ACCESS BOARD RESEARCH

Requirements for Power Mobility Aids

November 15, 1995

Prepared by:
KRW Incorporated
1008 Pendleton Street
Alexandria, Virginia 22314

CONTENTS

• ACKNOWLEDGMENT
• EXECUTIVE SUMMARY
• 1. INTRODUCTION
• 2. BACKGROUND
• 3. STUDY METHODOLOGY
• 4. ANALYSIS AND RECOMMENDATIONS
• 5. ADDITIONAL RECOMMENDATIONS
• TECHNICAL ARTICLE
• SELECTED BIBLIOGRAPHY
• MANUFACTURERS

ACKNOWLEDGMENT

KRW would like to express appreciation to the many individuals and organizations who contributed to the conduct of the research presented in this report. In particular, we are grateful to James Pecht, Laurinda Steele Lacey, David Yanchulis and the other Access Board staff for their technical insight and assistance.

Katherine Hunter-Zaworski of the Transportation Research Institute at Oregon State University provided valuable analytical support as did KRW staff members Patricia Ohleger and George Leonard. Craig Gates' expertise with AutoCAD and Mannequin software packages was invaluable in allowing the team to work through the many iterations of spaces and human figures needed during the modeling and analysis phases of the project.

We would also like to acknowledge the assistance provided by wheelchair and scooter manufacturers too numerous to list who, early in the project, responded to our mail survey, requesting chair and scooter dimensions and later allowed us to take measurements and "test drive" their power chairs and scooters through T- and 360 degree-turning tests.

We are also appreciative of the information provided by Lee Norrgard of the American Association of Retired Persons from an early draft report describing a scooter evaluation study that was useful in confirming our analysis concerning clear spaces for scooters.

EXECUTIVE SUMMARY

The Americans with disabilities Act Accessibility Guidelines (ADAAG) dealing with wheelchair access were written for manual wheelchairs. Because the specifications and operating characteristics for motorized wheelchairs and for three- and four-wheeled scooters are substantially different than for manual wheelchairs, information is needed so that the Access Board can assess whether the current ADAAG standards provide an acceptable level of access to the built environment for persons using these power mobility devices.

The approach used in making this assessment was to collect product information for powered mobility aids, compile and review related literature pertaining to previous research, studies and technical information, and develop an anthropometric model which would provide a range of adult body sizes and a sample representation of the average adult population in the United States. These three elements, the product information, literature review information, and anthropometric model, were used to perform analyses to assess whether the current standards provide an acceptable level of access for persons using power mobility devices. If current ADAAG spaces were not accessible, alternative solutions are provided.

In our review of current product data for power mobility devices, we collected dimensional information to evaluate current ADAAG requirements for clear floor space and maneuvering clearances, which are primarily a function of wheelbase length and width, turning radius, front and rear extensions and total chair width and length. Reach range is a function of seat height and seat position and the physical characteristics of the individual seated in the mobility aid. Therefore, we collected data on those design parameters to model reach ranges.

In our review of previous wheelchair and scooter studies, we searched for information on the clear floor space, maneuvering clearances, and reach ranges for power wheelchairs, three- and four-wheeled scooters and related research concerned with the users of these mobility aids. In particular, we were sensitive to studies which described the tailoring of wheelchairs to the specific needs of individuals to gain insight into the unique requirements of these individuals with respect to reach ranges. Parametric data concerning both front and side approach reach ranges was compiled from numerous sources including a survey of manufacturers, comparative studies published in trade and consumer periodicals, and KRW field measurements. For side approach analysis, we collected information on seat height and placement and wheel chair width. For front approach analysis, we collected information on seat height and placement, and the front profile of the mobility devices.

In performing our analysis, we developed scaled drawings using computer aided drawing software of the applicable spaces of the ADAAG standards, as the "operating envelope" against which the parametric data for power mobility devices could be assessed to determine if they "fit" within the

ADAAG clear spaces and maneuvering clearance specifications. To perform our analysis of reach ranges we used a combination of seat height, seat position, and anthropometric data. In the absence of verifiable data on the anthropometrics of the disabled population in the U.S. we modeled using the 95th percentile of the U.S. adult male and the 5th percentile of the U.S. adult female. The results of each of the above were averaged to yield dimensions for the average U.S. adult. Our model used the human figure animation software Mannequin to determine if the powered mobility aids and the average U.S. adult could reach the high and low points from the power mobility aids. Those ADAAG defined spaces which could not be successfully navigated were identified as being candidates for clarification or revision to accommodate power mobility devices.

1. INTRODUCTION

The Americans with Disabilities Act (ADA) of 1990 provides comprehensive civil rights protections to individuals with disabilities in the areas of employment, State and local government services, transportation services provided to the public, public accommodations, commercial facilities, and telecommunications. The ADA requires that buildings and facilities be readily accessible to and usable by individuals with disabilities in the case of new construction or alteration. The U.S. Architectural and Transportation Barriers Compliance Board (Access Board) is responsible under the ADA for developing minimum guidelines for buildings and facilities. With this in mind, the Access Board published the ADA Accessibility Guidelines (ADAAG) for Buildings and Facilities.

The Access Board has always intended ADAAG to be a "living document," and therefore, the guidelines undergo periodic review to allow for revisions based on new designs and technologies which provide for greater accessibility to people with disabilities. To this end, the Access Board developed a proposed research agenda that included recommendations for research into the adequacy of the clear floor space, maneuvering clearances, and reach ranges for power mobility devices. Existing ADAAG requirements for maneuvering clearances assume that the person is using a manual wheelchair. The larger dimensions and diverse operating parameters of power wheelchairs and scooters could restrict access to certain elements such as fixed tables, lavatories, and drinking fountains. They may also prevent an individual from approaching certain elements such as telephones and controls as closely as could be achieved using a manual wheelchair.

Because research on clear floor space, maneuvering clearances, and reach ranges has been based primarily on manual wheelchairs and their users, and there is growing use of power mobility devices, the Access Board contracted with KRW to conduct an eight-month research project to study the relationship between the current requirements of ADAAG and the physical dimensions and operating parameters of power wheelchairs and scooters. The findings and recommendations of this project will allow the Board to determine the impact of the ADAAG standard on the growing population of power wheelchair, three-wheeled and four-wheeled scooter users and whether current standards provide an acceptable level of access to the built environment for persons using these mobility devices.

2. BACKGROUND

The clear floor space, maneuvering clearance, and reach range specifications in the ADAAG are based largely on accessibility research conducted using manual wheelchairs. The operating characteristics of wheelchairs, both manual and powered, and scooters have changed significantly since those early studies. The demographic and anthropometric characteristics of the population of wheeled mobility aid users have also changed. The ADAAG needs to be reexamined with respect to the current generation of powered mobility aids and the broader population that uses them. Consideration should be given to modifying or clarifying the accessibility guidelines where appropriate to reflect the changes in the operating parameters of the current generation of mobility devices and their users.

3.STUDY METHODOLOGY

3.1 Data Collection

The operating requirements for clear floor space, maneuvering clearances and reach ranges for powered mobility devices were identified through a line-by-line review of ADAAG specifications. Computer aided drawings (CAD) of each requirement were developed for each of the 44 applicable requirements identified. 

Data on the size and operating characteristics of power chairs and scooters was initially collected from two sources. A survey questionnaire was developed and mailed to manufacturers to collect data on the size and operating characteristics of power chairs and scooters and their market share. At the same time the manufacturer survey was being conducted, a literature search was performed to identify both relevant wheelchair and scooter research and comparative data for the numerous models of power chairs and scooters.

Of the 45 survey questionnaires mailed to manufacturers, 23 responses were received. Much of the data requested on the questionnaire was not provided. Follow-up telephone calls were made to collect missing or obviously incorrect information with limited success in reaching non-respondents or completing incomplete surveys.

The data on power chairs and scooters found in the literature survey was compared with the data provided by manufacturers responding to our mail survey. Because of the large disparity in the data from the two sources, it was decided that field measurements were needed to reconcile the data received from manufacturers and cited in the literature.

