2 Learning about mobility of vision impaired people

2.0 Purpose of this section

This section provides an introduction to vision impairment and the mobility aids and techniques used by vision impaired people to navigate their way around in the course of their everyday lives. The aim is to inform anyone who is involved in installing and operating wayfinding systems in built-environments as well as creating navigation services and products for vision impaired people.

2.1 Some facts about vision impairment

According to the World Health Organisation (WHO) [9, 10], there are an estimated 285 million vision impaired people worldwide. The vast majority live in less developed countries, in low income settings and are aged over 50. The most common causes of vision impairment globally in 2010 were:

1. refractive errors – error in how the eye focuses light – 42%
2. cataracts – a clouding of the lens in the eye – 33%
3. glaucoma – a group of eye diseases which result in damage to the optic nerve and vision loss – 2%

The World Health Organisation (WHO) [9, 10] classifies the levels of vision impairment as :

• Normal (full) vision – no visual impairment
• Moderate vision impairment
• Severe vision impairment
• Blindness

About 15% of people who are registered as having vision loss cannot see anything at all [10]. The remaining 85-90% may have residual vision or other types of low vision and may have difficulties with colour, light, form or movement perception.

2.2 Primary mobility aids

The most commonly used primary mobility aids in many countries are a (long) white cane and a guide dog (“seeing eye dog”). Vision impaired people might be using one or both of them depending on the environments they are travelling through. Generally, guide dog users have long cane skills, as good orientation and mobility skills are required to ensure that the guide dog is guiding the person who is vision impaired in the correct manner and along the routes that the user specifies.

In those countries and cultures that use them, the primary role of the guide dog is to walk in a straight line avoiding obstacles in the person’s path of travel. It is the job of the guide dog user, however, to give the dog commands and direct the dog to find certain features of the environment and get to a destination. Guide dog users often ask their guide dog to target a specific landmark such as a door, steps, escalator etc., a task that is called “targeting”. Guide dogs are able to memorise a route; however the user always needs to be aware of the environment they are travelling through and cannot rely totally on the guide dog to get to a destination. The guide dog needs support and encouragement from the user to ensure that the person is safe and gets to a destination.

There are three types of cane that a person who is vision impaired may use:

• Long cane: Used by people with little or no vision.
  • A long cane allows the user to detect obstacles and hazards, drop-offs/kerbs, ground level changes and stairs in the path of travel.
  • A long cane provides information from the environment that assists orientation. For example, the cane user can detect changes in surface textures between grass and concrete to follow a footpath.
  • Many cane users experience an increase in confidence because they hesitate less about the safety of the next step.
  • A long cane improves the user’s posture, because they don’t need to feel the ground with their feet while travelling or walk with the head down to check the surface directly at their feet.
• Identification/symbol cane: This cane is a tool that allows the general public to identify a person as having a vision impairment. This cane is not designed to make contact with the ground surface, but may be used to check the height of a step or drop-off/kerb.
• Support cane: The white support cane allows a person who requires balance and stability support to be identifiable as having a vision impairment.

Any navigation service should not replace the primary mobility aids, but rather it should be treated as an orientation tool used along with other skills to augment the user experience and reassure its users.

2.3 Orientation and Mobility (O&M) training

In many countries, some vision impaired people receive Orientation & Mobility (O&M) training. This is usually one-to-one training with a Mobility Specialist and the vision impaired person learns techniques and skills that will help them to travel safely and independently in their environment.

In the context of Orientation & Mobility training, orientation refers to the knowledge of the individual of where they are located in an environment and how they will get to a destination confidently and safely [6].

Some of the skills that may be covered in this type of training include using residual vision, sensory awareness, understanding how objects relate to each other in one’s environment, how to search for places and objects, personal safety and cane usage.

