, IDEA Center, 2005

Unlimited use of this document for educational and research purposes are permitted without written permission but altering the contents and distribution for sale is not allowed without prior written permission from the IDEA Center. 

Executive Summary

Standards for accessible design include requirements based on the anthropometry of wheeled mobility users. Key requirements apply to clear floor area, reach limits, knee and toe clearances and maneuvering clearances. Advisory information is also often included on the characteristics of mobility devices. The U.S. standards are based on research completed in the late 1970’s. Advances in wheeled mobility technology and demographic changes that have occurred since that time suggest that the U.S. standards may be out of date. Since that time, research on the anthropometry of wheeled mobility users has been conducted in Australia, the United Kingdom and Canada. All those countries have revised or are revising their standards based on that research. The IDEA Center has been collecting data on wheeled mobility users for five years and data collection will continue at least through 2006. Enough data has been collected to start a dialogue on the significance of the findings.

The research in the U.S. and the three other countries were reviewed and compared to identify needs for improving standards. Many differences were discovered in both the standards and research studies. Although research results differ, trends in the data support making many important revisions to the U.S. standards to address the reality of contemporary wheeled mobility use. But, since research methods differ from study to study, there is a need for a close analysis to understand the findings and apply them appropriately. Most of the studies were not well documented and raise many questions about the results. The IDEA Center study is well documented and provides a flexible data set to complete many different types of analyses, not all of which have been included in the present report. The comparative analyses developed for this report provide a framework for the future comparison of research findings and standards and offer a foundation for improving the utilization of research for standards development.

The analysis highlighted the importance of integrating research with standards development, organizing international research collaborations and developing international standards. Previous and ongoing research at the IDEA Center supported by the Access Board provides a foundation for all three activities.

1.0 Background

The standards used to ensure accessibility for people who use wheeled mobility devices like wheelchairs and scooters are based on research in anthropometry, the measurement of body sizes and physical abilities. The anthropometric data on wheeled mobility users that underlies the technical requirements of the ICC/ANSI A117.1 (1998) Accessible and Usable Buildings and Facilities (ICC/ANSI) and the ADA Accessibility Guidelines (ADAAG) were generated from research completed from 1974 -1978 using a research sample that included about 60 individuals who used wheelchairs (see Steinfeld, et al., 1979).

In 25 years, many changes have occurred in the stature of the U.S. population, the characteristics of people who use wheeled mobility devices and the characteristics of equipment that they use. Yet, the technical requirements have not changed. In fact, until recently, a newer anthropometric data set on wheeled mobility users in the U.S. was not available. In response to this lack of current information, the IDEA Center has been developing a comprehensive data set with a high level of accuracy (Steinfeld, Feathers and Paquet, 2005; Feathers, Paquet and Drury, 2004; Paquet and Feathers, 2004). Although data collection is ongoing, we have now achieved a sample size and breadth that we believe is sufficient to start a dialogue about the needs for revision to current standards.

Comparisons of international standards and research are useful to validate methods and confirm results. They are also useful to identify best practices and differences related to cultural factors. In this report, we present a comparative analysis of research and standards on wheeled mobility in the U.S., the U.K., Australia and Canada. The analysis was limited to wheeled mobility device dimensions, minimum clear floor areas, space requirements for maneuvering, knee and toe clearances and reach limits.

This report compares the national standards from these three countries and the U.S. It also compares the research findings from the various studies, including the current work at the IDEA Center, to the standards. Section 2.0 describes the methodology we used to make these comparisons. Section 3.0 includes a comparison of the research studies’ methodologies. Section 4.0 provides a graphic comparison of the standards and research studies and a discussion of the findings and recommendations. Section 5.0 provides a conclusion. The Appendix includes details of the research methodologies, photographs illustrating issues in the report, a summary table of the IDEA Center research results and references.

