I want to build a telescope which is wheelchair accessable.
So I need the following ergonomic information:  What is the
median height (and standard deviation )from the floor, to 
eye-level of a representative sample of the US population.  
(Assume the individual can sit up straight.)

Second, what is the typical height of the side rails on
wheel chairs, and a typical width (or door width requirement?)

Hi,

You've come up with a great idea! I personally know someone who would
love to get more information about your product when it's finished!

I was able to find several sources quoting the average height of a
wheelchair-bound person. While I was unable to find any one "official"
source, most of the values specified by these various sources more or
less coincide with each other, so you should be able to get a very
good idea of the average.

- The best place to start would be what the United States Govornment
thinks. In a consent order from 1995 suing a company under the
Americans with Disabilities Act, the United States specified:

"The average anthropometric dimensions employed shall be: (1) average
eye height for a person sitting in a wheelchair is 47.45"; (2)
horizontal distance from the eye of an average person sitting in a
wheelchair to the edge of the tier on which the wheelchair rests is
30"; (3) average head height of a standing spectator is 67.65"; (4)
average eye height of a standing spectator is 63.45"; and (5) average
shoulder height of a standing spectator is 55.65"."

Exhibit B (bottom of page):
http://www.usdoj.gov/crt/ada/ellerbe.htm

- A 1979 Study by Steinfield, Shroeder & Bishop is quoted in this
Department of Transportation document relating to different types of
pedestrians. It specifies:

"Based on the results in Table 2-2, the HUD study recommended that the
eye level for wheelchair users be considered as a range from 0.890 to
1.320 m (35 to 52 in)."
http://www.fhwa.dot.gov/environment/bikeped/07-chap2.pdf (Adobe PDF
Reader required)
This page also includes a chart outlining more specifics from this
study.

- The San Fransisco Mayor's Office on Disability provides a guideline
for eye-level viewing height of telescopes:

"2. If provided, telescopes or periscopes shall be configured to
permit viewing from eye level heights of 32" to 51". This may be
accomplished by providing multiple units fixed at varying heights or
by providing one or more adjustable units which accommodate variable
viewing heights. "
http://www.ci.sf.ca.us/sfmod/html/atbcb-p20.htm

- Durham County Council in the UK lists the average eye-level height
of a wheelchair as "between 1175 - 1265mm", which would equal about
46" (3.8ft) to 49" (4.1ft):
http://www.durham.gov.uk/DurhamCC/usp.nsf/web/pages+with+sections/Sust+comms+-+Improve+Access+to+Public+Buildings+and+Open+Spaces

- Page 5 of the following Cornell University document provides some
interesting statistics, including the following sentence:

"Lower eye-level - eye-level is 15 to 16 inches below that of most
standing people"
http://ergo.human.cornell.edu/studentdownloads/DEA325pdfs/anthropometry.pdf
(Adobe Acrobat Required)

- In general, I recommend reading The ADA Accessibility Guidelines for
Buildings and Facilities (ADAAG), which provides several guidelines
which are appropriate to your question. It includes, among other
things, the door width requirement you inquired about:

"4.13.5 Clear Width. Doorways shall have a minimum clear opening of 32
in (815 mm) with the door open 90 degrees, measured between the face
of the door and the opposite stop (see Fig. 24(a), (b), (c), and (d)).
Openings more than 24 in (610 mm) in depth shall comply with 4.2.1 and
4.3.3 (see Fig. 24(e))."
http://www.access-board.gov/adaag/html/adaag.htm

Regarding the wheelchair dimensions you asked about, there are several
resources that provide this information. The two most descriptive I
found were the following:

- Accessibility Design Manual at the United Nations:
http://www.un.org/esa/socdev/enable/designm/AD5-02.htm

- The University of Memphis specifies:

"It is 27 in. from the floor to the user's lap and 30 in. form the
floor to the armrests."
http://216.239.37.100/search?q=cache:a66O5NDS9xoC:www.hmse.memphis.edu/faculty/walls/Accessible%2520%26%2520Usable%2520Leisure
[This is a Google Cache version of the document]

I hope the above links were what you hoped for. If you require any
further clarification, don't hesitate to ask!

Search terms I used:
wheelchair "average height"
wheelchair "eye level" height
anthropometric wheelchair "eye level"
anthropometric data "seated adult"
average wheelchair dimensions

Have a great day, and good luck with your design!

Axe

Excellent prompt job!  You got me the data I needed.

I'll be back to use this service again!

Wayne

Your best bet is likely to follow the Americans With Disabilities Act
(ADA) guidelines:
	
ADA Accessibility Guidelines for Buildings and Facilities (ADAAG)
http://www.access-board.gov/adaag/html/adaag.htm

From these guidelines, the minimum width of a route is 36”, and of
doorways, 32”. Section 4.27, Controls and Operating Mechanisms, is
probably of particular interest. It specifies height and references
4.2.5 and 4.2.6 for reach:

“the maximum high forward reach	allowed shall be 48in. The minimum low
forward reach is 15in.”