Field measurement forms and procedures were designed to standardize the collection of measurements. The protocol for taking measurements utilized the surface the mobility device was rested on as the horizontal baseline from which height measurements were taken. A vertical baseline was established using a plumb line from the outermost front part of the scooter or power chair. This vertical baseline was established using a 3-foot carpenters level in the plumb position touching the front most part of the chair or scooter. The vertical baseline was then used as the base from which horizontal measurements were taken.

The procedure and forms were evaluated and refined in the course of several trips to local powered mobility device vendors. Most of the physical measurements of power chairs and scooters included in our test population were obtained at an accessibility equipment exposition in Florida, and additional measurements were made during visits to vendors in the Washington D.C. metropolitan area. The test population includes device measurements for 27 power wheelchairs and 36 scooters. Though difficult to estimate, the wheelchair data represents approximately 95 percent of the chairs in use. Because the variety and number of scooters being manufactured is so variable, estimates of the market share of scooter models is even more difficult. However, based on their presence at the trade shows visited and the models available from vendors and medical retailers visited, we are confident that our data covers in excess of 90% of the scooters is use.

The field measurements were analyzed and compared with the data obtained from published comparative studies and provided by manufacturers responding to our mail survey. The major inconsistency noted was the difference between the large number of models reported by the manufacturers and the more limited number available from vendors. During site visits to collect field measurements, manufacturers' representatives typically indicated that their floor models were current models and that they represented their largest base of sales. When the data obtained from the field was compared to that derived from comparative studies and that supplied by manufacturers, there were differences in the measurements and operating parameters from the two sources. Many of the models described in comparative studies had been discontinued. Some of the manufacturers had merged while others had gone out of business. Further, new manufacturers and new models had entered the market.

Based on discussions with manufacturers' representatives, we concluded that the powered mobility aid market, especially the scooter market, is so dynamic that it would be difficult to document the specifications and operating parameters in a consistent fashion for all of the models presently available. In light of the variability of the number of manufacturers and models of power mobility devices, we undertook a further evaluation of the data. An analysis of the specifications and operating parameters from the three sources was conducted to identify the most critical parameters needed to analyze clear floor spaces, maneuvering clearance and reach ranges. The parameters identified were overall length, overall width, wheelbase length, seat height and seat position.

These parameters were selected for two primary reasons: (1) They are the basic parameters needed to analyze clear spaces, maneuvering clearances and reach ranges, and (2) They require no base line, e.g., the overall length and width are an out-to-out measurement of the longest and widest part of the chair or scooter. Further, the wheelbase length is normally the center of the front wheel to the center of the back wheel. The seat height and seat position is a dimension that can vary significantly depending on how it is measured.

A comparative matrix was developed to analyze these parameters for each of the models of power chairs and scooters. The dimensions provided by manufacturers, those cited in the literature, and our field measurements were logged for each parameter for each model. The matrix served two purposes. First, it visually demonstrated the voids and inconsistencies in the data from the research, comparative studies and data supplied by the manufacturers. And second, it facilitated the analysis of operating parameters, e.g., it allowed us to evaluate the consistency of the data among the three sources. Where there was little consistency, we then determined how best to use the available data in our modeling process. Analysis of the data supported our earlier observations:

• There is considerable variation between the number of models listed in the literature and that reported by the manufacturers.
• There is considerable variation in the dimensions and operating parameters provided by manufacturers, in the literature, and in our field measurements, even on parameters that are easily measured.
• Data distilled from the literature and provided by the manufacturers, when available for a specific model, seldom correlated exactly with our field measurements.

The above observations are important because they point out a major issue with respect to research of the nature conducted by this project. There needs to be a standard procedure for measuring and reporting dimensions and operating parameters for mobility devices. If future research is to benefit from this effort and others like it, then each must be able to build and expand upon the efforts that precede it. In the absence of a standard procedure for measuring and reporting specifications for power chairs and scooters, the proliferation of incomparable data will likely continue and the validity of data available for use by the public, device users and the standard setting agencies will continue to be questionable.

We next analyzed the data in the matrices to determine how it could be used to study clear spaces, maneuvering clearance and reach ranges in a way that the disparities in the data could be accounted for. Overall length and overall width from all reported sources for all models were used in our analysis of clear spaces. For maneuvering clearances the wheelbase length, overall width and overall length were used. Dimensional data from the field measurements that located the seat heights and positions for the power chairs and scooters was used as the basis for the analysis of reach ranges. The methodologies used in our analysis are described in detail in the analysis and recommendation section of this report.

3.2 Anthropometric Model

The model used to evaluate the reach ranges for power chairs and scooters has two components: (1) A human figure in a seated position which can be adjusted to simulate different seat positions for mobility devices, and (2) Sectional views of specific ADAAG spaces that permit analysis of reach ranges. The ergonomic drawing and design software, Mannequin, Release 1.1, was used to model the human figure in a seated position representing the average U.S. adult.

The Mannequin software models human figures in scaled settings and is the standard in the legal profession in modeling accident and crime scenes. The firm which developed and sells Mannequin, Biomechanics Corporation of America (BCA), purports to have made extensive efforts to ensure that their data base of anthropometric data is representative of the human population. BCA cites 10 sources as references for its anthropometric data. Among those cited are works frequently cited in the literature as basic references for anthropometric design data and include:

• Humanscale 1/2/3 and 4/5/6,Diffrient, A.R. Tilley and D. Harman (Eds.), Dreyfuss Associates, Cambridge, Mass; MIT Press, 1981
• Anthropometrics Sourcebook. Edited by Webb Associates,Volume 1: Anthropometry for Designers, NASA Reference Publication 1024. 1978
• Bodyspace Anthropometry, Ergonomics and Design, Pheasant, Stephen Taylor and Francis, 1986

Mannequin allows the user to model a human figure based on: sex (male or female); percentile of the population (2.5%, 5%, 50%, 95%, and 97.5%); body style (heavy, average, and thin); age (adult or child); country of origin (ten options including U.S.A.); and figure type (human, robot, and stick). The parameters used from these options were: male, 95th percentile, average body type, adult, U.S.A., human figure; and female, 5th percentile, average body type, adult, U.S.A., human figure. The average of these two options yields the average U.S. adult human figure. 

The Mannequin software permitted us to configure the human figure in various seated positions needed to model a person using a power chair or scooter. We were able to manipulate figures to sit, bend forward and to the side and reach in an anthropometrically correct manner. The software incorporates 3D drafting capabilities, including dimensioning, rotation, and scaling. The scaling feature was particularly important. The scale used in our CAD drawings was matched precisely to that of the human figure created by Mannequin.

Modeling of ADAAG spaces was accomplished using AutoCAD, Release 12, by Autodesk. AutoCAD is a general purpose computer aided design (CAD) program for preparing two-dimensional drawings and three-dimensional models. Forty-four space drawings, taken from the ADA Accessibility Guidelines, were drawn using the AutoCAD software. Nine of these drawings were needed to study reach ranges. The software allowed us to import Mannequin-generated seated figures for selected power chair and scooter parameters to evaluate ADAAG reach ranges.

3.3 Reach Ranges

Our reach range modeling process for power chairs and scooters took into account the range of data collected from the three sources (literature, manufacturers, field measurements) cited earlier and established a minimum and maximum envelope for all of the devices for which data was collected. Critical dimensions for reach range analysis are: (1) seat height measured from the floor; (2) position of the seat relative to the overall width of the chair/scooter for side reach; and (3) position of the seat relative to the front most part on the power chair or scooter that touches a wall or a vertical plane, e.g., the part at the extreme front of the power chair or scooter for front reach.

Using these dimensions, a seat position point was defined which corresponded to a point on the computerized mannequin's body. After the seat position point of a chair or scooter was known or determined, the mannequin figure was then placed in a sitting position according to that point.

The following sections describe the methodology used in the analysis of front and side approach reach ranges.

3.3.1 Front Approach

Dimension data for power chairs and scooters from all sources was reviewed and used to tabulate the range of seat positions for a front approach. Seat position was defined as the point where a vertical line running down the seat back intersects a horizontal line running along the surface of the seat. This seat position point was used as the reference point to place the mannequin model in the chair. Exhibit 2, Seat Position The male mannequin figure was placed on this seat position point with the legs positioned at a 90 angle.

