1.2 Ensure that displays are within sight of people of all heights and people sitting in a wheelchair or buggy
Contents
A "display" encompasses anything from a single line LCD display to a CRT monitors. Being "within sight" means that the user's line of sight to the display is unobstructed at a distance and angle that enables the display to be read clearly by someone with 20:20 vision, within the environmental constraints such as ambient lighting (allowing for users with restricted vision is covered in other checkpoints). The display should be within sight from whatever position and orientation the user finds themselves in naturally when using the telephone. This will be different depending on the person's height and whether they are sitting in a wheelchair or motorised buggy.
Rationale
A display that is positioned for optimal viewing by users of average height may present difficulties for other non-average users. Users who are extremely short, extremely tall, or who sit in a wheelchair will be looking either up or down at the display and from further away. The increased distance may mean that fine text or information is difficult to read. The more acute angle may also affect readability by changing the aspect ratio. Or it may mean that other parts of the device get in the way.
Eye height ranges
Ensure that users of all heights can see displays. The standing eye height for the largest person (95th percentile) is approx. 1.8m. The standing eye height for the smallest person is approx. 1.35m. Wheelchair users often have eye heights as low as 1.15m.
A particular problem for people looking upwards at the display is the effect of reflected light. Some displays can be completely unreadable when a light source such as the sun is shining on them. Someone who is taller can often position their body between the light source and the display, making it easier to read.
Line of sight
Ensure that there is a clear line of sight to the display from a range of angles. Check for glare on the screen from a range of positions.
Directions and Techniques
Refer to anthropometrical data
Refer to appropriate physical design guidelines or building accessibility guidelines which give minimum and maximum heights. The United Nations have a useful set of anthropometrical datacovering ranges of height and reach when standing or sitting in a wheelchair.
Reduce glare
Anti-glare displays can help reduce the problem of reflected light. The physical design of the telephone installation can also help by blocking light from reaching the display. However, be aware that anything that obstructs light from reaching the display may also obstruct the user's view.
Increase size
Increasing the size of text or other displayed information can help to make it more readable at an angle.
Consider adjustable or extra displays
In extreme cases, you may consider using height adjustable or rotatable displays or dual-display systems.
How you could check for this:
Self-test early prototypes
Designers can run simple sight tests on a prototype, simulating short and tall people and wheelchair users by sitting in a chair, standing on a raised area or kneeling down. Whilst this will not be a replacement for proper testing with real users, it will give some insight into what it is like to be viewing the display from the user's perspective and will help reveal any obvious problems before further work is carried out. If standing on something, you should make sure it is sufficiently strong and stable and take care to avoid the possibility of injuries caused by falling off it. Difficult lighting conditions are easily simulated by either using the prototype outside in sunlight or positioning artificial lights appropriately.
Include user data in the design
If you are designing using a CAD package, you may be able to simulate different viewing points before creating a prototype.
Test with real users
During development, you should test the prototype in a realistic situation with real people, particularly people who routinely use wheelchairs or motorised buggies.
About user testing