December, 2022: Vision Rehabilitation International. Volume 13, Issue 1 https://sciendo.com/article/10.2478/vri-2022-0001
reproduced under the Creative Commons Attributions-NonCommercial-No Derivatives 4.0 International Licence (CC-BY-NC-ND 4.0)
Teaching students to recognize and deal with
Situations of Uncertainty at uncontrolled crossings
Jolene Troisi and Dona Sauerburger
Abstract
A significant aspect of Orientation and Mobility is teaching travellers with visual impairments systematic methods to access their environment and evolving these methods to match the complexity of the world around us. At crossings where there is no traffic signal or stop sign, there are increasingly many situations where it is no longer best practice to assume it is clear to cross when quiet, or simply re-route and avoid. This article explains a step-by-step method O&M specialists can use for teaching travellers with visual impairments how to determine if a crossing is a “Situation of Uncertainty” or a “Situation of Confidence” by helping them develop an intuitive understanding of their own crossing time; learn to intuitively and accurately compare their crossing time with the warning time of approaching vehicles; and judge whether or not they can be confident that it is clear to cross whenever it is quiet in that situation. Following this, the article discusses a method that learners can use to determine the level of risk at any given crossing so they can decide if the level of risk is acceptable or unacceptable to them.
Introduction
Amid the ever-increasing complexity of navigating
pedestrian travel, it is important that our Orientation
and Mobility curriculum includes teaching travelers
with visual impairments (hereafter referred to as the
“student”) to cross streets with no traffic signal or
stop sign using the most up-to-date methods. This
article explains a step-by-step method O&M
Specialists can use for teaching students how to
determine if they have enough warning of
approaching vehicles to be confident it is clear to
cross whenever it is quiet, rather than following the
inaccurate assumption that “all-quiet” is
synonymous with “all-clear” or “safe”. This can be
done by helping them develop an intuitive
understanding of their own crossing time; learn to
intuitively and accurately compare their crossing
time with the warning time of approaching vehicles;
and judge whether or not they can be confident that
it is clear to cross whenever it is quiet in that
situation. Consistency is encouraged with the use of
a flowchart (Figure 1) when analyzing situations.
Students are also provided with a guideline to help
determine the level of risk of crossing in Situations
of Uncertainty and decide if they are willing to
accept that risk.
At crossings with no traffic signal or stop sign, such
as at intersections with stop signs for one street but
not the other, and at roundabouts and channelized
right-turning lanes, there are many situations
where, even when it is quiet, the approaching
vehicles cannot be heard with enough warning for
people to be confident that it is clear to cross (Wall
Emerson and Sauerburger, 2008). For example, if
people need 7 seconds to cross a given street or
lane and they cannot hear approaching vehicles
when it is quiet until those vehicles are less than 7
seconds away, they cannot be confident that it is
clear to cross because even when it is quiet, there
could be an undetected vehicle approaching that
could reach them during their crossing. These
situations are called situations of uncertainty of gap
judgment (Barlow, Bentzen, Sauerburger, & Franck,
2010) – we will refer to them here simply as
“Situations of Uncertainty.” People who use their
vision at crossings with no traffic control are also in
Situations of Uncertainty when they cannot see
approaching vehicles with enough warning to be
confident that it is clear to cross. Situations where a
person CAN hear (or see) all approaching vehicles
with enough warning to be confident it is clear to
cross whenever it is quiet (or when no vehicles are
visible) are called Situations of Confidence.
Often, the vehicles can be heard with enough
warning when approaching from one direction but
not the other. For example, the time needed to
cross and get out of the way of vehicles
approaching in the nearest side of the street is
usually half the time for getting out of the way of
vehicles coming from the other direction, so the
warning time needed for vehicles in the first half of
the street is less. And sometimes there is a hill or a
bend in the road that blocks the sound of vehicles
coming from one direction but not the other. When
the warning time for vehicles approaching from one
direction is insufficient, the crossing presents a
Situation of Uncertainty regardless of whether
vehicles coming from the other direction are heard
or seen with enough warning.
It is important that our O&M curriculum includes
teaching students to recognize Situations of
Uncertainty and be able to analyze the risks of
crossing in these situations. And because the
situation at a given crossing can change from day
to day and sometimes even minute to minute,
whenever people plan to cross where there is no
traffic signal or stop sign, they should take some
time to observe and judge whether it is a Situation
of Uncertainty at that time. For efficiency and skill
generalization, this judgment should be made
readily, without having to use any formal
assessment with counting or timing. Following is a
brief outline of a systematic method for teaching
students to recognize Situations of Uncertainty, and
analyze the risk of crossing in these situations.