2.0 Methodology

We reviewed ICC/ANSI A117.1 (1998) Accessible and Usable Buildings and Facilities, which serves as the model for the technical requirements in the federal guidelines in the U.S., the Americans with Disabilities Act Accessibility Guidelines (ADAAG) and its eventual replacement, the Americans with Disabilities Act – Architectural Barriers Act Guidelines (ADA-ABA). For the United Kingdom (U.K.), we reviewed BS 8300:2001 Design of Buildings and Their Approaches to Meet the Needs of Disabled People – Code of Practice. For Canada (CA), we reviewed B651-04 Accessible Design for the Built Environment. For Australia (AUS), we reviewed AS 1428.2 – 1992 Design for Access and Mobility Part 2: Enhanced and Additional Requirements – Buildings and Facilities.

Since the findings of anthropometric research are often voluminous, journal articles and book chapters do not usually include a full documentation. Thus, we obtained the original research reports from Ringaert, et al. (2001) from Canada, Stait et al. (2000) from the United Kingdom, Bails (1983) and Seeger et al., (1994) from Australia. The research underlying BS8300:2001 in the U.K. was summarized in an Annex to the standard itself but we were unable to obtain a more comprehensive report that described the details of the methodology.

We first compared the relevant criteria in all the U.S. standards to identify the common underlying anthropometric variables. Our analysis then focused only on these variables. The common variables were defined graphically in illustrations and with abbreviations, e.g. Knee Clearance Height (KCH), Knee Clearance Depth – Upper (KCDU), Knee Clearance Depth – Lower (KCDL) and Extended Depth (ED). In many cases, variables underlying the U.S. standards are not included in other standards. Thus, in our comparisons, we simply omitted values for those variables. We did not, however, report variables from other standards that are not included in the U.S. standards.

The standards did not use the same variables (or parameters), terminology or measurement conventions. For example, the U.S. standards include both Imperial and “soft” conversions to Metric units, but all the other standards are in Metric units only; there are at least three different terms used for a “wheelchair turning space,” and the U.K. standards report reach ranges for both a “maximum” and “minimum” reach while the U.S. standards have only one range delimited by a minimum and a maximum value. These differences present several problems to researchers. For example, the definition of a “wheelchair turning space” determines the protocol used to study the clearance needed. Different results are obtained if that space is bounded or unbounded or whether the protocol calls for a smooth continuous turn or includes a series of smaller movements or allows either. Since the standards do not define variables clearly, researchers have made their own interpretations and developed different protocols to study the same variables. Thus, to make comparisons, we standardized all the values from standards and research as much as possible based on a common definition of variables and measurement conventions. We reported the U.S. values in both Imperial and Metric units but did not convert the other countries’ values to Imperial nor did we do “hard” conversions of the U.S. Imperial values.

We then reviewed the research completed in each country since 1980; the year after the research of Steinfeld et al. (1979) was published. In many cases, this required some interpretation because the research studies did not always use the same terms or definitions as the standards in the respective country. Different approaches were also used to report findings. Some results were reported in percentiles. Other results were reported as minimum or maximum values. Still others were reported as the “percentage of subjects accommodated” – those who could perform a task at a certain criterion level. We devised a graphic method to compare the results of the research studies to each other and to the standards. Most of the studies reported at least a minimum or maximum value and a mean value for each variable studied. These three points were displayed on a graph and coded by study. Where available, percentile data was added to the graph in between the minimum and maximum values and the mean to provide more detail. All the values for each study that represented a distribution were connected by line segments.

Some studies focused on a very limited set of variables. Because of the methodology used in the IDEA Center anthropometry research, however, we were able to compute results for all the variables and all relevant statistics. Thus our results appear in all the analyses and can be compared to all the standards.

3.0 Comparison of Research Methodologies

There were many differences in the research studies, including the documentation provided, samples recruited, methods used and data reporting formats. Table 1 provides a summary of the main differences. The sub-sample studied for any sub study could differ greatly from the total sample size and was not always documented. (Refer to Appendix 1 for more detailed descriptions of the methods used in each study.)

