Segway, Inc., notified consumers of a voluntary recall in mid-September of its Personal Transporters &#151 two-wheeled vehicles that use the same gyroscopic balancing technology as the stair-climbing iBOT power chair from Independence Technology/Johnson & Johnson.

According to the U.S. Consumer Product Safety Commission (CPSC), approximately 23,500 commercial and consumer units &#151 the total number of units sold thus far &#151 are involved in the recall. A statement from Segway said the vehicle “can unexpectedly reverse the direction of the wheels, which can cause the rider to fall.” The CPSC said Segway has received reports of head and wrist injuries from riders involved in such falls.

Segway, with corporate headquarters in Bedford, N.H., instructed owners to stop using the vehicles and to contact the manufacturer for a free software upgrade.

This is Segway’s second recall. The first, in Sept. 2003, was a voluntary recall of approximately 6,000 units due to danger of some riders falling when the battery charge was low.