Process for teaching students to recognize Situations of Uncertainty
The process for training described in this article can
be used by students of all ages who are ready to
begin learning concepts and skills needed for
crossing streets. It is best to provide this training
after the student understands how vehicles move at
uncontrolled crossings and the concept of crossing
when they can be confident that it is clear to
cross. This includes understanding that to be
confident that it is clear to cross, there needs to be
sufficient warning of approaching vehicles detected
by either their auditory or visual sense. Once
students are ready for the training, the following
step-by-step process can be used for teaching them
to recognize Situations of Uncertainty.
First step: Help students develop an intuitive understanding of their own crossing time.
To be able to recognize Situations of Uncertainty
readily, students need an intuitive understanding of
the time they need to cross streets. The following
explains the process for developing an intuitive
understanding of the time needed for crossing a
street; this process should be adapted for helping
students also develop an intuitive understanding for
crossing half of that street, as well as streets of
different widths.
After students have had the opportunity to
cross the street, tell them that you are going to
demonstrate the time needed for their crossing.
Start by asking them to imagine crossing the street,
beginning when you start a stopwatch.
When the stopwatch indicates that the time
which students need to cross has passed, tell them
that is when they would have reached the other
side. For example, if their crossing time is 7
seconds, have them imagine starting to cross the
street while you start a stopwatch. Seven seconds
later, tell them they would have reached the other
side at that time.
Next, ask students to imagine crossing the
street again, but this time have them report to you
when they start their imaginary crossing, and when
they think they would have reached the other side.
Make sure they are actually imagining the crossing,
not counting
Start a stopwatch when students report that
the imaginary crossing has begun and stop
the watch when students report that they
think they would have reached the other side.
ll students whether they were accurate.
For example, if a student needs 7 seconds to
cross and only 5 seconds have passed from
when they started their imaginary crossing
until they say they imagined that they have
reached the other side, tell them that they
needed more time than they thought they did.
Students who are having difficulty estimating
the time may benefit from having you
demonstrate it again until they are ready to
try it themselves.
This exercise continues until students can
consistently estimate when the time needed to
cross the whole street has passed (give or take a
second). The process should be repeated for
developing an intuitive understanding of the time
needed for crossing half the street. Most people can
learn this in 5-10 minutes.
Second step: Help students learn to
intuitively compare the crossing time with
the warning time of approaching vehicles
accurately.
While standing at the edge of the crossing,
have students wait until it is quiet. If there is a
steady ambient sound that is considered part of the
conditions of that situation (such as the sound of an
air conditioner or fountain), “quiet” would mean
there are no temporary extraneous noises that
could mask the sound of the approaching vehicles.
If students are using their vision, have them wait
until they can see no approaching vehicles (that is,
it appears to be clear).
Once it is quiet / clear, have students listen
or watch for traffic, and report the first detection of
something that they think might be an approaching
vehicle. Explain that they should not wait until they
are sure it is a vehicle before they report that they
think they heard (or saw) something coming. Tell
them that once the vehicle passes, they should
report whether they think the warning time of the
vehicle (the time from when they detected it until it
arrived) is longer than, shorter than, or about the
same as the time they need to finish crossing the
street (or that part of the street)
If they are using their hearing, they can report
when they think they hear a vehicle
approaching from either direction. If they are
using their vision, they should look in just one
direction at a time and assess the situation
from that direction, then turn and assess the
situation from the other direction. They may
need training later to be able to efficiently
look for vehicles from one side to another
(Fazzi and Barlow, 2018, Barlow, Bentzen,
Sauerburger and Franck 2010).
Once students report that they suspect that
they hear (or see) something that might be an
approaching vehicle, start a stopwatch and ask
them if it was quiet when they heard that vehicle. If
they think it was quiet and you think it was not, they
may need some further training to be aware of what
“quiet” means.
Regardless of whether it was quiet when they
heard the vehicle, continue timing its
approach and stop the watch when it passes
in front of the student. Do not report the time
until after the student guesses whether the
warning time was longer than their crossing
time.
After the vehicle passes, ask students to
guess if the warning time (detection-to-arrival time)
for that vehicle was shorter than, longer than, or
about the same as their crossing time for that part
of the street. For example, if the vehicle was
approaching in the first half of the street, students
need to guess whether the warning time for that
vehicle was longer than / shorter than / about the
same as the crossing time for that half of the street.
If the vehicle was approaching in the last half of the
street, students compare the warning time of that
vehicle with the time needed to cross the entire
street.
Tell students if they were correct.
Repeat until students can accurately judge
whether the warning time was longer than, shorter
than, or about the same as the time they need to
cross in front of vehicles coming from that direction.
