to determine when it is "clear to cross"
How do we teach students to look side to side effectively?
We just discussed the challenges that some people have with scanning or glancing from side to side, and strategies for addressing those challenges.
This page explains a procedure for assessing and training students to scan or glance effectively, regardless of the visual impairment.
When training students to detect vehicles visually, their hearing should be occluded because you want to be sure they have the ability to see the vehicles even when it's too noisy to hear them.
Procedure to train students to look for vehicles while scanning / glancing to each side:
This training is done one side at a time.
When the student is skilled at scanning/glancing to look for vehicles approaching from one direction, repeat the entire process for looking in the other direction.
3. When they are ready to try it, have them stand facing the street.
You want to be sure that students are using their vision to detect the vehicles, so it will be helpful to occlude the hearing to make them unable to hear the vehicles.
4. When you give the signal, the students turn to look for vehicles and then look back and report whether there are any vehicles coming.
The students should look as quickly as they can without missing any vehicles (that is, not so quickly that they are likely to miss any).
The instructor should give the signal many times when there is nothing coming, and many times when there is a vehicle or vehicles that will be difficult to see without glancing or scanning properly:
For restricted visual field, the challenging situation is when there is only one vehicle and it's about 2 car-lengths to the left (in the "blind spot").
For central scotoma, the challenging situation is when the only vehicles visible are in the distance (in either direction).
5. If the students miss seeing a vehicle, they should realize they need to improve, and try again:
For the restricted visual field
, scan more slowly.
For the central scotoma, hold the glance a little longer.
Appropriate sites for the training:
This training procedure is best done where there will be lots of opportunities in which the only vehicles approaching are those which would be challenging for the student to see.
This is so that when they say that they see vehicles, it will be easier for you to verify that they actually saw the challenging vehicles if those are the only ones that are visible.
Students with a restricted visual field are challenged to see vehicles in the nearest lane, about two car-lengths to their left (in the "blind spot," as shown in the photo here).
This means you need a place where the street has
only one lane for traffic coming from the left (you want lots of opportunities where the only vehicle approaching from the left is in the nearest lane).
It doesn't matter how many lanes there are for traffic coming from the right.
lots of instances where only one vehicle at a time comes from the left (you want to have lots of opportunities where the only vehicle approaching is in the "blind spot").
Students with central scotoma are challenged to see vehicles in the distance (as shown in the photo here).
Therefore all that's needed are:
visibility of the vehicles from a distance that will be a challenge for the student to see
(that is, nothing should block the view of the distant vehicles);
long gaps in traffic, to give you lots of opportunities where the only approaching vehicles that are visible are in the distance
(that is, there are no vehicles close enough for the student to see easily).
For these students, the number of lanes in the street isn't important.
EXAMPLES OF TRAINING PEOPLE WITH A RESTRICTED VISUAL FIELD
The first example is a video that captured segments of training for a woman who has Retinitis Pigmentosa.
The video is copyrighted by The American Printing House for the Blind (APH) and cannot be reproduced without written permission from APH.
An informal assessment of this woman's vision reveals that she can see an area about 6-8 inches in diameter from about 6 feet away.
After she occludes her hearing with headphones and earplugs, she faces a street that has only one lane coming from the left.
When I saw two cars approaching close from her left in the nearest lane, I tapped her shoulder and she turned to look.
She didn't see either of the cars.
That was a rather dramatic experience, and you can see that when she got the feedback and realized what happened, she improved her scanning immediately.
In all the subsequent trials, she was able to see vehicles that were in the same place where she had missed them earlier.
The second example, shown in the video to the right, is another person with very narrow visual field because of Retinitis Pigmentosa.
I did not occlude his hearing because he is deaf.
He had the same experience that the woman in the first example did, and missed seeing a vehicle because even though he was scanning relatively slowly, it was apparently not slow enough.
You can see that after that experience he scanned even more slowly, and was able to see all other approaching vehicles reliably.
[Click here to read the narration for the introduction.] Note: There's nothing wrong with your viewer -- this video shows a still picture during the introductory narration!
EXAMPLE OF TRAINING A PERSON WITH LOW ACUITY
This video shows segments of training a Deaf man with a loss of visual acuity to scan efficiently for street crossings.
He needed to learn to hold his glance long enough to see the vehicles.