Seat position points for all of the power chair and scooter models were tabulated. Seat heights were measured from the floor to the point at which the top of the seat intersects the back of the seat. Seat distances were measured from a vertical plane (wall) at the front most portion of the power chair or scooter, to the seat back at a point at which the seat back intersects the seat cushion surface.

These seat position points were reviewed and the four extreme points were identified for power chairs and scooters. These four extreme points are:

A = highest from the floor/closest to the wall

B = highest from the floor/farthest from the wall

C = lowest from the floor/closest to the wall

D = lowest from the floor/farthest from the wall

An envelope for power chairs and an envelope for scooters was plotted using the extreme seat position points for the power chairs and scooters. These points represent the maximum/minimum seat positions from the floor and the wall.  Points A, B, C, and D define the envelope that encompasses the possible seat positions for power chairs. A similar envelope was developed for scooters.

Using the points A, B, C, and D as the extreme seat position points, the mannequin figure was seated in an upright position at each of the extreme seat positions. The mannequin was then manipulated to define a forward reach arc identifying the high and low forward reach points on the wall at each of the extreme seat position points.

If the mannequin, when seated in an upright position, could not touch the high and low point on the wall from each of the points A,B,C, and D defining the seat position envelope, it was then configured in a leaning position until it could touch the points on the wall. The mannequin's positions were limited by the wall and the floor. For example, the mannequin could be manipulated to lean over until its head touched the wall. If the mannequin's feet penetrated the floor it was moved upward, if the knees penetrated the wall, it was moved back away from the wall.

This manipulation was continued until it was determined if the mannequin could touch the high and low points on the wall at each location which defined the seat position envelope or until a new more restrictive seat position envelope was defined.

The procedure was followed with figures representing the 95th percentile male mannequin and 5th percentile female mannequin. Seat position envelopes were defined for both and then an average seat position envelope was calculated. This average seat position envelope was used to determine the number of power chairs and scooters that have design parameters that fall within this envelope of attainable forward reach.

3.3.2 Side Approach

A similar procedure was used to model side approach reach ranges for power chairs and scooters. From the dimension data collected, overall widths of the power chairs and scooters were arrayed to identify the narrowest and widest devices. Overall width is the out-to-out distance between the extreme parts on each side of the device. The range of seat heights for scooters and power chairs was also identified.

For side approach seat position was defined as the point where a vertical line down the center line of the seat back intersects a horizontal line along the surface of the seat. This seat position point was used as the reference point for placement of the mannequin model in the seat. The 5th percentile female mannequin was seated in the chair.

The various seat heights were arrayed and the maximum seat height (greatest distance from the surface of the seat to the floor) and the minimum seat height (smallest distance from the surface of the seat to the floor) were determined for all of the devices. With the device positioned parallel to a vertical wall and touching the wall, the minimum and maximum distance from the wall to the centerline of the seat were also identified (these distances represented the narrowest and widest power devices). From these seat positions, an envelope was defined for the devices describing the extreme seat positions from the floor and wall. The points are defined as follows:

A = highest from the floor/closest to the wall

B = highest from the floor/farthest from the wall

C = lowest from the floor/closest to the wall

D = lowest from the floor/farthest from the wall

The center line of the chair was determined by dividing the overall width by two. A vertical line was drawn 10 inches from and parallel to the wall. This line or plane is the closest the wheelchair was allowed to approach the wall. Thus, this line, 10 inches away from the wall, was the reference line from which the wheelchair offsets were measured. Once plotted, points A,B,C and D defined the envelope for all of the seat positions for power chairs. A similar envelope was defined for scooters.

The side approach positions for the mannequin figures representing the 95th percentile male and 5th percentile female were then evaluated to determine if the high and low side approach reach points could be touched from the extreme seat position points, or if there was a need to redefine the seat position envelopes for power chairs and scooters. The seat position envelopes for the 95th percentile male and 5th percentile female were averaged to determine the seat position envelopes for the average U.S. adult.

3.4 Reach Over Obstructions

The profiles of the scooter tillers were plotted for each scooter in our test population. The tillers were measured in the upright position from the front most part of the scooter. Similar profiles were plotted for the power chairs. These profiles included the controller if it extended above or beyond the chair arm rest. These profiles were used to determine how close the scooters and chairs could approach an obstruction with a forward approach. The mannequin was positioned in each of the four seat position points that describe the seat position envelope. If the mannequin's finger tips could reach the "touch point" beyond the obstruction, then the envelope remained as it had been defined for the original reach ranges. A new seat position envelope was defined if the mannequin had to be moved to reach the "touch point". The result of this analysis was a redefined seat position envelope for each of the seven ADAAG configurations that require reach over an obstruction. The seat position envelopes for each of the seven ADAAG configurations were graphically plotted and then the seat position points for the chairs and the scooters were plotted to determine how many of the chair and scooter seat position points fell within the seat position envelope for a particular configuration. If all of the chair and scooter seat position points were inside the seat position envelope for a particular obstruction the ADAAG standard was considered appropriate.

3.5 Turning Radius

3.5.1 Power Chairs

The distance between the center point of the front wheels to the center point of the rear wheels was measured. This measurement was compared to distances reported in the literature and from the data provided by manufacturers. The majority of power chairs have the ability to turn on their own wheelbase. One back wheel is capable of tracking backwards as the power chair turns in a circle, thus the chair can actually turn in a circle with a diameter less than its wheelbase.

3.5.2 Scooters

Most scooters do not have the capability to turn on their own wheelbase because one rear wheel cannot be locked or made to track backward. Further, most of the front wheels on scooters do not turn to a 90 angle. Data from the manufacturers and data obtained from the literature on turning radius varied considerably from the data we obtained from actual observations and measurements. A recent study on scooters sponsored by the American Association of Retired Persons conducted turning radius and T-turn around tests on 15 of the most popular scooters. These results are compared to our observations and measurements in the analysis section of this report.

3.6 Clear Spaces and Maneuvering Clearances

A list of the ADAAG spaces tested for clear space and maneuvering clearance follows.

Clear Floor Space and Maneuvering Clearance Drawings

Graphic analysis was used to evaluate the operating parameters of the devices in the ADAAG spaces. The ADAAG spaces were drawn to scale on CAD and a box drawn to the same scale was used to graphically model the length and width of each chair and scooter in the test population. The longest and widest power chair and the longest and widest scooter were tested in the spaces to determine how many of the spaces could accommodate these largest mobility aids. After it was determined that many of the spaces were too small, the power chairs and scooters were ranked by size. Because length was the dimension that varied the most, the overall length was used as the primary ranking factor, and overall width was the secondary factor. Thus, if there were four scooters that had overall lengths of 48 inches, those four were then ranked by overall width. Once these rankings were completed for power chairs and scooters, they were graphically tested in rank order in all of the spaces until a power chair and a scooter was found that could fit into and maneuver within each or most of the spaces. If the power chair or the scooter did not fit into a space, that space was identified for possible modification.

4. ANALYSIS AND RECOMMENDATIONS

Wheeled mobility aids are prescriptive devices that facilitate mobility for persons with disabilities. Individuals are unique in their needs and devices are tailored or designed to meet those unique needs. The wheeled mobility aid market reflects the diversity of individuals who use them. There are numerous styles and models and within these styles and models there are wide variations in dimensions. The results of the literature search, survey and analysis of dimensions reflect this diversity. To add to this variability, new designs and models are constantly entering the marketplace.

Because of the dynamics of the power mobility device marketplace, our analysis methodology was designed to identify the current ADAAG standards or spaces that should be considered for modification to accommodate most of the power chairs and scooters that are being manufactured.

Scooters present even greater diversity than power chairs in terms of their size and operating characteristics. The scooter measurements taken from our test population include those for small, highly maneuverable devices to large, golf cart-like vehicles that are designed for outdoor use. Further, the measurement data and operating characteristics information provided by manufacturers was developed without the benefit of the ANSI standards generally used by wheelchair manufacturers.

