How
people who are blind or visually impaired cross streets
Traditional techniques Techniques and cues used in crossing streets
are diverse and vary by the type of location and by the individual and
his or her level of vision. Individuals who are blind or visually impaired
often travel to unfamiliar areas and intersections and gather information
from available sources.
Detecting the street The first information needed by pedestrians who are blind is "Have
I arrived at a street?" People who are blind or visually impaired
use a combination of cues to recognize the street edge. These may include:
Curb or the slope of the ramp
End of building line and open sound of the intersection
Sound of traffic on the street beside them (the parallel street)
Sound of traffic stopping on the street they are approaching (the
perpendicular street)
Presence of pedestrians
Presence of an intersecting sidewalk
Identifying the street
The next information needed for decision-making at unfamiliar intersections
is: "Which street is this?"
This information is only occasionally provided in any accessible
format.
Pedestrians who are visually impaired develop a mental map and keep
track of where they are within that map, usually by counting blocks
and street crossings.
Where necessary, and available, assistance may be sought from other
pedestrians.
Analyzing intersection geometry The next information needed is: "What is the geometry of
this intersection?" including:
Is my destination curb straight in front of me, or must I angle
to the left or right to reach it?
How many streets intersect here?
How wide is this street?
Should I expect to encounter any islands or medians as I cross this
street?
Am I standing within the crosswalk?
This information may be immediately available to pedestrians having full
vision, but it may not be possible for pedestrians who are blind to determine
this information by listening to traffic patterns. Incorrect or missing
information for any of these questions may result in missing the destination
curb or median.
Analyzing the traffic control system Next, pedestrians with visual impairments need to identify
the type of traffic control system at this intersection:
Is this a signalized intersection?
Do I need to push a button to actuate the Walk interval? If so, where
is the button?
Is the button close enough to the crosswalk that I will have time
to position myself correctly at the crosswalk, facing my destination
curb, before the onset of the Walk interval?
Which button controls the Walk interval for the street I want to cross?
Does it stop traffic on one street, or all traffic?
Do cars still turn during the Walk interval?
Is there a second button on the median that I must push?
Will there be a surge of parallel traffic telling me the Walk interval
has begun? Will I be able to hear it over other, concurrent traffic
sounds?
Techniques for gathering this information include listening to traffic
patterns through several light cycles, and searching the sidewalk area
for poles with pushbuttons. This task has become difficult or impossible
at many intersections. Missing information for any of these questions
may result in failure to use pedestrian push buttons and crossing at times
other than the pedestrian phase.
Identifying the crossing interval
After determining the geometry of the intersection, aligning to face towards
the destination curb, determining that the intersection is signalized and
having pushed a button, where necessary, pedestrians who are blind need
to know: "When does the Walk interval begin?"
In the most common technique utilized for crossing at signalized intersections, pedestrians who are blind begin to cross the street when there is a surge of traffic on the street parallel to their direction of travel.
Maintaining crossing alignment Once the pedestrian who is blind has begun to cross the street,
the next question is: "Am I headed straight towards my destination
curb?"
Traffic going straight ahead on the parallel street provides helpful auditory guidance to many persons if it is present. In addition, pedestrians who are blind may use traffic waiting on the perpendicular street as a partial alignment cue.
Turning traffic can make it difficult to hear and align with the traffic traveling straight through the intersection.
In the absence of traffic on the parallel street, pedestrians who are blind are more likely to veer toward or away from the intersection.
