Participants were randomly assigned into two six-people
groups (A,B) where group A played the simulator using no
magnitude (NM) and group B using frequency magnitude
(FM). A between-subjects study design is justified to avoid
interference effects, e.g., when participants have mastered
one haptic encoding scheme it may confuse their ability to
learn and use another. We used the same procedure as for
the first study, except subjects were unable to see a display.
Because simulating a temporary blindness with varying durations
at various points in the curve could lead to significantly
different results, and would require a large number of studies
to be performed, we limit our study to steering without
any visual feedback. This provides us with a worst-case performance
in the case a driver is completely blinded, but this
allows for an accurate comparison between both haptic encoding
mechanisms. Participants were instructed on how to
interpret the haptic cues provided for each encoding scheme
and were allowed to try a few roads for practice, to minimize
any learning effects. When subjects felt comfortable
enough, the experiment would start. Participants would drive
each of our eight roads three times in random order. The vehicle
would automatically start driving and at the end of the
straight section teleport to the next road.