4.1 Reach Ranges

The analysis conducted on reach ranges and the reach over obstructions yielded specific seat position envelopes. These seat position envelopes defined minimum and maximum limits for seat positions from which the average U.S. adult could reach the high and low touch point or a specified touch point. If a specific model of a power mobility aid was found to have a seat position that fell within the seat position envelope, then an average U.S. adult seated on that device could reach the ADAAG prescribed touch points.

The following sections summarize the analysis conducted to evaluate front and side approach reach ranges and the reach over obstructions for power chairs and scooters.

4.2 Front Approach

4.2.1 Front Approach Power Chairs

The seat position envelope for front approach, power chairs was determined to be:

• High/Close: 30"/25¼"
• High/Far: 30"/34½"
• Low/Close: 11"/25¼"
• Low/Far: 11"/34½"

This envelope was determined by plotting all of the seat position points for all of the power chairs in our test population.

The above seat position envelope had to be reduced to allow both the 95th percentile male and 5th percentile female to touch the high 48-inch and low 15-inch points for front approach. The following table shows those seat position points where the 95th percentile male and the 5th percentile female are able to touch both the high (48-inch) and low (15-inch) points. The average of the two was calculated to determine the seat position envelope for the average U.S. adult. Thus, if the seat position point of a power chair falls within this seat position envelope, the average U.S. adult will be able to touch the high point (48-inches) and low point (15-inches).

Front Approach Power Chairs
Average of 95% Male and 5% Female Seat Position Point Envelope (Inches)

Front approach seat position points for all of the power chairs were plotted to determine how many of the power chairs had seat positions that would fall within the average seat position envelope shown in the above table. Four of the chairs fell outside of the envelope for front approach which means 76.47% of the power chairs surveyed fell within the envelope.

4.2.2 Front Approach Scooters

The envelope for the front approach seat position for scooters was determined to be:

• High/Close : 29"/26½"
• High/Far: 29"/49½"
• Low/Close: 12"/26½"
• Low/Far: 12"/49½"

This envelope was determined by plotting all of the seat position points for all the scooters we were able to collect data on.

The above seat position envelope had to be reduced to allow both the 95th percentile male and 5th percentile female to touch the high 48-inch and low 15-inch points for front approach. The following table shows those seat position points where the 95th percentile male and the 5th percentile female are able to touch both the high (48-inch) and the low (15-inch) points. The average of the two was calculated to determine the seat position envelope for the average U.S. adult. Thus, if the seat position point of a scooter falls within this seat position envelope, the average U.S. adult will be able to touch the high point (48-inches) and low point (15-inches).

Front Approach Scooters
Average of 95% Male and 5% Female Seat Position Point Envelope (Inches)

Front approach seat position points for all of the scooters were plotted to determine how many of the scooters surveyed had seat position points that would fall within the average seat position envelope shown in the above table. Only six of the twenty-two scooter models had seat points that fell within the envelope. This is 27.2% of the scooters surveyed.

4.2.3 Recommendation: Front Approach Reach Range

Based on the above findings and with the understanding that many of the scooters have seats that can rotate which allows a side approach on the scooter and then the seat is rotated to a forward approach position, it is recommended that the high forward reach of 48-inches and the low forward reach of 15-inches remain as specified.

4.3 Side Approach

4.3.1 Side Approach Power Chairs

The envelope for the side approach seat position for power chairs was determined to be:

• High/Close : 30"/11¾" + 10"
• High/Far: 30"/13½" + 10"
• Low/Close: 11"/11¾" + 10"
• Low/Far: 11"/13½" + 10"

This envelope was determined by plotting all of the seat position points for all the power chairs we were able to collect data on.

The above seat position envelope had to be reduced to allow both the 95th percentile male and the 5th percentile female to touch the high (54-inch) and low (9-inch) points for side approach. The following table shows those seat position points where the 95th percentile male and the 5th percentile female are able to touch both the high and the low points. The average of the two was calculated to determine seat position envelope for the average U.S. adult. Thus, if the seat position point of a power chair falls within this seat position envelope, the average U.S. adult will be able to touch the high point (54-inches) and low point (9-inches).

Side Approach Power Chairs
Average of 95% Male and 5% Female Seat Position Point Envelope (Inches)

Side approach seat position points for all of the power chairs were plotted to determine how many of the chairs surveyed had seat position points that would fall within the average seat position envelope shown in the above table. All but one of the power chairs surveyed fell within the envelope. Thus 93.75% of the power chairs fell within the side reach envelope.

4.3.2 Side Approach Scooters

The envelope for the side approach seat position for scooters was determined to be:

• High/Close : 29"/9¾" + 10"
• High/Far: 29"/14" + 10"
• Low/Close: 12"/9¾" + 10"
• Low/Far: 12"/14" + 10"

This envelope was determined by plotting all of the seat position points for all the scooters we were able to collect data on.

The above seat position envelope had to be modified to allow the 95th percentile male to touch the high (54-inch) and low (9-inch) points for side approach. One point had to be modified further for the 5th percentile female. The following table shows those seat position points where the 95th percentile male and the 5th percentile female are able to touch both the high (54-inch) and the low (9-inch) points. The average of the two was calculated to determine the seat position envelope for the average U.S. adult. Thus, if the seat position point of a scooter falls within this seat position envelope, the average U.S. adult will be able to touch the high point (54-inches) and the low point (9-inches).

Side Approach Scooters
Average of 95% Male and 5% Female Seat Position Point Envelope (Inches)

Side approach seat position points for all of the scooters were plotted to determine how many of the scooters surveyed had seat position points that would fall within the average seat position envelope shown in the above table. Three of the twenty-two scooter models tested had seat position points that fell completely outside of the average envelope. Twelve models had high seat position points that fell outside of the envelope, but these same twelve scooters had low seat position points that fell well inside the average envelope. Thus only the three models that had seat position points that fell completely outside of the envelope were considered. Thus, 88% of the scooters surveyed fell within the average envelope.

4.3.3 Recommendation: Side Approach Reach Range

Because the majority of power chairs and scooters had seat position points that fell within the average envelope, it is recommended that the high side approach reach of 54-inches and the low side approach reach of 9-inches remain as specified.

4.4 Reach Over Obstructions

Seven ADAAG configurations require the users to reach over an obstruction to touch a specified point. The seven configurations are:

• Front approach 25-inch counter with touch point at 44-inches above the floor.
• Front approach 20-inch counter with touch point at 48-inches above the floor.
• Front approach drinking fountain.
• Front approach table with 36-inch clear area for approach and a touch point at 27-inches above the floor.
• Side approach 34-inch x 24-inch cabinet with a touch point at 46-inches above the floor.
• Side approach shelves.
• Side approach clothes hanger.

4.5 Front Approach: 25-inch Counter

The parameters for the analysis of the reach over this obstruction for front approach are shown below. A scaled drawing is in Appendix A (Drawing No. 36). The obstruction is a 25-inch counter at a height of 34 inches from the floor. A point at 44 inches above the floor on the wall over the counter is the touch point.

4.5.1 Power Chairs

Our analysis indicated that all parts of the power chairs in our test population fit beneath the counter. For the 95% male mannequin, the seat envelope had to be modified for the upright figure to touch the point 44 inches up the wall. For the 5% female mannequin, the seat envelope had to be modified for the maximum leaning figure to touch the point 44 inches up the wall.

The following table compares the front approach seat position envelope for power chairs, with the seat position envelope for the 25-inch counter obstruction for the average U.S. adult.

In analyzing the above seat position envelopes for power chairs, none of the seat position points for the chairs fall within the seat position envelope for this obstruction. Based on this analysis, it appears that few, if any, of the power chairs would fall within this restricted envelope.

4.5.2 Scooters

A seat position envelope for the average U.S. adult could not be calculated for scooters. The 5th percentile female could not touch a point at 44 inches on the wall, because the tillers on the scooters moved the seat position for scooters too far away from the wall. The female mannequin figure was simply too small to reach the point on the wall at 44 inches above the floor.

