  In the last years several solutions were proposed to support people with
visual impairments or blindness during road crossing. These solutions focus on
computer vision techniques for recognizing pedestrian crosswalks and computing
their relative position from the user. Instead, this contribution addresses a
different problem; the design of an auditory interface that can effectively
guide the user during road crossing. Two original auditory guiding modes based
on data sonification are presented and compared with a guiding mode based on
speech messages.
  Experimental evaluation shows that there is no guiding mode that is best
suited for all test subjects. The average time to align and cross is not
significantly different among the three guiding modes, and test subjects
distribute their preferences for the best guiding mode almost uniformly among
the three solutions. From the experiments it also emerges that higher effort is
necessary for decoding the sonified instructions if compared to the speech
instructions, and that test subjects require frequent `hints' (in the form of
speech messages). Despite this, more than 2/3 of test subjects prefer one of
the two guiding modes based on sonification. There are two main reasons for
this: firstly, with speech messages it is harder to hear the sound of the
environment, and secondly sonified messages convey information about the
"quantity" of the expected movement.
