Electronic Travel Aids - why bother?

One of the major goals for vision impaired people is independent mobility. Two professions exist to cater for this: Orientation and Mobility Instructors who predominantly work with Long Canes, and Guide Dog Instructors who work with dogs. Many newly blind people ask about Electronic Travel Aids. My advice has always been, to not start by considering electronic travel aids, the Long Cane and the Guide Dog are the established primary mobility aids and both are very good.

Let us assume the vision impaired person chooses to have either Long Cane training or Guide Dog training. ( In fact, the choice is mainly one of lifestyle and the availability of one or other type of training. It has little to do with the vision condition. Many users of both type of primary mobility aid have some residual sight.) Now the question at the head of the page becomes relevant, "Electronic Travel Aids - why bother?" Rephrasing the question less crudely one should ask,

Early Electronic Travel Aids attempted to present too much information. They were vision substitution systems which were designed to provide users with a 'picture of the world' through their unimpaired senses. The hope was that these devices would provide an alternative to vision which would remove the need for the vision impaired person to be reliant upon such things as canes and dogs. This hope lives on in numerous engineering departments all over the world! Real progress was made, however, when psychologist Alfred Leonard, the founder of the BMRU, performed a very simple but revealing experiment. Leonard found that if he were to walk just behind a blind person and quietly whisper information, he could turn a mediocre long cane performance into a smooth, graceful and safe performance. He further found that very little information was sufficient to achieve this huge increment in performance. He concluded that what was required is an electronic aid which provides very small amounts of relevant information and that the information should be delivered to the vision impaired pedestrian in such a way that it does not interfere with the information already being gathered and used.

On the basis of this and other work relating to the evaluation of existing electronic travel aids Leonard concluded that, rather than attempt to develop vision substitution systems which would replace the primary mobility aids we should develop devices designed to supplement the primary mobility aids. Furthermore, he suggested that the value of such aids should be judged, not in terms of the richness of the information provided to the user but rather in terms of the benefit given to the mobility performance.

So what are the shortcomings of the Long Cane and the Guide Dog which require them to be supplemented? There are three basic problems: orientation with respect to the general environment, orientation with respect to the local environment, and the detection of hazards not detected by the use of the primary mobility aid.

The first of these problems, general orientation, is the subject of much current research. The advent of global positioning satellites and cellular telephone networks offer the possibility of delivering to the vision impaired pedestrian information which will pinpoint his position with great accuracy. The most important need is for work to be done on user friendly displays, cost and weight saving. My own work has address the second and third problems: local orientation and the detection of otherwise undetected hazards.

Research has shown that Long Cane users are unable to maintain a straight travel path in the absence of some external input. Those fortunate to have good hearing will manage straight line travel along the side of a road carrying traffic and in some cases when walking along a wall listening to the echo of their cane and foot steps. Others with less good hearing have to rely on cane contact with the ‘shore’ line or side curb e.g. the cane technique known by Orientation and Mobility Instructors as ‘touch and drag’. Guide Dog users admit to being almost completely ignorant of the features which boarder their routes. The dog is terrific at whisking them through the environment without contact or knowledge of their surroundings. In both examples it is not difficult to imagine what additional information would be relevant. Since independent travel is goal directed, one must not only avoid things, one must find things. If anyone has any doubt about the above analysis I would suggest that they send a Long Cane user or a Guide Dogs user to post a letter and watch what happens.

The Long Cane will not detect hazards above waist height unless, of course, the hazards continue down to the ground. Long Cane users must rely on their natural hearing, either echoes or sound shadows, to perform these detection feats. Indeed an important part to the Long Cane training is the training of auditory skills. Guide Dogs, in the main, are quite good at detecting and avoiding head high objects. In spite of the fact that these objects are well clear of the dog. Once again, it is a question of training. A fundamental requirement of any electronic travel aid is that it should offer the user upper body protection.