4.5.3 Recommendation: 25-inch Counter

A forward reach over a counter is shown in ADAAG Figure 5(b), Maximum Forward Reach Over an Obstruction for: 25-inch counter, with X=25-inches, Y=44-inches and Z=25-inches. Because there was a very limited range of seat positions for power chairs that could be found where the average U.S. adult could reach over this obstruction and because the 5th percentile female could not reach this obstruction from any of the scooter seat positions, it is recommended that explanatory notes be added to ADAAG Figure 5(b) as follows:

The 25-inch counter will be an obstruction to individuals in most power wheel chairs and scooters and will not permit them to touch a point on the wall 44-inches up from the floor. Scooter users may be able to access the counter from a parallel approach if sufficient space is provided and their scooter seat will swivel 90 degrees allowing them to reach from the side of the scooter.

It is further recommended that human testing be conducted to determine the appropriate height of the touch point on the wall behind the counter before any revisions are made to this standard.

4.6 Front Approach: 20-Inch Counter

The parameters for the analysis of the reach over an obstruction are based on the obstruction of a 20-inch counter at a height of 34 inches from the floor. A point at 48 inches above the floor on the wall over the counter is the touch point.

4.6.1 Power Chairs

All parts of the power chairs in our test population fit beneath the counter. For the 95% male mannequin, the seat envelope must be modified for the upright mannequin to touch the point on the wall. When placed in a low/far seat position, the mannequin can touch the point 48 inches up on the wall. All other seat positions require modification of the envelope for the figure to touch the point. For the 5% female mannequin, the seat envelope must be modified significantly for the female mannequin to touch the point 48 inches up on the wall.

The following table compares the front approach seat position envelope for power chairs, with the seat position envelope for the 20-inch counter obstruction for the average U.S. adult.

In analyzing the above seat position envelope for power chairs, ten of the seventeen power chair seat positions tested fall within the seat position envelope. This equates to 58.5% of the power chairs.

4.6.2 Scooters

A seat position envelope for the average U.S. adult could not be calculated for scooters. The 5th percentile female could not touch a point at 48 inches on the wall, because the tillers on the scooters moved the seat position for scooters too far away from the wall. The female mannequin figure was simply too small to reach over the obstruction to a point on the wall 48 inches above the floor.

4.6.3 Recommendation: 20-inch Counter

This counter is shown in ADAAG Figure 5(b) (see above), Maximum Forward Reach Over an Obstruction for: 20-inch counter, with X=20-inches, Y=48-inches and Z=20-inches. Because over one half of the possible seat positions for power chairs are such that the user can reach over this obstruction and touch a point 48 inches above the floor on the wall and because the 5th percentile female cannot reach this obstruction from any of the scooters using a forward approach, it is recommended that explanatory notes be added to ADAAG Figure 5(b) as follows:

If a scooter user can parallel approach this counter and rotate the seat 90 degrees to a forward approach position most scooter users could reach over this obstruction. Many users of power chairs should be able to reach over this counter and touch a point on the wall that is 48-inches up from the floor.

It is further recommended that human testing be conducted to determine the appropriate height of the touch point on the wall behind the counter before any revisions are made to this standard.

4.7 Front Approach: Drinking Fountain

The forward most control point on power chairs that must be considered in the analysis of drinking fountain clearance is the arm rest or control box. This measurement was taken at an average height of 27 inches from the floor and shifts the seat position envelope for forward approach analysis away from the wall an additional 8 inches. For scooters, the tiller hits the obstruction at 33 inches above the floor, thus shifting the seat position envelope 17 inches further from the wall.

4.7.1 Power Chairs

For the 95% male mannequin, the seat position envelope for power chairs had to be modified because the knees of the mannequin hit the fountain at all seat positions except the low/far position. For the 5% female mannequin, the seat envelope had to be modified because the knees of the mannequin hit the drinking fountain in the high and forward seat positions.

The following table compares the front approach seat position envelope for power chairs (shifted 8 inches further from the wall), with the seat position envelope for the drinking fountain obstruction for the average U.S. adult.

4.7.2 Scooters

For the 95% male mannequin, the seat position envelope for scooters had to be modified because the knees of the mannequin hit the fountain at the high/close position and because the mannequin could not touch the spout at the far positions. For the 5% female mannequin, the seat position envelope had to be modified because the mannequin could not reach the spout at the far positions.

The following table compares the front approach seat position envelope for scooters (shifted away from the wall 17 inches), with the seat position envelope for the drinking fountain obstruction for the average U.S. adult.

4.7.3 Recommendation: Drinking Fountain

In analyzing the above seat position envelopes for both power chairs and scooters, thirteen of the power chair seat positions fell within the envelope and four were outside of the envelope. Of these four, three were very close to the edge of the envelope boarder, thus it was assumed that 16 of the 17 seat position points for power chairs fall within the envelope. This is 94.1% of the power chairs. For scooters 36 of the 45 scooter seat positions fell within the envelope which is 80 percent of the scooters.

Based on the above no revisions to the standard or addition of explanatory notes are recommended.

4.8 Front Approach: Table with 36-Inch Clear Approach

The parameters for the analysis of the reach over an obstruction for the front approach are based on the reach over a counter or table with a 27 inch clearance below for knees and toes. A point 19 inches back from the edge of the table or counter is the touch point.

4.8.1 Power Chairs

The near portion of the chair profile meets the table at 27 inches, requiring the seat position point envelope to be moved 19 inches further back. We assumed that the power chair could be maneuvered into this 36-inch clear space in a forward approach position. For the 95% male mannequin, the seat envelope had to modified so that the upright mannequin could reach the touch point. The only point that does not require modification is the low/close seat position. For the 5% female mannequin, the seat envelope had to modified so that the mannequin could reach the touch point.

The following table compares the front approach seat position envelope for chairs with the seat position envelope for the table with 36-inch clear approach for the average U.S. adult.

An analysis of the above shows none of the power chair seat position points fall within the seat position envelope for this obstruction.

4.8.2 Scooters

A seat position envelope for the average U.S. adult could not be calculated for scooters. The 5th percentile female could not reach the touch point. Because the tillers on the scooters required the seat position envelope to be moved too far away from the wall.

4.8.3 Recommendation: Table with 36-Inch Clear Area

This table is a sectional view of ADAAG Figure 45, minimum clearances for seating and tables. Very few of the power chairs and none of the scooters could maneuver into the 36-inch clear space and execute a forward approach to the table because the power chairs and scooters hit the 27-inch high table and could not fit beneath it. Further, none of the power chair seat position points fell within the seat position envelope for this obstruction. Thus it is recommended that explanatory notes be added to ADAAG Figure 45 as follows:

Scooters can parallel approach the table by pulling into and backing out of the 36-inch wide space. The scooter seat can be rotated 90 degrees to simulate a forward approach. Most power chairs users will not be able to reach the touch point and many power chairs will not fit within this 36-inch space if the table is only 27 inches high because most power chairs will not fit under the table top.

This space should be reviewed in more detail using human testing to determine the appropriate height for the table because a 27-inch height will not accommodate very many of the power chairs.

4.9 Side Approach: Cabinet 34-Inch High, 24-Inch Deep

The parameters for the analysis of the reach over an obstruction for the side approach are based on an obstruction (e.g. counter) that is 24 inches from the wall and 34 inches from the floor. A point at 46 inches above the floor on the wall over the obstruction is the touch point.

4.9.1 Power Chairs

For the 95% male mannequin, the seat envelope had to modified at the low/close point for the upright mannequin to touch the wall at a point 34 inches from the floor. For the 5% female mannequin, the seat envelope had to be modified at both low/close and low/far points for the upright mannequin to reach the point on the wall.

The following table compares the side approach seat position envelope for power chairs with the seat position envelope for the 34-inch high, 24-inch deep cabinet for the average U.S. adult.

4.9.2 Scooters

For the 95% male mannequin, the seat envelope did not require any modifications. For the 5% female mannequin, the low seat position points had to be raised 12 inches for the mannequin to reach the touch point on the wall 46 inches above the floor.

The following table compares the side approach seat position envelope for scooters with the seat position envelope for the 34-inch high, 24-inch deep cabinet for the average U.S. adult.