NOTES:
1. If it was not quiet when they reported
hearing an approaching vehicle, after they
guess whether the warning time was longer
than their crossing time, tell them whether
they were correct or not. Then explain that
since that vehicle was not heard when it is
quiet, it cannot be used as a sample to help
them determine if approaching vehicles are
heard with enough warning time when it is
quiet. If it was heard with less warning than
other vehicles, it is a terrific opportunity to
discuss the effect of masking sounds
making vehicles harder to hear and
reducing their warning time.
2. If they report hearing a vehicle when it is
quiet but there is no vehicle approaching,
praise them for reporting that something
might be coming, and reset the watch to
wait again for a vehicle. If you do not
acknowledge or praise their reporting, the
next time they may not report as soon as
they think there might be a vehicle coming,
and instead will wait until they are more
certain.
Third step: Have students conclude
whether this is a Situation of Uncertainty.
Once students have sampled the warning times of
enough approaching vehicles, they can determine
whether they are in a situation where they can be
confident that it is clear to cross whenever it is quiet
(or whenever they see no vehicles approaching), or
a Situation of Uncertainty. They should be aware
that they are not assessing the crossing once for all
time, they are merely assessing the situation that
exists for the crossing at that moment, and
situations can change drastically at each encounter.
If students were not able to sample enough vehicles
that approached when it was quiet (either because
it never got quiet, or because there were not
enough vehicles), they are, by definition, in a
Situation of Uncertainty - they cannot be sure that it
will be clear to cross whenever it gets quiet (or, if
they are using their vision, it may not be clear to
cross whenever they see no vehicles approaching).
Once they have sampled enough vehicles that
approached when quiet, they can use the following
flowchart to determine whether they are in a
Situation of Uncertainty. For vehicles approaching
in the first half of the street, and for vehicles
approaching in the last half of the street, they need
to ask themselves:
Was the warning time of any vehicle shorter
than the crossing time for that part of the street?
If YES, then this is a Situation of Uncertainty
for vehicles approaching from that direction.
If NO, then consider the range of warning
times:
Was the range of warning times close to the
crossing time? That is, was the warning time of any
of the vehicles close to the crossing time?
If YES, then this is a Situation of Uncertainty
for vehicles approaching from that direction.
If NO, then consider the spread of the range:
Was the spread of the range of warning
times broad? For example, a range of warning
times being 12 to 25 seconds is broad, whereas a
range of 12-15 seconds is not.
If YES, then this is a Situation of Uncertainty
for vehicles approaching from that direction.
If NO, then this is a Situation of Confidence
for vehicles approaching from that direction.
In other words, you can be confident that it is clear
to cross when quiet if the range of warning times
sampled is narrow and not close to the crossing
time.
If there is a Situation of Uncertainty for vehicles
from either direction, it is a Situation of Uncertainty
for the crossing at that time. That is, a Situation of
Confidence exists only when there is a Situation of
Confidence for vehicles from both directions
Make sure students realize that crossings that
present a Situation of Confidence at one time may
present a Situation of Uncertainty at another. When
a crossing outside of Philadelphia where a blind
man and his guide dog were killed in 2010 was
analyzed a few weeks after his death, it was a
Situation of Uncertainty on a Friday afternoon, but a
Situation of Confidence on a Saturday evening. If
he had analyzed the situation and its risks before
starting to cross, he might have decided the risks
were not acceptable, and crossed a few blocks
away where an accessible pedestrian signal had
been installed at his request.
Figure 1: Flowchart: Is this a Situation of Uncertainty?
Fourth step: Repeat this procedure at a
variety of uncontrolled crossing situations
until students can consistently draw
accurate conclusions and determine if they
are in a Situation of Uncertainty or
Confidence.
This phase of training involves taking students to a
variety of crossing situations and asking them to
listen (or watch) for approaching vehicles and judge
whether it is a Situation of Uncertainty or a Situation
of Confidence, based on whether the warning times
of approaching vehicles from both directions are
longer than their crossing time. This is best done at
crossings where there is intermittent traffic, such
that there are plenty of times when it is quiet, and
plenty of times when vehicles are approaching.
Students using their vision will assess the
situation in each direction separately. That is, they
analyze their detection of vehicles in one direction
until that assessment is complete, then they turn
and do the same for traffic coming from the other
direction. It is essential that they develop strategies
to look from one side to the other efficiently to make
sure it is clear in both directions (Fazzi and Barlow,
2018, Barlow, Bentzen, Sauerburger and Franck
2010) - these strategies are explained by
Sauerburger and Bourquin (2020) and should be
addressed after the students have learned to
assess whether there is a Situation of Uncertainty in
either direction, assessing one direction at a time.