Table 1.  Overview of Research Studies

Study	Sample	Methods	Reliability	Scope
Bails, 1983, AUS	Total unknown, manual and power chairs, from institutions	2-D, manual	No reliability or validity study	Body and device size, reaching, maneuvering, door use
Seeger, Costi and Hartridge, 1994, AUS	240, all devices. 75% from institutions	2-D, manual measurements	No reliability or validity study.	Body and device size
Department of the Environment, Transport and the Regions (DETR): Stait, Stone and Savill, 2000, U.K.	745, all devices, attendees at Mobility Roadshow	2-D, photography with digital measurements	Reliability study	Body and device size
BS8300: 2001 Appendix (research commissioned by the DETR), U.K.	164, all devices, but only 91 for space allowances, source unknown	Not reported.	Unknown	Body and device size, knee and toe clearances, reaching, maneuvering, door use
Universal Design Institute (UDI): Ringaert, Rapson, Qui, Cooper and Shwedyk, 2001, CA	50, power chair and scooter users, diverse sources	2-D, manual measurements, detailed interview	No reliability or validity study	Body and device size, reaching, maneuvering
IDEA Center: Steinfeld, Paquet and Feathers, 2005, U.S.	275, all devices, diverse sources	3-D, digital probe, video, detailed interview	Reliability and validity study	Body and device size, reaching, maneuvering, door use

Bails (1983) recruited participants from attendees at disability support centers and institutions. Eligible participants were between 18 and 60 years of age and used a manual or powered wheelchair. Scooter users were not included in the study. The total sample size is not known. The research focused primarily on testing of full-size simulations of elements found in the built environment, such as doorways, environmental controls, furniture and fixtures that were configured to meet the Australian standards at the time. Many of the findings, therefore, could not be used to make generalizations or to determine the ideal spaces needed for access.

Seeger et al. (1994) studied only device size. About seventy-three percent 73% of the 240 individuals in the sample lived in nursing homes and other institutions. Forty-five percent were over 65. Eleven percent used power chairs and two percent used scooters. Both unoccupied and occupied dimensions of device width and length were measured as well as a set of other basic dimensions. Measurements were taken manually using conventional measuring tools including a tape measure, steel square and spirit level. 

The DETR study (Stait et al., 2000) was limited to measurement of device size and weight. Participants in the DETR study were recruited at an exposition of equipment for people who use wheeled mobility devices for traveling around the community. Of the 745 participants whose data was acceptable, 59% used self-propelled manual chairs, 9% used attendant powered chairs, 25% used power chairs and 9% used scooters. Nine percent of the sample were judged to be 16 years of age or younger. Two cameras were used to take photographs of the participants from top and side after they wheeled into position on a scale. A checkerboard pattern on the floor and wall provided references to take measurements off the photographs. Parallax was corrected during the calculation of the dimensions. Prior to data collection the reliability of the method was verified by comparing dimensions taken directly from individuals with those calculated from photographs. Device dimensions were defined clearly. Although a wide variety of accessories were observed on the devices, they were not measured as part of the width calculation.

The BS8300:2001 research covered knee and toe clearances, reaching abilities of wheeled mobility users, clear floor area space requirements and maneuvering clearances. A total of 164 individuals were included in the sample but only 90 participated in the research on space allowances. Due to the lack of a full research report, it is not clear how the measurements were collected and, in many cases, the landmarks used to define them. From the information available, it appears that some scooters and attendant propelled chairs were included in the sample but it is not clear whether these individuals were included in the device, body or reach measurements.

The UDI study (Ringaert et al., 2001) was recruited from disability and senior organizations in Winnipeg by written invitation. Of the 50 participants, 35 used power chairs and 15 used scooters. The cause of disability for individuals in the sample included a wide range of conditions. Device size, maneuvering space needed and reaching ability were measured. All dimensions were taken to the extremes of the equipment including any object attached to the device like a ventilator. However, the actual landmarks on the devices are not well documented. Measurements were made with rulers and tape measures but no information is given on the accuracy and reliability of these techniques. Maneuvering trials were recorded using overhead video cameras while participants completed standardized movements in simulated environments built with plywood floors and wood framed dividers. Measurements were later taken off the videotapes although the method used to do this and the reliability of the technique are not described. An observer rating was used to determine successful trials.

