In order to facilitate use by product design teams, this section is organized functionally rather than by disability area. Functional categories are as follows:
Input/Controls includes keyboards and all other means of communicating to the product
Manipulations includes all actions that must be directly performed by a person in concert with the product or for routine maintenance; e.g., inserting disk, loading tape, changing ink cartridge
Documentation primarily operating instructions
Safety includes alarms and protection from harm
Each guideline is phrased as an objective, followed by a statement of the problem(s) faced by people with disabilities. The problem statement is accompanied by more specific examples. Next, "design options and ideas" are presented to provide some suggestions as to how the objective could be achieved. Readers are encouraged to think of other ideas. Finally, additional data and specific information, along with illustrations, are presented at the end of each guideline.
The guidelines are stated as generically as possible. Therefore, all, some or none of the design options and ideas presented may apply in the case of any specific product. The recommended approach is to implement those options which together go the longest way toward achieving the objective of the guideline for your product. It is understood that this is not an ideal world, so it may currently be too expensive to implement all those ideas which would best achieve the objective. It is also anticipated that there will be other ways of meeting accessibility objectives than those discussed here, and such discoveries are encouraged. We would like to hear of them so that they can be included in future releases of these Guidelines.
In trying to make products more accessible, the question of numbers quickly arises. How large should lettering be? What size button is large enough? How much pressure is too much, or not enough? In trying to make designs more accessible there are two tough principles that one has to come to grips with early.
At first this is hard to accept. Everyone wants a number to design to. Occasionally minimal numbers for minimal required accessibility are set, but ...
This latter point is the most important. A key problem in picking or setting a number is deciding who to leave out. The reason for discussing accessible design in the first place is that the standard design process currently only targets "most" of the people, and then stops. Some target number is established that is "good enough" to cover 80%, 90% or 95% of the people, and then developers end up designing to that number and stopping - even if they could just have easily gone a bit further. And it is that last phrase that is important. Since no product can be made completely accessible, a designer can't ever win completely. Tough to accept or deal with, but a fact of life. The secret, then, is to go as far as one can in making the design accessible. Setting a number as "good enough" for "most people with disabilities" and then designing to it just repeats the mistake that was made in the standard design process.
For example, to specify exactly how large lettering should be in order to be visible, you must first ask "visible to whom?" For any number you cite, there will be people who could see it if it were just a little bigger and others who would be unable to read it if you made it any smaller. There would also be some who could not see it no matter how large you made it. Thus, there is no number that will allow all people to read it. You always end up leaving some people off. The question then isn't "How large must lettering be to be accessible?" The proper question is "How large can this lettering be and still work for this product?" The decision to make it as large as practical will make the product accessible to a greater number of people. However, the decision as to the exact amount of enlargement that can be effectively used on the lettering for any given product is a decision that must be made as a part of the design process for that specific product.
This is not to say that numbers are not useful. They are essential to any design process. The numbers needed, however, are not "target" numbers or "this is now accessible" numbers, but rather numbers that a designer can use as milestones to see how changes in a design will affect users. Whenever data of this type exist or are identified they will be either included or cited in these Guidelines. An example of this is Figure O-7-a on the sensitivity of people with photosensitive epilepsy to different flicker frequencies. The chart does not give a magic frequency that would be safe (wouldn't trigger a seizure in anyone) under all conditions. It does, however, clearly indicate that avoiding 20 hz flicker by as much as practical will clearly be to the benefit of those with photosensitive epilepsy.
Occasionally, recommended "minimum" or "maximum" values do exist. Sometimes they are created as part of regulations or standards which set a baseline that everyone must comply with for some product or market. In other cases, "rule of thumb" values exist which are known or believed to cover the majority of people or situations. As the new accessibility standards for ADA compliance are finalized, for example, those that might apply to consumer products will be included in these Guidelines for reference. In all cases, however, these values should be used as milestones and not as absolute or "good enough" design targets. If it is possible to go beyond the value and create a more accessible design, then that should be considered.
The role of these Guidelines, then, is more to raise the awareness and understanding of designers and to help them ask the right questions than to provide specific answers or numbers. Notwithstanding, wherever specific design ideas or "recommendable" values do exist, they are provided. When they do not, general recommendations or design ideas are provided to help designers identify areas where attention can increase accessibility. In addition, data are provided when available to help designers measure the impact of various design decisions or tradeoffs.
In all cases, however, the exact values to use for a given product design will have to be determined by balancing the various design factors and constraints for that particular product. They cannot be dictated a priori without picking a number which will be too restrictive for some designs and unnecessarily loose for others.
Often, initial attempts at accessible design are done piecemeal. Accessible features are added where they are obvious rather than as a result of looking at the product's overall accessibility. The result can be a design which has accessible parts, but is not as a whole accessible or usable. Access to half a product when the rest is inaccessible is of little practical use.
In some cases, inspired by a desire to address the needs of people with different disabilities, it is even possible to design some parts of a device (such as the controls) to be more accessible to one population and design another part of the product with another disability in mind. Unless the whole product is accessible to at least one of these populations no-one is served.
In most cases it is possible with careful design to create products which are simultaneously accessible to people with different impairments. However, where this is not possible, care should be taken to be sure that the entire product is accessible to those disability populations that you are able to address. Giving half a product to one disability group and the other half of the product to another is not helpful to or desired by any of the disability groups.
Sometimes a solution to a problem for one type of disability may cause a new problem for a person with another type of disability. For example, those with visual impairments may be helped by replacing a visual readout with auditory output, but this would in turn cause a problem for those with hearing impairments. As such situations arise, the Guidelines will attempt to highlight them and suggest ways to avoid or minimize any potential conflicts.
At the end of most sections, a summary of the recommendations, along with examples of balanced solutions, is presented. These are not the only, and perhaps not the best, solutions. They do, however, show how multiple recommendations can be addressed even when they seem to be contradictory. They also illustrate that it is usually impossible to follow all of the recommendations simultaneously.
NOTE: The ADA guidelines are currently under development and the ANSI standards for accessibility are currently under revision. When these activities are completed, specifications for minimum levels of accessibility for some types of structures and products will be spelled out. As these minimum values are defined they will be added to these guidelines in the sections to which they apply. To avoid confusion existing and proposed standards are not included in this draft.