Assessing Risk of crossing in Situations of
Uncertainty
When students find themselves in a Situation of
Uncertainty, their first step is to assess the risk of
crossing. If they cross in these situations, they will
be crossing when there may be approaching
vehicles that would have to slow down or even stop
to avoid hitting them, so to assess the risk of
crossing they need to find out:
1) whether they have the right of way there,
2) how likely they will be surprised by an
undetected vehicle that could reach them
during their crossing and if that happens,
3) how likely it will hit them, and
4) if they are hit, how likely they would be
seriously injured or killed.
Students should be familiar with the pedestrian laws
in their community to know whether they are risking
being hit by a driver who has the right of way. The
likelihood that they would be surprised by an
undetected approaching vehicle depends on traffic
volume and how well they can detect the
approaching vehicles. If there is very little traffic,
and they can hear the approaching vehicles with
almost enough warning then it will be much less
likely there is an undetected vehicle that could
reach them during their crossing than if there are
lots of vehicles there, and they cannot be heard
until just before they reach the crossing.
There are several factors to consider when
determining the chances of a vehicle hitting them if
it approaches unexpectedly during their crossing. If
the visibility and road conditions are good, they are
using a cane, and drivers are going slowly and
expecting pedestrians, then the likelihood that they
would be hit is less than if the roads are slippery
and it is difficult for drivers to see them, they are not
using a cane and are crossing where pedestrians
are not expected, and the traffic is traveling fast. In
addition, if there is more than one lane for
approaching vehicles in either direction, there is the
possibility of “multiple-threat collision,” where one
vehicle stops for a pedestrian and drivers in other
lanes cannot see the pedestrian until it is too late
for them to stop.
If pedestrians are hit, the likelihood that they would
be seriously injured or killed would depend on the
speed of the vehicle. For example, there is about a
20% chance of being seriously injured or killed if hit
by a vehicle going less than 32 kilometers/20 miles
per hour, and this likelihood increases to 70% if the
vehicle is going faster than 73 kilometers/ 46 miles
per hour (NHTSA 1999).
Our students should be able to take all these
factors into consideration and determine how likely
it is that if they cross in that situation with those
conditions, they will be surprised, hit, and seriously
injured by a vehicle that was undetected when they
began their crossing. If the risk of this happening is
not acceptable, they need to be able to implement
alternatives to crossing in this situation, such as
getting assistance, crossing somewhere else,
avoiding the crossing altogether by getting a ride or
choosing not to go to that destination at that time,
etc. Different students will have different levels of
acceptable risk, this process of analysis is designed
to help them determine what they are comfortable
with in a systematic way that encourages conscious
decision-making based on objective observations of
the key factors.
Examples
The following examples were written by an
instructor teaching two adults about uncontrolled
crossings, one of whom was at a Situation of
Uncertainty, and one at a Situation of Confidence:
Example 1: Recognizing a Situation of
Uncertainty, and analyzing the risks
The student was at a residential intersection of two
streets that had stop signs for one of the streets,
but not the other. She had just learned how to cross
the street with the stop sign, and we now turned
and talked about how to cross the other street. She
said she’d want to cross it when no traffic is coming,
and she learned that she could be confident that no
traffic is coming whenever it is quiet only if she has
enough warning of approaching vehicles, so we
started to analyze whether or not she had enough
warning of the vehicles in that situation.
First, we timed her crossing. I asked her to cross
the street several times when I said it was clear; her
first crossing took 10 seconds and the second took
13, so her crossing time was 13 seconds. After she
spent about 5 minutes developing an accurate
intuitive understanding of her crossing time, I asked
her to wait till it was quiet, then report when she
heard something that might be a vehicle
approaching.
However, when she said it was quiet, I could still
hear receding car sounds, and then she said she
thought she heard a car. Three seconds later the
car arrived, and she correctly guessed that it wasn’t
enough warning time for that car. I helped her
understand that she didn’t know whether she would
have heard it with enough warning if it had been
quiet when she had heard it. So, we waited until we
agreed it was quiet, and then listened again for
approaching vehicles.
When she reported she thought she heard
something that might be a car, I started the timer,
and stopped it when the vehicle passed our
crosswalk. Without telling her that it was 7 seconds,
I asked her if there was enough warning of that
vehicle’s approach. She correctly said no. Then I
asked her how far she would have gotten by the
time it arrived if she had started just before she
heard it (while it was still quiet). Again, she was
correct when she said she’d be about halfway
across.