The techniques for long cane training are outlined below:

• The cane is used with the index finger held alongside the cane so that the cane acts as an extension of the finger to provide a tactile experience of the ground one pace ahead of the user. Each user will be measured and fitted with a cane to match their height, length of stride and walking speed.
• Touching or Constant Contact: The cane user moves the cane in an arc from left to right, slightly wider than their shoulder width to ensure that they preview the environment prior to moving forward in order to detect features such as barriers, upward or downward slopes and obstacles. Touching or Constant Contact technique allows the user to arc the cane from left to right while keeping constant contact with the ground surface.
• Two-point touch: This is where the cane user taps the cane to the left and right instead of keeping constant contact with the ground. This allows the person to get audio feedback about the environment from the cane taps.
• Shorelining is following a wall, kerb, hedge or other contrasting surface to the one a person is walking on in order to maintain a specific orientation while travelling through environments to arrive at a decision-making point. Shorelining allows a person to arc the cane either by constant contact or two-point touch technique to cross an open space or easily travel towards a known point in a crowded environment. Shorelines are an important element of how a vision impaired person navigates. There are two shorelines:
  • Inner shoreline, in the junction of a ground surface and a wall
  • Outer shoreline, in the junction of pavement and kerbline
• Trailing is different to shorelining in that the technique allows a person to trail a contrasting surface such as a wall with their hand. The degree to which people use shorelining or trailing depends on the individual, their orientation and mobility skills and the environment they are in at any one time. Generally shorelining is the preferred technique in public places.

Importantly, those who are experienced travellers may not use shorelining or trailing. Each traveller differs in their approach to different techniques, so designers should not refer to shorelines or trailing as the only techniques to use in their environments. Rather they should design a system that refers to different features of the environment.

2.4 Landmarks and clues

Primary landmarks are defined as objects always found in the environment that are difficult to miss at a particular location such as kerbs, a change in walking surface etc.

Clues are more transient and may include sounds, smells, change of temperature etc. Clues may include the noise of machinery but this may only be present in the working day, smells of the baker’s shop or dry cleaners, the change of temperature as you enter the open door to a building providing the air conditioning/heating is working.

Landmarks and clues play an important role in wayfinding and navigation, as they reassure the individual that they are walking in the right direction as well as helping to place themselves in the space [1].

Sighted people can easily identify features in the environment that they use as for this purpose. Vision impaired people also make use of landmarks and clues as they move, although they may be different to those used by sighted people. Orientation & Mobility experts define clues and landmark as, “any familiar object, sound, smell, temperature, tactile or visual clue that is easily recognised, is constant and has a discrete permanent location in the environment that is known to the traveller.” A clue can include the sounds, smells, temperature, tactile clues etc., whereas a landmark is a specific and permanent feature, which is familiar to the user.

Vision impaired people tend to use different clues and landmarks than sighted people, sometimes more detailed ones [2, 7]. Most seem to be closest to the individual [6] in other words in the areas that can be touched by the long cane or felt through the soles of the feet.

Non-visual cues such as wind direction, smell of the bakery, soap shop, heat from the sun are more inconsistent and so considered less reliable. In order to increase the reliability of the clues used, vision impaired people often combine the use of different senses. For example they may use a tactile landmark followed by an auditory clue in order to confirm that they are approaching a landmark [2].

None of the above should be seen as supporting the myth that blindness sharpens other senses but rather, that it makes vision impaired people pay more attention to their available senses in order to cognitively process the information from the environment.

2.5 The safest, not the fastest or shortest route

For most digital navigation services the main criteria for calculating the shortest route are distance and time taken. Some navigation services have additional criteria such as quieter routes, less stressful routes and those with fewer changes.

During Wayfindr trials and in other work by other researchers [3, 5, 8] vision impaired people reported that they are willing to walk further provided that the longer route is considered safer and easier to manage. For example, instead of crossing a hotel lobby where there are a lot of people waiting with luggage they might prefer to walk all the way round the lobby rather than face obstacles and the potential danger of collision and/or loss of orientation. This makes their journey less stressful and enhances confidence. Thus the shortest or quickest route may not be appropriate for some vision impaired people.

Routes should be planned using a combination of what is considered a safer route and less challenging for the individual and with the advice of Orientation and Mobility specialists. A number of different routes should be considered as some travellers will prefer certain routes depending on their travel skills, the situation and where they need to get to at a given time. Guide dog users however will utilise the dog’s ability to avoid obstacles, pedestrians and other hazards along with its ability to target the interim or final destination, which may result in them taking the shortest, most direct route.