Starting from the ADA guidelines you ought to be able to design a nice
accessible telescope setup

Question 1:
This seems to be a hard question to answer.  Clearly, the truth is out
there, but it's not clear who if anybody knows it.  One rule of thumb
is to use a figure on the Cornell University Ergonomics Web (see
below), that wheelchair users will have average eye heights of 15 to
16 inches below standing level.  Another average eye height figure is
47.45" (given in a US District Court judgment).  I could not find data
on variation or standard deviation of eye height specifically, but the
U.S. Transportation and Architectural Barriers Board seems to have set
the outside limits of head height for wheelchair users at 2.9-8.3
(presumably feet).  This range is clearly quite large, but as a
wheelchair user who has met many others in my lifetime, I think it may
indeed be reasonable.  You may want to consider whether you are
designing for all people in wheelchairs, or for some subset of them,
e.g. those in standard-size manual wheelchairs.


Cornell University Ergonomics Web DEA325/651 CLASS NOTES

http://ergo.human.cornell.edu/DEA325notes/anthrodesign.html

"Lower eye-level - eye-level is 15 to 16 inches below that of most
standing people and the seated posture also influences
reach, controls, and access"


A case in the US District Court established this standard for eye
height of wheelchair users as part of ruling about accessible sports
facilities.  They don't say where they got it.

http://www.usdoj.gov/crt/ada/ellerbe.htm
The average anthropometric dimensions employed shall be: (1) average
eye height for a person sitting in a wheelchair is
47.45"


ANTHROPOMETRY FOR PERSONS WITH DISABILITIES: NEEDS FOR THE
TWENTY-FIRST CENTURY
Analysis and Recommendations prepared for U.S. Architectural and
Transportation Barriers Compliance Board

http://216.239.33.100/search?q=cache:CIIoauzQE64C:www.access-board.gov/research%26training/Anthropometry/anthropometry.txt+anthropometric+wheelchair+eye+height&hl=en

Contains a discussion of the difficulty of establishing dimensions for
the disabled population and proposals for research.  Cautions against
the use of figures for one disabled population (e.g. paraplegics) when
designing for all people with disabilities.  Calculates a range of
2.9-8.3 (presumably feet?) as the design assumptions for the sitting
height of people in wheelchairs, which they say is taken from an
(unstated) mean and standard deviations in a representative sample.


As I mentioned above, there seems to be something of a consensus that
there needs to be more research on anthropometric standards for people
with disabilities.
Several people lamenting the lack of data:

ergo.human.cornell.edu/DEA325notes/anthrodesign.html - 12k - Cached -
Similar pages

www.vard.org/jour/99/36/1/coope361.htm

http://isb.ri.ccf.org/biomch-l/archives/biomch-l-1997-01/00180.html


If the above is not enough, these people might be able to help you,
even though they haven't put their information on the web.

University of Buffalo Anthropometric Research Laboratory

http://www.eng.buffalo.edu/Departments/ie/Facilities/Laboratories.htm

                  "This lab is dedicated to the study of body size and
function for the improved design of living, public and
                  occupational settings. At present, the laboratory is
being used for a five year study funded by the National
                  Institute on Disability and Rehabilitation Research
through the Rehabilitation Engineering Research Center for
                  Universal Design at Buffalo. The Center is Directed
by Dr. Steinfeld, Professor, Department of Architecture.
                  Dr. Paquet is working as Co-principal investigator
on the Center's largest research project which involves the
                  develoment of a prototype anthropometric database of
wheelchair users to serve as a model for
                  anthropometric research in universal design. The
study includes the development and evaluation of
                  anthropometric methods that record 3-dimensional
coordinates of body dimensions, collection of dynamic
                  (functional), as well as static anthropometric data,
and the development of the database to be used by
                  designers and to support computerized human models
of wheelchair users."



Question 2:
This one is much more straightforward.  The door/path width should be
36".  The handrim height of a standard (24") wheel is 22.5".

From the ADA Accessibility Guidelines for Buildings and Facilities

http://www.access-board.gov/adaag/html/adaag.htm

"4.3.3 Width. The minimum clear width of an accessible route shall be
36 in (915 mm)" (note that the rules are different around corners and
at doorways to give maneuvering/turning room; see the ADA rules for
specifics and diagrams)

The standard width for an accessible door is 36", although they are
allowed to be as narrow as 32" in old buildings.

Also, in case it's of interest:  when sitting "clear floor space shall
not overlap knee space by more than
19 in (485 mm)" and "[t]he tops of accessible tables and counters
shall be from 28 in to 34 in
(710 mm to 865 mm) above the finish floor or ground."

A standard chair width is 28", but the ADA allows for wheelchairs of
up to 30".  I know that in fact some are larger than that.  There are
quite a few narrower ones, too.


I got the handrim height by measuring my wheel, which I know is
standard for a manual chair.  Note, though that a) not everybody uses
a standard-height wheel, and b) only manual (as opposed to power)
chair users have handrims on their wheels.


Good luck with the project!


Search terms used:

anthropometric wheelchair 
wheelchair eye height

Hi,
Good luck with your new product.  Keep in mind that wheelchair users
have many other needs besides height - such as differing strength and
range of motion in the upper arms.  Such a telescope, to be really
useful to many or most wheelchair users, would have to be flexible to
move in other ways, also.
Thanks for a great idea!

Remember whenever you use anthropometric stats on anything, DO NOT USE
THE MEAN.  The goal is to design so that the smallest can reacy and
the largest can fit so use 5th and 95th percentile data for the best
results.

ergojoan