How to operate a wheelchair safely outdoors<br>Stay on even surfaces. Uneven surfaces can make any wheelchair get off balance. Even when someone is pushing a wheelchair, an uneven surface can cause harm.
Unevenness is a reason for balance loss on a wheelchair by, possibly someone pushing it.
( z1 cause :ARG0 ( z2 reason :mod ( z3 usual :polarity - ) ) :ARG1 ( z4 lose :ARG0 ( z5 someone :ARG0-of ( z6 push :ARG1 ( z7 wheelchair ) :ARG1-of ( z8 possible ) ) ) :ARG1 ( z9 balance ) ) )