4.9.3 Recommendation: 34-inch x 24-inch Cabinet

Many of the power chair and scooter seat positions fall within the seat position envelop for this obstruction indicating that most average adults would be able to reach over this obstruction. Even so, it is recommended that the following explanatory notes be added to ADAAG Figure 6(c), Maximum SideReach Over an Obstruction.

Some users of power chairs and scooters may not be able to touch the point on the wall behind the cabinet which is 46-inches above the floor.

4.10 Side Approach: Shelves

The parameters for the analysis of the reach over an obstruction for a side approach are based on an obstruction 12 inches away from the wall. Touch points are at 48 inches from the floor and at 9 inches from the floor at the intersection of wall and the shelves. The edge of the power chairs and scooters were positioned 4 inches away from the edge of the shelves, which is 10 inches from the center of the shelves.

4.10.1 Power Chairs

For the 95% male mannequin, the modified high seat position points had to be moved down and the lower seat position points were adjusted upwards to permit the mannequin to reach all the shelves. For the 5% female mannequin, the seat envelope had to be modified for the mannequin to touch the shelves. The high seat points had to be lowered and low seat points had to be raised.

The following table compares the side approach seat position envelope for power chairs with the seat position envelope for the shelves for the average U.S. adult.

4.10.2 Scooters

For the 95% male mannequin, both high seat points had to be move down to enable the mannequin figure to touch the bottom shelf. For the 5% female mannequin, the low seat position points had to be moved up and the high seat position points had to be moved down to allow the mannequin figure to touch both the higher and lower shelves.

The following table compares the side approach seat position envelope for scooters with the seat position envelope for the shelves for the average U.S. adult.

4.10.3 Recommendation: Shelves

These shelves are shown in ADAAG Figure 38(a), Storage Shelves. To make the bottom and top shelves reachable the power chairs and scooters were moved closer to the shelves. Therefore, it is recommended that the following explanatory note be added to ADAAG Figure 38(a).

Some users of power chairs and scooters may not be able to reach the top and bottom shelves if the edge of their mobility device is positioned 21-inches from the centerline of the shelves. If the users of power chairs and scooters can approach to within one or two inches of the face of the shelves then it is likely that they will be able to reach the top and the bottom shelves.

4.11 Side Approach: Clothes Hanger

The parameters for this analysis for side approach are based on a clothes hanger that is 21 inches from the edge of the power chair and scooter and 48 inches from the floor.

4.11.1 Power Chairs

For the 95% male mannequin, the mannequin in the upright position could reach the hanger. However, for the low/far seat position, the envelope had to be modified. For the 5% female mannequin, the seat envelope had to be modified for the mannequin to touch the hanger.

The following table compares the side approach seat position envelope for power chairs with the seat position envelope for the clothes hanger for the average U.S. adult.

4.11.2 Scooters

For the 95% male mannequin, the low/far seat position point had to be raised 4 inches. For the 5% female mannequin, both low seat position points had to be raised to permit the figure to reach the hanger.

The following table compares the side approach seat position envelope for scooters with the seat position envelope for the clothes hanger for the average U.S. adult.

Analysis of the power chairs and scooters seat position points that fall within the seat position envelopes for the clothes hanger shows 73.3% of the power chair seat position points fall within the power chair envelope and 87.1% of the scooter seat position points fall within the scooter envelope.

4.11.3 Recommendation: Clothes Hanger

The clothes hanger rod is shown in ADAAG Figure 38(b), Closets. Because a percentage of the power chair and scooter users could not reach the clothes hanger it is recommended that an explanatory note be added to this figure as follows:

Some power chair and scooter users may have to approach closer than 21 inches from the clothes hanger rod in order to touch the rod.

4.12 Clear Floor Spaces and Maneuvering Clearances

4.12.1 Power Chairs

A broad range of sizes of power chairs were included in our test population. The widest was 27 inches wide and 43 inches long and had a turning radius of 48 inches. The longest chair analyzed was 51.1 inches long, 25.4 inches wide, and had a turning radius of 42 inches.

The following table describes the results of the modeling of power chairs in the ADAAG clear space and maneuvering spaces by drawing number. The number refers to the figure number in ADAAG. "Yes" ratings indicate that the power chairs successfully navigated the listed space, and "No" ratings indicate that the power chair did not operate successfully in the space.

Clear Floor Spaces and Maneuvering Clearances - Power Chairs

 Longest Power Chair: 51.1 inches long and 25.4 inches wide

Widest Power Chair: 43 inches long and 27 inches wide

The longest and the widest power chairs were evaluated for each of the 35 ADAAG clear space and maneuvering space drawings to determine their fit and maneuverability within the clear spaces. The longest power chair in our test population was 51.1 inches. It fit within 10 of the spaces and was minimally outside of 5 of the spaces. Thus we assumed the longest chair would fit into and maneuver within 15 of the 35 spaces. The widest chair in the test population was 27 inches. It fit within 23 of the spaces and was minimally outside 2 of the spaces. Thus, we assumed that the widest chair could fit into and maneuver within 25 of the 35 spaces. ADAAG spaces that the widest and longest power chairs could not fit or maneuver in are listed in the following tables.

Widest Power Chair Could Not Fit

Longest Power Chair Could Not Fit

Based on the above results the following ADAAG spaces were reviewed in more detail.

• For Width only: 7b, 25c
• For Length only:4c, 4d, 4e, 25a, 23d 30a-1 46a, 35a
• For Width and Length:25b, 25c, 28, 30b

For this review we ranked the power chairs by size. The ranking was based on overall length as shown in the following table. The last column of the table shows the source of the dimensions.

Power Chairs - Ranking by Size

The power chairs in the above table were graphically tested in the ADAAG clear spaces and maneuvering spaces until a chair was identified that would fit within all of the spaces. The maximum dimensions of a power chair that could fit within all except one ADAAG space is 26.75 inches wide x 46.5 inches long. This length of 46.5 inches allows sufficient space for the toes of the person in the chair to fit within the spaces.

ADAAG Figure 28 illustrates clear floor space of 48 by 66 inches for a forward approach to water closet that does not provide side approach space. This design permits the 26.75-inch wide chair to approach the front of the toilet. The chair width could only be 20 inches to approach along the side of the toilet. Thus, we assumed a front transfer onto the toilet.

ADAAG Figure 30(b) illustrates alternate toilet stall designs with stall widths of 48 inches minimum and 36 inches. The 26.75-inch wide, 46.5-inch long power chair fits into the spaces on the following drawings but the stall door could not be closed.

The recessed area in ADAAG Figure 4(d) for a side approach is not large enough to permit the 26.75-inch wide by 46.5-inch long power chair to fit within it. The space is large enough to allow a 44-inch long by 26-inch wide power chair to fit into and maneuver within it.

Of the 33 power chair models for which we collected dimensional data, five of the models could not maneuver into all of the ADAAG spaces. These five models had overall lengths greater than 46.5 inches.

4.12.2 Scooters

Five three-wheeled scooters were graphically tested in the ADAAG clear floor spaces and maneuvering spaces (the largest, the smallest and three midsized). In addition, two four-wheeled scooters were tested (the largest and the smallest). The dimensions of the scooters and the designation given to each of the scooters are shown below.

Scooters Tested

The table below shows the results of the testing. "Yes" ratings indicate that the scooters successfully navigated the space and "No" ratings indicate that the scooters did not fit within the space.

Clear Spaces and Maneuvering Clearances - Scooters

Scooters were then ranked by overall length. The following table shows the ranking.

Scooters - Ranking by Size

The above scooters were graphically tested in the ADAAG clear floor spaces and maneuvering clearances until a scooter was identified that would fit within most of the spaces. The maximum dimensions of the scooter that could fit within most of the ADAAG spaces was 26 inches wide by 48 inches long. The toes of scooter users are within the scooter envelope, thus toe clearance is not a factor.

* Measurements from two comparative reviews.

In our analysis we made the assumption that the 26-inch wide by 48-inch long scooter would back into or out of the elevator cab, that is the scooter would not be turned around in the elevator cab. Two designs are shown in ADAAG Figure 22(a) and (b). A third design permitted in certain alterations allows a cab 48 by 48 inches with a centered opening 36 inches wide.

