Electric Wheel Chair

 "Hello, this is Shlomo Zalman speaking." When Rabbi Yisrael Rozen, the Dean of the Zomet Institute, first heard this on the phone, he didn't realize who was on the line, but after the speaker repeated his name Rabbi Rozen recognized the voice of the well known Torah scholar, Rabbi Shlomo Zalman Auerbach (who has unfortunately passed away since then). Rabbi Auerbach, one of the leading halachic authorities of the previous generation, was an expert on the halacha of electricity and technology.

 Rabbi Auerbach invited Rabbi Rozen to join him on a visit to a handicapped woman who regularly used a wheelchair. In fact, the need was not so "urgent," since her family was able to help her move around. But because of her strong desire to be independent – especially to be able to leave her home on Shabbat – she asked the rabbi to find a way for her to use her electric wheel chair on Shabbat. And Rabbi Auerbach was able to help her!

 The goal was not only to let a woman go to the synagogue (which she is not really obligated to do) but also to improve her "quality of life" in general. The rabbi's ruling is suitable even for people whose family members are available to push them around on Shabbat, since a handicapped person who must be pushed loses the relative freedom that he or she has with an electric wheelchair. The novelty of the ruling is that it is based on both halachic and technological factors, in that it considers a handicapped person as a "sick person not in mortal danger who is suffering in his entire body." This status means that under certain conditions rabbinical decrees are not in effect, especially when using the principle of gramma (indirect action) as explained below.

 How does the electric wheelchair designed by The Zomet Institute differ from other wheelchairs?

 First, the motor is turned on using the principle of gramma. Because of the way the system works the chair will "crawl" forward even when the rider does not want to move, moving slowly in such a way that it can be stopped by mild friction. If the chair would be lifted into the air the wheels would be constantly turning. Usually a rider's weight is enough to keep the chair motionless. It is possible to set a mechanical brake or to stop the chair in order to avoid an obstacle, and then it will stand in place in spite of its tendency to "crawl."

If the rider wants to move, what he or she does is to change the level of the current without switching on a new electric circuit (which would be a violation of the prohibition of "building" on Shabbat). The chair is stopped using the same principle: the rider decreases the current but does break the electrical circuit.

 When the ride is over, the current is turned off using a gramma switch.

 A sign on the wheelchair declaring that it is under "Shabbat Control" avoids any possibility that the rider will be accused of sin, and this is almost as important as the mechanism itself. It provides a protective envelope which declares that the use of the wheelchair is halachically permitted according to prominent experts of our generation.

Can the Shabbat wheel chair be used outside of an eruv?
This is indeed a problem.
There are rabbis that permited this and the main reason given is that the wheel chair for the disabled can be considered like a garment, shoe or accessory belonging to a person's body.
For more details  you can read the letter correspondence (Hebrew) between several rabbis on this issue.
It's advised to consult with the local rabbi about this issue.

For more Halachic details: 
    ♦ The Electric Wheelchair on Shabbat,Rav Yair Meir, Crossroads 3 P.97
     ♦ The Freedom of Mobilty - Halachic Adaptation of Electric Mobility Devices for Use on Shabbat and Holy Days by Rabbi Yisrael Rozen, Engineer, Dean of Zomet Institute