At that point, we could conclude that in that
situation, she could not be confident that it was
clear to cross whenever it was quiet - she was in a
Situation of Uncertainty. We then used the checklist
“Risk Analysis for Situations of Uncertainty” to
determine how likely it would be that a vehicle
would be coming when she started to cross and if
that happened, how likely she’d be hit and seriously
injured or killed.
Evaluating the items on the checklist, we decided
that whenever it was quiet
(1) it was moderately likely that there would be a
vehicle approaching because traffic volume was
moderate, and she was unable to hear some of
them till they were fairly close;
(2) if an undetected vehicle was approaching as
she started to cross, it was moderately likely that it
would hit her because, even though road conditions
were good and drivers might expect pedestrians
there and she would be using a white cane, it was
difficult for drivers to see her and they were going
moderately fast;
(3) if the vehicle did hit her, there was a 42%
chance of being seriously injured or killed (traffic
was going at about 30-50 kmh / 25-30 mph).
She decided that the risk was not acceptable, and
we considered alternatives.
Example 2: Recognizing a Situation of
Confidence, and the effect of masking
sound
The lesson took place at a residential intersection
with no stop sign for the street we were analyzing.
We had determined that his crossing time was 7
seconds and he had developed an intuitive
understanding of that crossing time. We began to
analyze the situation to determine whether there
was enough warning from approaching vehicles for
him to be confident that it’s clear to cross when
quiet.
Like the first student, he reported hearing a car
when it was not quiet, and correctly guessed that it
did not give enough warning. I then asked him if
was quiet when he heard it, and after thinking for a
while, he said there were sounds of receding cars. I
explained that the sound of receding cars can
significantly mask the sound of approaching
vehicles, so we did not know yet whether or not he
could hear them with enough warning when it’s
quiet. So, he waited till it was quiet, and then
reported when he thought he heard something that
might be another vehicle, and I started the timer.
I stopped the timer when the car passed us and,
without telling him that it was 15 seconds before the
car arrived, asked if it was enough warning. He said
it was, and I told him it was 15 seconds - we
laughed, saying he’d have enough time to cross
and come back and have a cup of coffee. As we
talked, another car approached but we didn’t hear it
until it was just a few seconds away, and I asked
why we could hear the other car so far away but not
this one. He said the car we had timed was still
receding, and masked the sound of the other car.
We started listening again and I asked several
times if it was quiet yet. He kept saying no, and just
as I heard the last sound die away, he said it just
became quiet. Throughout the lesson, I kept asking
whether it was quiet until I became convinced that
he could recognize masking sounds and know
when it is actually quiet.
Once, when we listened while quiet, he reported
hearing something that might be a car, and I started
the timer and thanked him, saying I was so glad he
was not waiting to be sure it’s a car before reporting
that he heard it. It turned out not to be an
approaching vehicle so I reset the timer and
thanked him again and he resumed listening.
The warning times for the next few vehicles heard
from the left when quiet were 21 and 22 seconds,
and another from the right was heard 22 seconds
away, I asked him if he felt that was enough
samples to feel confident he has enough warning.
He said yes, although he said the situation could be
changed with environmental noises, and I agreed,
adding that even the ambient sound level of “quiet”
can change dramatically during the day. So we
affirmed that his conclusion only applies to this
moment in time.
I then asked him why he could feel so confident that
it would be clear to cross whenever it was quiet,
given that we only had a few samples of vehicles
approaching when quiet. After some prompting, he
explained that it was because the warning times
were all more than twice as long as he needed, and
the range of samples was relatively narrow, so it
seemed extremely unlikely that whenever it was
quiet, a vehicle could get too close without his being
able to hear it.
Summary
The goal of this training is for travelers with visual
impairments to demonstrate that they can correctly
determine if they can be confident that it’s clear to
cross when quiet when presented with a variety of
crossing situations that include at least one
Situation of Confidence and one Situation of
Uncertainty; analyze the risks of crossing in each
Situation of Uncertainty; and implement alternatives
if the risk is not acceptable. As with any O&M skill,
students should practice this method repeatedly
with supervision in a variety of situations and
environments before they can be deemed to be
using the methods effectively and proceed to
independent use when traveling alone.
Further details, checklists, considerations, and
suggestions about this process with illustrations and
videos are in the “Self-Study Guide: Preparing Visually
Impaired Students for Uncontrolled Crossings” at
www.sauerburger.org/crosscredit. Another resource is the
software program “Crossings with no Traffic Control:
Teaching Concepts and Skills to Deal with Them,”
developed by Dona Sauerburger with the American
Printing House for the Blind (www.aph.org). It provides
simulation experiences and information to help O&M
instructors teach these skills.
Conflict of Interest:
The authors have no conflicts
of interest to disclos
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