As with the power chairs, ADAAG Figure 28 (clear floor space of 48 by 66 inches for a forward approach to water closet) permits the 26-inch scooter to approach the front of the toilet. The scooter width would have to be 20-inches to enable a parallel approach, thus we assumed a front transfer.

The 48-inch long x 26-inch wide scooter could not maneuver into the recessed area for a side approach described in ADAAG Figure 4(d). Like the power chair, the maximum size of a scooter that can maneuver into this space is 44-inches long by 26-inches wide.

The 48-inch long x 26-inch wide scooter could not turn around in the 60-inch diameter circle specified in ADAAG (Figure 3). The information we were able to obtain from the literature, in particular a recent scooter study conducted by the American Association of Retired Persons indicates that very few scooters can turn around within a 60-inch diameter circle.

Of the 77 scooter models for which we had dimensional data, ten models were larger than this critical size, 48 inches long by 26 inches wide.

4.12.3 Recommendations: Clear Floor Spaces and Maneuvering Clearances

Since 28 of the 33 power chairs and 67 of the 77 scooters could fit into and maneuver within most of the ADAAG spaces, with the exception of those spaces noted, it is recommended that explanatory notes be added to the ADAAG figures as follows.

ADAAG Figure 28 - The following note should be added to the first drawing in ADAAG Figure 28:

The clear width along the side of the toilet is not wide enough for most power chairs and scooters to permit a transfer to the toilet by any means other than a front approach.

ADAAG Figure 30(b) - The following note should be added to ADAAG Figure 30(b):

The depth of the stall in this drawing is not sufficient for most power chairs and scooters to enter the stall and allow the stall door to be closed behind them.

ADAAG Figure 4(d) - The following note should be added to the second alcove drawing in ADAAG Figure 4(d):

The recessed area in this drawing is too short for most power chairs and scooters to maneuver into. If this configuration is used the maximum size for a power chair (including toe overhang) and for a scooter is 44-inches long by 26-inches wide.

ADAAG Figure 3(a) - Because this 60-inch diameter circle is not large enough for most of the scooters to turn around in, the following note should be added to ADAAG Figure 3(a):

The 60-inch diameter circle in this drawing is not adequate maneuvering space for most scooters. An 84-inch diameter circle will accommodate most scooters.

5. ADDITIONAL RECOMMENDATIONS

In addition to the specific recommendations listed in the previous section it is recommended that additional guidance be developed and presented in the appendix to ADAAG, referencing the following ADAAG Sections.

Section 2.1 Provisions for Adults

The dimensions and anthroprometrics for the 95th percentile U.S. adult male and the 5th percentile U.S. adult female should be averaged to determine the average U.S. adult dimensions and anthroprometrics.

Section 3.5 Definitions

Standard definitions should be developed and provided for (1) turning radius; (2) seat position point for wheelchairs, power chairs and scooters; (3) seat position point for the average U.S. adult; (4) seat position envelopes for front and side approach and reach over obstructions.

Section 4.1 Minimum Requirements

The design parameters for wheelchairs, power chairs and scooters should be defined to permit manufacturers to evaluate their own designs to ensure that they will comply with the prescribed ADAAG standards. Parameters that should be addressed are: (1) seat position envelopes for wheelchairs, power chairs and scooters; (2) the outside overall dimensions for power chairs; (3) outside overall dimensions for scooters and (4) turning radius.

Seat position envelopes should define the upper, lower, forward and rearward points that mobility aid seat positions can fall within to ensure that the average U.S. adult can touch the maximum/minimum reach ranges for front and side approaches and reach over the obstructions.

For the outside overall dimensions for power chairs, the maximum dimensions of a power chair should identified in ADAAG to provide guidance for the wheelchair manufacturers. The width of 26¾ inches and length of 46½ inches is the size of a power chair that will fit in and maneuver within most ADAAG spaces.

For the overall dimensions for scooters, the maximum dimensions of a scooter should be identified in ADAAG to provide guidance for the scooter manufacturers. The width of 26 inches and length of 48 inches are the dimensions that will fit in and maneuver within most ADAAG spaces.

A common definition and measurement system for turning radius should be developed and adopted. The turning radius should describe the diameter of the circle scribed by the outermost element of the device when it turns the tightest circle. A standard surface should be referenced, because surface texture directly impacts turning performance.

The number of and type of turning movements required to turn around in a tee corridor of 36 inches should be defined. A standard surface should be referenced for the tee corridor.

TECHNICAL ARTICLE

POWER MOBILITY AIDS STUDY LOOKS AT THE ADEQUACY OF CLEAR FLOOR
SPACE, MANEUVERING CLEARANCES, AND REACH RANGES

by H. Patricia Ohleger, Research Associate,KRW Incorporated

Because the Access Board has always intended the Americans with Disabilities Act Accessibility Guidelines (ADAAG) to be a "living document," the guidelines are reviewed periodically to allow for revisions based on new designs and technologies which provide for greater accessibility to people with disabilities. The technical specifications in the ADAAG assume that a person is using a manual wheelchair. Research on clear floor space, maneuvering clearances, and reach ranges has been based primarily on manual wheelchairs and their users.

Several factors have precipitated a significant increase in the number of persons using power mobility devices. These have included major advances in medical technology, longer life expectancy, and increased transportation, accommodation, and employment opportunities for individuals with disabilities. The dimensions and operating characteristics of power wheelchairs and scooters often restrict access to certain elements such as fixed tables, lavatories, and drinking fountains. They may also prevent an individual from approaching certain elements such as telephones and controls as closely as could be achieved using a manual wheelchair.

Because the specifications for motorized wheelchairs and for three- and four-wheeled scooters are substantially different than for manual wheelchairs, information was needed so that the Access Board could assess whether the current standards provided an acceptable level of access to the built environment for persons using these power mobility devices. The Access Board awarded a contract to KRW Incorporated of Alexandria, Virginia, to conduct a research project to study the relationship between the current requirements of ADAAG and the physical dimensions and operating parameters of power wheelchairs and scooters. The approach used by KRW in providing this assessment was to compile and review previous research, studies and related technical information; collect product information for power mobility aids; and develop an anthropometric model of adult body sizes of the average adult population in the United States. These three elements, the literature review, the product information, and the anthropometric model, were used to perform analyses that allowed KRW to assess whether the current standards provide an acceptable level of access for persons using these power mobility devices and to document in the final report recommendations derived from the analysis and simulations using the model.

The literature search focused on previous studies and technical information, on the clear floor space, maneuvering clearances, and reach ranges for power wheelchairs, three- and four-wheeled scooters and the users of these mobility aids. By being particularly sensitive to studies which described the tailoring of wheelchairs to the specific needs of individuals, insight was gained into the unique requirements of these individuals with respect to reach ranges. Parametric data concerning both front and side approach reach ranges was compiled. For side approach analysis, information was collected on seat height and placement and wheel chair width. For front approach analysis, information was collected on seat height and placement, and the approach profile of the mobility devices.

Dimensional data and operating performance information for the devices were obtained from relevant research, comparative studies published in industry and user periodicals, and manufacturer-supplied data. The data reported in the literature was compared with data provided by more than 20 manufacturers that responded to a mail survey. There was a large disparity in the data from the two sources and, as a result, it was decided that field measurements would have to be taken to ensure that the dimensional data to be modeled was accurate.

Information gathered was used to test current ADAAG requirements for clear floor space and maneuvering clearances, which are primarily a function of the overall dimensions of the devices. Reach range is a function of seat height and seat position, and the physical characteristics of the individual seated in the mobility aid. Field data was collected on design parameters that could be used in the testing of clear spaces and maneuvering clearances and in the modeling of reach ranges for mobility aids. These factors included wheelbase length and width, turning radius, front and rear extensions, total chair width and length, seat heights, seat positions, and forward approach profile measurements.