The IDEA study (Steinfeld, Paquet, Feathers, 2004; 2005; Feathers, Paquet, Steinfeld, 2004; Paquet and Feathers, 2004) included static anthropometry of occupied wheeled mobility devices, reach measurements and measurements of maneuvering clearances. At the date of the analyses conducted for this report, 275 participants with a wide range of chronic conditions had been recruited through outreach efforts with several organizations in Western New York and mass media. Fifty-three percent of the sample was male and 47% female. The mean age of the sample was 51.5 with a range of 18-94 years of age. Fifty-five percent used manual wheelchairs, 36% used power wheelchairs and 9% used scooters. Three-dimensional locations of body and wheelchair landmarks were collected with an electromechanical probe (Feathers, Paquet and Steinfeld, 2004). A reliability study was completed before data collection (Feathers, Paquet and Drury, 2004). The reach protocol utilized a standardized procedure in which participants reached to a target (free reach) and also while lifting .46, 1.4 and 2.3 kg (0, 1, 3 and 5 lb.) weights. Reach limits were digitized with the mechanical probe, and, from the data, a reach envelope for each individual was constructed. Maneuvering clearances were measured while participants conducted standardized maneuvers inside a set of lightweight movable walls. The walls were gradually moved further apart until the maneuver could be completed without the participants moving the walls. Clearances were pre-measured on the floor of the test site using tape and marker and the locations of walls were recorded after each trial.

The studies utilized widely different methods to recruit participants. The DETR study has a large sample size but the participants were all self-selected in their interest and ability to attend the Mobility Roadshow. Thus the sample is likely to be more mobile than the wheeled mobility population as a whole and their choice of chairs may reflect that. A high rate of unusable data due to problems with photography may have introduced some sampling bias as well. The Seeger and Bails samples were drawn primarily from institutional settings, which would definitely introduce bias in the types of devices used and maneuvering abilities. Both the IDEA and UDI studies recruited a diverse sample and provided transportation to the research site ensuring that low mobility would not be a barrier to participation. However, in both cases, the samples could not be considered representative of the entire population of wheeled mobility users in their respective countries. Users of powered chairs, are definitely overrepresented in the IDEA sample. The UDI study did not include manual wheelchair users at all. It should be noted that overrepresentation of one group or another is not necessarily bad because it can help to address lack of attention to specific populations.

The UDI and Bails studies had very small samples. Bails, in particular, had sub samples for some of his protocols that included as few as five individuals. In the U.S. we calculate that the bare minimum size of a sample that would represent the U.S. population of wheeled mobility users would be 500. Although the current size of the IDEA Center sample (275) is the largest assembled in the U.S. and is almost five times larger than the study on which ANSI A117.1 (1980) was based, it still cannot be considered a representative sample on size alone. It is important to note that, in this type of research, total sample size is not as important as inclusion of a diverse group of users, enough people in each category to cover the range of abilities and sizes and spending enough time with individuals to obtain a comprehensive data set. Powered device users were over-sampled on purpose in the IDEA sample because the technology has changed so much since 1979 and the users of powered devices are more seriously impaired.

A limitation of both the IDEA sample and the UDI sample is that they are drawn entirely from cold weather cities. This may introduce some bias toward larger and more durable equipment. Data was collected all year round in the IDEA study so that season should not have introduced a bias in recruitment, however, the UDI study was conducted only in winter which may have influenced participation. The IDEA sample is growing more representative as time goes on as we target new recruitment to underrepresented groups. We are planning on collecting data in two additional cities, one in a hot climate and one in a city with hilly terrain. We have made a concerted effort to promote the use of our methods so that other researchers can contribute data to merge into our existing database.

The methods Bails and the BS8300 used are not reported in detail. Without the details, it is difficult to evaluate them. The reliability of measurements taken in the UDI and Seeger research is not known. It appears that UDI did not address issues of distortion caused by camera lenses in their analysis of some maneuvering trials. Both UDI and Seeger used rulers and tape measures rather than more accurate anthropometric instruments designed for such a purpose. In the UDI research, the lack of a reliability study to determine the level of agreement among researchers to rate the level of “accessibility” observed is a key limitation because those ratings were used to determine success in managing specific space clearances. The IDEA and DETR studies are very well documented and reliability studies were completed in the preparation phase.