Some partially sighted people, for example, confident independent travellers, may still prefer the shortest or quickest route to their destination. Therefore, it should not be assumed that a difficult route for one vision impaired person might be the same for another.

NB. This functionality, offering alternative and personalised routes, is not currently demonstrated in the Wayfindr Demo iOS app v0.4.

2.6 User preference for discreet technology

Holding a device

During Wayfindr trials, vision impaired people reported that they would feel vulnerable holding a smartphone in their hand when navigating public spaces, e.g. because of the risk of having it stolen. They also pointed out that with one hand usually holding their primary mobility aid they need the other hand to be free to hold handrails or their ticket. For these reasons most people would be prefer to keep the smartphone in their pocket.

Even with the device in the pocket it should be able to communicate with Bluetooth beacons and trigger instructions at the appropriate time. Based on the Bluetooth antenna orientation and the signal reflection, the instructions might be triggered earlier but this should not cause a problem for users if the beacons have been installed and calibrated following the best practices as seen in Section 5.1 “Bluetooth Low Energy beacons.”

Listening through headphones

In busy and noisy environments, hearing audio instructions from a smartphone speaker, particularly when in a pocket, will be a challenge. During Wayfindr trials and in the work of other researchers [4], vision impaired users reported that they do not like using headphones whilst moving around as they block out auditory clues and warnings in the environment. Bone conducting headphones might offer a good solution.

Additionally, vision impaired people have reported that ideally they would like to use wireless headphones to avoid wires becoming tangled. Bluetooth headphones might be a solution. However due to the limitations of Bluetooth technology, there may be a time delay in the delivery of the audio instruction to the Bluetooth headphones that might be a problem for the user.

2.7 References

1. Allen, G. L. (1999). Spatial abilities, cognitive maps, and wayfinding. Wayfinding behavior: Cognitive mapping and other spatial processes, 46-80.
2. Fryer, L., Freeman, J., & Pring, L. (2013). What verbal orientation information do blind and partially sighted people need to find their way around? A study of everyday navigation strategies in people with impaired vision. British Journal of Visual Impairment, 31(2), 123-138.
3. Gaunet, F., & Briffault, X. (2005). Exploring the functional specifications of a localized wayfinding verbal aid for blind pedestrians: Simple and structured urban areas. Human-Computer Interaction, 20(3), 267-314. (last accessed: 24 February 2016)
4. Golledge, R., Klatzky, R., Loomis, J., & Marston, J. (2004). Stated preferences for components of a personal guidance system for nonvisual navigation. Journal of Visual Impairment & Blindness (JVIB), 98(03). (last accessed: 24 February 2016)
5. Helal, A. S., Moore, S. E., & Ramachandran, B. (2001). Drishti: An integrated navigation system for visually impaired and disabled. In Wearable Computers, 2001. Proceedings. Fifth International Symposium on (pp. 149-156). IEEE. (last accessed: 24 February 2016)
6. Long, R. G. & Giudice, N. A. (2010). Establishing and maintaining orientation for orientation and mobility. In B. B. Blasch, W. R. Wiener & R. W. Welch (Eds.), Foundations of orientation and mobility (3rd ed. Vol.1: History and Theory, pp. 45-62). New York: American Foundation for the Blind. (last accessed: 24 February 2016)
7. Passini, R., & Proulx, G. (1988). Wayfinding without vision an experiment with congenitally totally blind people. Environment and Behavior, 20(2), 227-252. (last accessed: 24 February 2016)
8. Swobodzinski, M & Raubal, M. (2009). An indoor routing algorithm for the blind: development and comparison to a routing algorithm for the sighted. International Journal of Geographical Information Science, 23(10), 1315-1343. (last accessed: 24 February 2016)
9. World Health Organisation, Fact Sheet No 213, Blindness: Vision 2020 – The Global Initiative for the Elimination of Avoidable Blindness. (last accessed: 24 February 2016)
10. World Health Organisation, Fact Sheet No 282, Visual impairment and blindness. (last accessed, 24 February 2016)