Analysis of the field data supported earlier observations of the research team:

• There is considerable variation in the number of models listed in the literature and those reported by the manufacturers.
• There is significant disparity in the dimensions and operating parameters provided by manufacturers, cited in the literature, and those taken in the field measurements, even for parameters that are easily measured.
• Dimensions cited in the literature and that provided by the manufacturers, when available for a specific model, seldom correlated exactly with field measurements.

The above observations were important because they pointed out a major issue with respect to research of the nature conducted by this project. There needs to be a standard guideline for measuring and reporting dimensions and operating parameters for mobility devices. If future research is to benefit from this effort and others like it, then each of those efforts must be able to build and expand upon the efforts that preceded it. In the absence of a standard for measuring and reporting specifications for power chairs and scooters, the proliferation of incomparable data will continue and the utility of data available to the public, wheelchair and scooter users, and the standard-setting agencies will continue to be questionable. The model used to evaluate the reach ranges from power chairs and scooters had two components: a human figure in a seated position, which could be adjusted to simulate different seat positions for mobility devices, and sectional views of specific ADAAG spaces that permitted analysis of reach ranges. Modeling of ADAAG spaces was accomplished using AutoCAD, Release 12, by Autodesk. Forty-four space drawings, taken from ADAAG, were drawn using the AutoCAD software. Nine of these drawings were needed to study reach ranges. The software allowed seated figures to be imported for selected power chair and scooter parameters to evaluate ADAAG reach ranges.

The ergonomic drawing and design software, Mannequin, Release 1.1, was used to model the human figure in a seated position. The Mannequin software models human figures in scaled settings and is the standard in the legal profession in modeling accident and crime scenes. The software permitted the human figure to be configured in various seated positions to model a person using a power chair or scooter. The figures were manipulated to sit, bend forward and to the side, and reach in an anthropometrically correct manner. The software incorporates 3-D drafting capabilities, including dimensioning, rotation, and scaling. The scaling feature was particularly important because the scale used in the CAD drawings was matched precisely to that of the human figure created by Mannequin.

In performing the analysis, the CAD-generated scaled drawings of the ADAAG spaces were used as the "operating envelope" against which product information and data collected in the literature review were assessed to determine if they "fit" within the ADAAG clear space and maneuvering clearance specifications. A combination of seat height, seat position, and anthropometric data, adjusted for the user population based on information found in the literature review was evaluated, to determine if the powered mobility aids and the average U.S. adult could reach the high and low points from the power mobility aids. Bad fits were identified for further study and evaluation for consideration in developing final report recommendations.

As a result of the study, recommendations were made for the Board to consider adding clarification in the Appendices of ADAAG pertaining to several scoping and technical specification sections of ADAAG. These included Scoping Sections 2.1, Provisions for Adults; 3.5, Definitions; and 4.1, Minimum Requirements. In the Technical Specification Section, it was recommended that clarifying notes be added to several ADAAG figures, including Figures 3(a), Wheelchair Turning Space - 60-inch Diameter Space; 4(d), Clear Floor Space in Alcoves; 5(b), Maximum Forward Reach over an Obstruction; 6(c), Maximum Side Reach over Obstruction; 28, Clear Floor Space at Water Closets; 30(b), Alternate Toilet Stalls; 38(a), Storage Shelves and (b), Closets; and 45, Minimum Clearances for Seating and Tables.

The findings and recommendations of this project will allow the Board to determine the impact of the ADAAG standards on the growing population of power wheelchair, three-wheeled and four-wheeled scooter users and whether current standards provide an acceptable level of access to the built environment for persons using such mobility devices.

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MANUFACTURERS

A-BEC Mobility Inc., 20460 Gramercy Place, Torrance, CA 90501

Action Technology, 34655 Mills Road, North Ridgeville, OH 44039

Advanced Technology Corp., P.O. Box 19412, Kansas City, MO 64141

AliMed, Inc., 297 High St., Dedham, MA 02026

Alpha Unlimited, 1610 Northgate Blvd., Sarasota, FL 34234

American Wheelchair Corp., 465 Cedar Lane, Teaneck, NJ 07666

Amigo Mobility International, Inc., 6693 Dixie Highway,Bridgeport, MI 48722-0402

BIOTECH LTD., P.O. Box 7036, Grays Lake, IL 60030

The Braun Corporation, 1014 S. Monticello, P.O. Box 310,Winamac, IN 46996

Bruno Independent Living Aids, 1780 Executive Dr., P.O. Box 84, Oconomowoc, WI 53066

Burke Mobility Products, P.O. Box 1064, Mission, KS 66222

Canadian Wheelchair MFG. LTD., 1360 Blundell Rd.,Mississauga, ON, Canada L4Y 1M5

Creative Controls, Inc., 4413 Fernlee, Royal Oak, MI 48073

Damaco, Inc., 5105 Maureen Lane, Moorpark, CA 93021

Dignified Products Corp., P.O. Box 337, Mantua, NJ 08051

Electric Mobility Corp., 1 Mobility Plaza, Sewell, NJ 08080

Everest & Jennings, Inc., 1100 Corporate Square Drive,St. Louis, MO 63132

Excel Mobility Products, Inc., 636 Constitution Avenue, N.E., Washington, DC 20002

Fortress Scientific, 6535 Millcreek Dr., Unit #42,Mississauga, ON, Canada L5N 2M2

Gaymar Industries, Inc., 10 Centre Dr., Orchard Park, NY 14127

Golden Technologies, 159 Penn Avenue, Exeter, PA 18643

Guardian Products, Inc., 4175 Guardian St., Simi Valley,CA 91331-4522

Hoveround Corp., 8135 25th Court East, Sarasota, FL 34234

Invacare Corp., 899 Cleveland Street, Elyria, OH 44036-2125

Jay Medical, Ltd., P.O. Box 18656, Boulder, CO 80308-8656

Jobst Institute, Inc., 5815 Carnegie Blvd., Charlotte, NC 28209

Joerns Healthcare, 5001 Joerns Drive, Stevens Point, WI 54481

Jubilee Scooters, Inc., 324 Lakeside Dr., Suite A, Foster City, CA 94404

Lark of America, P.O. Box 1647, W220 N597 Springdale Rd.

Waukesha, WI 53187-1647, Leisure-Lift, P.O. Box 6176,Kansas City, KS 66106

Love Lift, P.O. Box 2158, Holland, MI 49422-2158

Motech Design, Primulavej 6, 4340 Tollose, Denmark

Motion Designs, Inc., 2842 Business Park Ave., Fresno, CA 93727-1328

Motovator, 1733 Boarder Ave., Torrance, CA 90501

Newton Wheelchairs USA, 469 W. Ridge Rd., Rochester, NY 14615

Optiway Technology, 1250 Sheppard Avenue, West, Downsview,Ontario, Canada M3K 2A6

Ortho Kinetics Corp., P.O. Box 1647, Waukesha, WI 53187

Permobil, 30 Ray Ave., Dept. E

Burlington, MA 01803, Pin Dot Products, 2840 Maria Avenue,Northbrook, IL 60062

Prentke Romich Co., 1022 Heyl Rd., Wooster, OH 44691

Pride Health Care, Inc., 71 South Main Street, Pittston,PA 18640

Quest Technologies Corp., 766 Palomar Avenue, Sunnyvale,CA 94086-9716

Quickie Designs, Inc., 2842 Business Park Ave., Fresno, CA 93727-1328

Ranger All Season Corp., P.O. Box 8, George, IA 51237

Redman Wheelchairs, Inc., 945 East Ohio, Suite 4, Tucson,AZ 85714

RETEC, USA, 10 Centre Dr., Orchard Park, NY 14127

ROHO, Inc., P.O. Box 658, Belleville, IL 62221

Shoprider USA Inc., 7112 South 220th Street, Kent, WA 98032

Spenco Medical Corp., Box 2501, Waco, TX 76702-2501

Steven Motor Chair Co., 1020 N. Gunter, Siloam Springs, AR 72761

Sunrise Medical, 4175 Guardian Street, Simi Valley, CA 93063

Theradyne Corp., 21730 Hanover Ave., Lakeville, MN 55044

21st Century Scientific, 4915 Industrial Way, Coeur d'Alene, ID 83814

Voyager, Inc., 527 West Colfax, South Bend, IN 46601