UDI’s research was focused on validating the B651-95, precursor to the B651-04. All the maneuvering trials started with the clearances in the standard but the results of fitting trials can be influenced by the starting position. In contrast, the IDEA Center research started with the smallest possible clearance. We discovered that many of our participants could manage maneuvers in much smaller spaces than the minimum clearances of the ADAAG.

The reach protocol used by the IDEA Center did not collect data on the lowest reach possible because of safety concerns. Lowest reach was obtained for free lateral reach without bending but this cannot be used to represent the lowest forward or extended lateral reach. It is not known how the UDI researchers addressed the safety concerns related to low reach but it is clear that differences in human subject approval procedures certainly can influence the methodologies used.

DETR, UDI, the BS8300 researchers and IDEA provided results in percentile form. This is very valuable for making decisions about criterion values. Ideally, standard deviations and median values should be provided at a minimum so that all percentiles can be calculated. BS8300 failed to include median values so percentiles other than what they reported cannot be computed. UDI, Bails and the BS8300 researchers did not provide any information on whether outliers were identified and eliminated from the data reported.

Section 4.0 Findings

4.1 Wheeled Mobility Device Dimensions

Figure 1 and Table 2 show the standards from the four countries and the variables they include on wheeled mobility device sizes. Selected research findings are shown in Figures 2-8.

Table 2

	U.S.*	Australia	Canada*	U.K.*
Unoccupied Width	660	X	660	X
Unoccupied Length	1065	X	X	X
Handle Height (HH)	915	X	920	X
Armrest Height (AH)	760	X	760	x
Seat Height (SH)	485	X	480	480
Folded Wheelchair Width (F)	X	X	300	X
Occupied Width (W)	X	X	X	X
Occupied Length (L)	1200	X	1200	X
Eye Height (EH)	1090-1295	1250	1100-1300	X
Knee (Lap) Height (KH)	685	X	675	X
Toe Height (TH)	205	X	200	X
Toe Extension beyond Footrest (TE)	150	X	X	X

Figure 1

** Advisory information

Figure 2. Unoccupied Device Width

Figure 3. Unoccupied Device Length

The research data shows that the sizes of devices vary considerably from the values in the standards. The sizes described in the standards are close to the mean values found in the research studies but this is certainly not sufficient to accommodate a large enough proportion of wheeled mobility users. For example, the IDEA data for mean unoccupied length is identical to the standard. But, the widest device measured was about 150 mm wider and the longest more than 200 mm longer.

The data also indicates that armrest height and handle height vary considerably from the values included in standards but only for the extremes of the population (see figures 4-6). The means for these two variables were very close to the value in the standard in all three studies that measured it. In contrast, the mean seat height was above the value in the standard for the two studies that measured it and the difference between the value in the standards and the results is considerably larger than for armrest height and handle height.

Figures 4-5. Armrest Height

Figure 6. Handle Height

* One outlier removed due to data translation errors in software

The two studies that measured seat height discovered that the values in the current standards are below the means of the research results. This is probably due to the increased use of positioning systems, thick cushions and the availability of a wider range of wheel sizes since the 1970s but it can also be due to differences in measurement methods. The height of the seat can be measured at the edge and at the middle, under the cushion, or on top of the cushion. Thus, specifying exactly how it is measured is important for comparing results. In the IDEA research, the height of a seat plane was defined and also measured at point at the rear of an individual’s buttocks using an extension of the electromechanical probe that we slipped down behind an individual’s back. The results would clearly be different compared to other measurements, particularly if the measurement was taken at the leading or trailing edge of the seat below the cushion.

Figure 7. Seat Height

* Two outliers removed from IDEA Center data due to translation problems in software

For eye height, the findings are extremely consistent. They show that the means are well below the values in the standards. The maximum values for the UDI, Seeger and IDEA studies are just slightly above the standard value. These results may be related to the increased use of thick cushions since the 1970s and elevated seating systems that position smaller individuals at a more functional height. The earlier research may not have included people of very small stature.

