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Developments in Electronic Mobility Systems

John Gill
Chief Scientist, Royal National Institute for the Blind


Over the last thirty years considerable effort has been devoted to developing electronic systems to help blind pedestrians with mobility and orientation.  However blind people have seen little practical benefit from all this activity, but within the next ten years there are likely to be significant advances which will bring practical benefit at affordable prices.

Electronic Obstacle Detectors
These devices often work in a similar way to radar, in that they send out a pulse and time how long it takes to bounce back from the nearest object.  In devices for blind pedestrians, the pulses are usually ultrasonic, laser or infrared.  The output to the user can be auditory or vibratory.  Audible output has the disadvantage that it tends to mask other sounds which the user may want to hear.  Vibratory output can only communicate a relatively small amount of information to the user; this is not a severe limitation in a basic obstacle detector.

These detectors provide information about obstacles at a greater distance than can be detected by a long cane, and they can warn of obstacles at head height.  However all these devices have problems in reliably detecting a single step down.  The more sophisticated devices may provide so much information about the environment that the user suffers from information overload.  In the next few years research is likely to concentrate on the automatic processing of the data so that only relevant information is provided to the user.

Information Systems
These systems give you information at a specific location, such as at the entrance to a building.  This information is normally in the form of a speech message.  It is possible to trigger an audible message whenever somebody approaches the location, but this can cause a nuisance for those who do not need it.  The alternative is to use short-range infrared or radio signals, and the blind person carries a small receiver.  This type of system can be used for giving the destination of buses or the next train.

A different approach is to use a contactless smart card or electronic tag which triggers an audible message from the terminal at a distance of a few metres.  In this case the message comes from the terminal rather than from a device carried by the blind person.  This type of system can help a blind person locate the terminal.

All these information systems require a considerable financial investment to install and maintain the infrastructure.  Therefore, despite a very large number of successful pilot schemes, none of these systems has come into widespread use.

Positioning Systems
In the last few years there have been dramatic developments in systems for helping military personnel accurately find their position using satellites.  This technology is now being used by civilians for locating the position of vehicles.  In its civilian version, the American global positioning system gives an accuracy of about 100 metres as long as the user has line of sight to at least three of the satellites.  This accuracy can be improved to about 2 metres using an extra signal which, in Britain, is broadcast by Classic FM radio.  For a car driving down a road, the line of sight limitation is not a major problem since if the car goes under a bridge or in a tunnel, this is usually for a short period of time.  However blind pedestrians often walk on pavements close to tall buildings, so typically they will only receive an accurate position about 75% of the time. 

Another possible technology uses the relative strengths of signals at the base stations used for mobile telephony.  This approach currently gives an accuracy of about 100 metres, but considerable effort is being devoted to improving this accuracy.

Both these systems have the advantage that the infrastructure has been installed for the general population, and so does not have to be paid for from the limited funds available to support the blind community.  However more work is needed before these systems will be of practical benefit to blind people.

Route Planning Systems
Traditionally blind people have used embossed maps, but their availability has been very limited and the quality variable.  Now there are other possibilities in the form of electronic maps.  Ordnance Survey have precise electronic maps of the whole of the UK which include details such as house numbers and position of pedestrian crossings.  Therefore a blind person could have a simple computer system with speech output which permits them to plan routes or explore an area.

Ideally extra information could be added to these maps such as associating a bus timetable with a bus stop.  The collection and input of such extra information might be a task that could be undertaken by volunteers.

The Future
Electronic obstacle detectors need to significantly improved before they achieve widespread acceptance among the blind community, but ongoing research encourages the hope that within ten years these devices will be significantly more user friendly.

With information and positioning systems, the major problem is one of finance; the current emphasis on adapting systems already installed for sighted people so that blind people can use them appears to be promising.  Also the use of the mobile telephony infrastructure could lead to practical inexpensive systems.

Route planning systems appear rather mundane in comparison to satellite navigation systems, but offer the possibility of being available at reasonable prices in the foreseeable future.



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