CROSSINGS WITH NO STOP SIGN OR TRAFFIC CONTROL

Situations of Uncertainty for Gap Judgment
Situations Where You Cannot Be Certain It Is Clear to Cross

SUMMARY: Today, you can be confident that it is clear to cross in many situations,
BUT there are many situations where you can never be certain it is clear to cross.

At some places these situations of uncertainty exist
even when it is very quiet or you can see nothing coming.

The only way to recognize these situations is to
observe and analyze each street-crossing situation.

Our students who cross streets must to be able to RECOGNIZE THOSE SITUATIONS.

What is a "situation of uncertainty for gap judgment"?

Situations of uncertainty for gap judgment -- yesterday and today

If something were coming that would reach you during your crossing, you'd hear/see it!
In these situations, whenever it is quiet (or whenever you see nothing coming), you know it is clear to cross.

some

any

Verified with research

Wall Emerson, R. and Sauerburger, D., 2008

Photo shows a two-lane street that is straight, flat and visible for more than a block.

(left photo)

situation was the same as it had been 60 years ago

WERE

whenever it was quiet, it was clear to cross.

Photo shows a two-lane residential street that bends sharply and disappears less than half a block away.

But at one two-lane residential street (right photo and in the video below), even when it was very quiet, experienced blind travelers with normal hearing were unable to hear some of the approaching cars until the cars were only 4 seconds away!

Four seconds isn't long enough to cross the street, so in that situation
they could never be sure whether they had enough time to cross, even when it is very quiet.

Therefore that was a situation of uncertainty for gap judgment.

Do you want to see it for yourself?

Below: 4-lane crosswalk in front of a high school (10 seconds crossing time) -- see

Vignette #1

Description:

Below:

Description:

How can we recognize if we are in a "situation of uncertainty for gap judgment"?

only

observe and analyze how well you can hear / see the traffic in that situation

A stick figure/person on the corner faces a two-lane street. To the right of the figure (east) the street is straight and goes slightly downhill for about 50 feet and then curves to the left and is visible going straight uphill for another half block.

click here for the "Challenge"

Can we rely on guidelines to identify situations of uncertainty for gap judgment?

Uncertainty Prediction Challenge

And THAT is exactly the point!

THERE ARE NO HARD-AND-FAST RULES FOR FIGURING OUT
WHETHER YOU ARE IN A SITUATION OF UNCERTAINTY FOR GAP JUDGMENT

Sometimes a sharp bend in the road nearby makes it impossible to hear all the vehicles well enough (such as at Photo #3), but sometimes a sharp bend nearby is not a problem (Photo #2).
Sometimes it is possible to hear the vehicles long before they can be seen (such as Photo #2) and sometimes it is possible to see them long before they can be heard (such as at the street in Photo #5 and in the video below).
Sometimes a situation of uncertainty for gap judgment exists even though the traffic is slow (Photo #3), and sometimes even though the traffic is fast it is possible to hear them far enough to know it is clear to cross whenever it's quiet (as shown in Photo #1 and Photo #2).
Sometimes conditions can change so that you can hear the vehicles well enough at one time, but not at another. For example:

When the roads are wet, traffic can be heard better than when they are dry.
A small change at the street in Photo #5 made it possible to hear well enough to know it is clear to cross whenever it is quiet (see "Environmental Modifications").
Parked vehicles created a situation of uncertainty for gap judgment because they blocked the sound of traffic at the street in Photo #6. And yet in our research, when we placed a barrier between blind participants and the traffic (see photo), it didn't seem to impair their ability to hear the vehicles significantly (Wall Emerson & Sauerburger, 2008). So the presence of something that might block the sounds is not a reliable indicator as to whether there is a situation of uncertainty for gap judgment either.

We don't know all the conditions that can affect the sound:

click here

how quiet or noisy the conditions were when the blind participants first heard the vehicle;
the sound level of the vehicle itself and its speed; and
the presence of blockage or hills / bends in the road.

these factors altogether

"...need to be aware that before they can assume that it is clear to cross when quiet in a given situation,
they must first observe their ability to hear the vehicles in that situation and
determine whether they can hear well enough to know that it is clear to cross."
(Wall Emerson, R. & Sauerburger, D., 2008, page 760)

Example of misleading situation -- impossible to predict!

...the ONLY way to determine if a situation is uncertain for gap judgment is to

observe and analyze how well you can hear / see the traffic in that situation

(right, below)

So what? How does this affect what we Orientation and Mobility Specialists teach?

best practice is for O&M instructors to teach their students to be able to recognize situations of uncertainty for gap judgment

position paper

the traditional strategy for crossing streets with no traffic control ("assume it is safe to cross when quiet") is no longer dependable;
O&M programs must ensure that consumers who are blind or visually impaired are able to
- determine whether they can recognize gaps in traffic that are long enough to cross, and
- determine the level of risk for crossing (including the likelihood that vehicles could reach them and the likelihood that drivers will yield to them).

Thus it becomes incumbent upon us to follow established best practice and address these issues with our students, teaching them the skills and concepts they need to deal with modern crossings.

So, how can we teach our students about crossing with no traffic control?

How can we teach our students to recognize situations of uncertainty for gap judgment when there are no reliable guidelines other than careful observations and analysis of their ability to hear or see the vehicles in each situation?

I have been working on this problem with my students for 20 years. During this time, my understanding of the issues has slowly evolved, and so have my instructional strategies, explained in Journey to Understanding (to find out what inspired this work, click here).

For a list of all the skills that seem to be necessary, as well as suggestions for teaching them . . .

Go to "Teaching students to recognize Situations of Uncertainty." (Section 2 of the Self-Study Guide)

Wall Emerson, R. & Sauerburger, D (2008). "Detecting approaching vehicles at streets with no traffic control." Journal of Visual Impairment and Blindness, AFB Press, Volume 102, Number 12, pp. 747-760

This webpage was developed from a poster that was graciously hosted on the SpEdEx website --
my heartfelt appreciation to SpEdEx webmaster Ray Dragon!

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