Figure 8. Eye Height

When the ANSI A117.1 (1980) Standard was developed, there was a true “standard adult manual wheelchair” but that is not the case today. Wheeled mobility technology has changed significantly and it is likely to continue changing. Many new types of devices have appeared on the market, both larger and smaller than the “standard adult wheelchair” of the 1970s and devices are fitted and customized more often to suit the needs of an individual. In the U.S., as the average weight of the population has increased, wheelchair manufacturers started producing wheelchairs with larger capacity and many more seat widths. 

To provide realistic guidance for designers, information on wheeled mobility dimensions should include occupied sizes as well as device size and also include accessories as they are used in everyday life. Occupied device sizes are clearly preferable and more useful for designers than unoccupied sizes but it is not uniformly provided in the standards. For example, in the U.S. standards, only occupied length is shown whereas the width is based on the device alone. Unoccupied device size is important also because it defines the absolute bottom line for small clearances, e.g. knee clearances or closet openings. It is important to note that although data on device sizes is available from manufacturers, it does not include actual dimensions as set up for individuals nor does it provide data on added equipment like seating systems, cushions, control boxes, ventilators, carrying baskets and other accessories. In this regard, not all the studies measured unoccupied dimensions or included accessories as part of their dimensions and measurements (e.g. Stait et al., 2000).

Data on occupied device sizes is most valuable for establishing clear floor area requirements. Thus, if occupied sizes are included in standards, it is important that they be consistent with the specified clear floor areas. Data on armrest, seat, and eye heights can be very useful for designers but it also can be misleading if not enough detail is provided. Design for extremes of a range may help only a very few people, yet design for the mean or median may exclude those in the extremes which may be very useful in the design of facilities that large numbers of wheeled mobility users may inhabit on a daily basis. If this data is reported in the standards, it should include enough information and guidance for designers to make informed decisions about how it is to be used.

The inclusion of handle height in the standards is of questionable value. We could not identify any need for this data. On the other hand, it would be useful to have information on accessory dimensions like control boxes and ventilators.

The illustrations used to depict wheeled mobility devices in the U.S. Australian and U.K. Standards are manual wheelchairs. The Canadian standard, however, includes illustrations and data on scooters and power chairs. This information can be very valuable to designers who are seeking to ensure full accessibility beyond minimum required levels. Additional illustrations are needed to convey the diversity in the devices and their occupants. Designers could also benefit from more information on device size to plan spaces like storage areas for wheelchairs at transportation terminals or the design of counter edges in relationship to armrests. For example, the U.K. standard includes data on the width of folded wheelchairs. Accurate and reliable data on device size may be more appropriate to provide in a reference manual with more detailed information and extensive illustrations of different equipment types in use.

Recommendations

• Provide illustrations of seven types of devices in an advisory section: attendant propelled manual chairs, old style manual chairs, lightweight manual chairs, power assisted chairs, power chairs with rear wheel drive, power chairs with mid wheel drive, scooters.
• Provide data on key characteristics of wheelchairs as used by individuals:
• Occupied width
• Occupied length
• Knee height
• Seat height
• Toe height
• Armrest height
• Eye height
• Head height (currently not included in the Guidelines but useful for vehicle design and also locations where lifts are installed that may not have sufficient headroom)
• Weight (currently not included in the Guidelines but critical for designing lift capacity and structural loads for ramps)
• For advisory purposes, provide statistical information on each variable from which percentile data can be calculated:
• Min-max values
• Standard deviation
• Median
• Update criteria that are based on the above dimensions. This includes but is not limited to clear floor areas, shower seat height, toilet height.

4.2 Clear Floor Area

Figure 9 and Table 3 show the standards from the four countries related to clear floor area. Figures 10-13 show the key findings from the research.

Table 3.

	U.S.	Australia	Canada	U.K.
Width (W)	760	800	750	900
Length (L)	1200	1300	1200	1350

Figure 9.    

Figures 10-11. Clear Floor Area (Occupied) Width for All Devices

Figures 12-13. Clear Floor Area (Occupied) Length for All Devices

Recent revisions to standards in Australia and the U.K. have increased the clear floor area dimensions in both width and length. The U.K. requirements, in particular, are much larger requirements than those in the U.S. and Canada. Research results support larger dimensions. All the studies found that wheeled mobility devices vary from the standards significantly in both width and length. While there are many occupied devices that are narrower and shorter than the values in the standards, the largest devices are generally above the minimum width and length in the standards.

