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where specifically noted .

The vehicle characteristics which dominate the

instability modes are the following :

a . There are three wheels . Unless the vehicle is being

operated at constant speed , on level ground , in a

straight line , forces will be encountered which give rise to what I call a " tilt axis , " dictated by geometrical

considerations .

b . Of critical importance is that the line which divides stable

from unstable is abrupt , and the transition is practically

instantaneous .

c . In this geometry , the location of the center of gravity of

vehicle is critical , as is also the center of gravity of the

vehicle operator .

The following types of vehicle accidents can be anticipated as intrinsic

features of the inherent instabilities :

a . Even at standstill , with the vehicle on a side slope ,

at a modest angle , the vehicle will tilt over in

a direction forward and down hill .

b . Even on level ground , with the vehicle turning , and

even going at fairly modest forward speeds , the

vehicle will turn over in a direction forward and

toward the outside of the turn .

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