The findings on clear floor area are based on the findings on occupied width and length, where provided. The DETR study did not collect data on occupied width (see previous section). The authors argued that individuals can bring their arms and legs inboard when entering transportation vehicles and passing through doorways. We found, however, that many individuals cannot bring their body parts “inboard”.

The IDEA Center research results for occupied width were smaller than those of the Seeger study. No study reported widths larger than 850 mm. The BS8300 research did not report occupied widths larger than 800 mm but the BS8300 standard, as we interpret it, requires 100 mm more than that for the clear floor area width (900mm). The BS8300 standard’s developers may have added 100mm to provide additional maneuvering room at clear floor areas.

In all the studies that reported data by device type and percentile, the occupied widths of the smallest and largest power chairs were generally the same as the occupied widths of the manual chairs. Occupied widths of scooters were narrower with the exception of the IDEA Center findings. This can be attributed to the presence, in the IDEA scooter sub-sample, of some very large individuals and some who keep their legs outside the edge of the chair when in a resting position. Other studies may not have measured people in “resting” postures. The larger sizes of Americans may also contribute to this difference.

The largest occupied lengths all exceed the current standards, even the U.K. standard of 1350mm. However, the results show that the 95^th percentile values are between 1200 and 1350 mm. The difference between the maximum length in the UDI and Seeger studies and the others is so great that it is probably due to the presence of unusually large people and/or devices or measurement error. The maximum length (occupied) recorded in the UDI study, for example, was over 2000 mm (over 6 ft.- 8 in.)! In the case of Seeger et al.’s work, we know that most of the sample was recruited from institutions and many may have had extended foot rests or reclined backs on their chairs. No information is provided in the reports to assess whether individuals in either study could be considered outliers. For example, the other studies together included over 1200 individuals and no other study reported a device as long as 2000 mm. Such a large value is likely to have been a measurement error or a very unusual case such as a person who uses a small all terrain vehicle for mobility.

The research results clearly suggest that clear floor areas be increased to address the actual size of contemporary occupied devices. Although there are differences in the findings, they can be attributed to methods and reporting approaches.

Recommendations

• The clear floor area width should be increased in the U.S. standards. A width of 800 mm (31.5 in.) would accommodate the 95^th percentile in the IDEA sample
• The clear floor area length should be increased in the U.S. Standards. A length of 1400 mm (55 in.) would accommodate the 95^th percentile in the IDEA sample

4.3 Reach Ranges

Figures 14-15 and Table 4 show the standards from the four countries related to reach from a wheeled mobility device. Figures 16-19 show key findings from the research.

Figures 14-15.  Forward and Lateral Reach

Table 4

	U.S.	Australia	Canada	UK
Unobstructed
High Forward Reach (HF)	1220	1220	1220	x
Low Forward Reach (LF)	380	250	380	x
High Side Reach (HS)	1370	1350	1400	1060-1170
Low Side Reach (LS)	380	230	230	630-665
Obstructed
High Forward Reach	1120	R.E.	1100	1000-1150
Low Forward Reach	x	x	x	650
High Side Reach	1220	1170	1200	x
Low Side Reach	x	x	x	x

*R.E. = Reach Envelope

The U.S., Canadian and Australian standards are similar, although the latter use a reach envelope to provide guidance for obstructed forward reach and both the Australian and the Canadian standards are less restrictive for low side reach. On the whole, the U.K. standards proscribe much more restrictive reach ranges although they do include different limits for different types of applications.

Figure 16. High Forward Reach

Figure 17. Low Forward Reach

* Three outliers removed from IDEA Center data due to data translation errors in software

Figure 18. Upper Side Reach

Figure 19. Low Side Reach

Note:  3 outliers removed from IDEA Center – Protocol data due to translation errors in software

For the IDEA results, the forward reach graph represents reach over the anterior most (forward) point of the wheelchair or body for trials with no weight lifted (as in Fig. 14-15). We do not know how forward reach was measured in the UDI study. In the BS8300 study, trials were conducted over a counter and it is not known whether the results reported represent highest reach for each person in general or over the anterior most point. It is also not clear who was excluded or included in the UDI and BS8300 results.

The 5^th percentile values for high forward reach in both the IDEA and UDI studies are well below the current U.S., Australian and Canadian standard of 1220 mm (48 in.). The reason for the very low 5^th percentile and minimum values in the IDEA study is that several individuals’ reach envelope only intersected the anterior most plane at the extended part of their reach envelope (near the bottom of the arch). They could reach higher but only behind the anterior most plane, e.g. if they had knee space in which to pull their device. This may be true of other studies as well but information is not available to understand what is meant by highest reach. 

The UDI and IDEA results are remarkably similar given that there are so many ways that reach can be measured. The results indicate that there are some people at the lower tail end of the distributions who have very restrictive reaching ability. The minimum value for the BS8300 research (the only one reported) was close to the current standards. We believe that this is due to either a different measurement technique (highest reach regardless of whether it was behind the anterior most point) or exclusion of individuals in the sample who could not reach to the anterior most point.

High side reach results have a similar pattern although the BS8300 study results were lower than the standards of the other countries. The BS8300 and the UDI results for low side reach were within 100 mm (4 in.) of each other at the minimum end of the range. The participants in the IDEA sample with the most restricted reach ranges were not allowed to reach lower, however, due to the safety considerations imposed.

The reach results for the different studies demonstrate great differences, even though some consistent trends are evident. More information is needed to clarify exactly how the UDI and BS8300 reach studies were completed, how the data in each was analyzed, and who the people with extreme values were. The UDI data may include some outliers that need to be identified and eliminated. The BS8300 study may have excluded people whose reaching ability may be more restricted than those included by the UDI and IDEA center.

The reach results for the different studies demonstrate great differences even though some consistent findings emerged. More information is needed to clarify exactly how the UDI and BS8300 reach studies were completed and how the data in each was analyzed. More detailed information is needed about the people at the extremes in reaching in both studies. The UDI data may include some outliers that need to be identified and eliminated. The BS8300 study may have excluded people whose reaching ability may be more restricted than those included by the UDI and IDEA center. The IDEA Center results demonstrate that some individuals can only reach the anterior or lateral most plane at the extreme of their reach range. Additional analyses, removing individuals whose forward or side reach range is restricted in this way may result in more comparable findings.

Thus, standards should reflect the most functional reaching approach. Besides free reaching ability, there are additional exclusion criteria that could be imposed for the purpose of establishing standards, for example, the ability to lift an object or perform a grasping task. The IDEA Center studied the impact of grasping and lifting a weight during a task. The standards make no mention of the task so those results are not presented here. These data may perhaps be more relevant for developing standards since they are more realistic tasks. Our preliminary analyses of the weighted reach trial data indicate that many of the participants with marginal reaching abilities would be eliminated from an analysis of these trials because they could not perform the task at all (even with the aid of an assistive device called a “cuff” that eliminates the need to grasp the object). The remaining participants are likely to have more extensive reach envelopes and thus the low end of the range could actually be higher than with free reach simply due to exclusion of people with marginal reaching abilities. Our preliminary analysis also indicates that many participants could reach higher at a 45 degree angle than forward or to the side. Thus, this set of trials may provide information for changing the approach used in the standards. Individuals are likely to use the approach that is most functional for them, if there is enough room.

Currently the U.S., Canadian and Australian standards address reach over an obstruction in a very simplistic manner. They specify maximum and minimum heights but do not take into consideration the fact that the depth and height of the obstruction can vary with a corresponding impact on the reach envelope. Reaching over an obstruction was studied in the BS8300 study, and, the limits of obstructed reach can be derived from the IDEA data. But, since there are so many variables that have an effect on reach over obstructions, e.g. knee space depth, armrest height, depth of obstruction, height of obstruction, etc. it is not easy to devise a means to represent it in a way that is useful for designers. The BS8300 approach included different requirements for different scenarios. This seems to offer a promising direction for improving this aspect of accessibility standards.