Table of Contents(Page links take you to the website pages)

Section 4 : Teaching students to determine when there is a crossable gap in traffic Page   1:  Skills needed to determine when it's "clear to cross" Page   2:  USING HEARING -- Know what to listen for and "tune in" to the sounds Page   3:  USING HEARING to determine when it's quiet enough to be "all clear" -- is this skill necessary? Page   4:  USING HEARING -- Teaching students to determine when it's "quiet enough," and understand the effect of masking sounds Page   5:  USING VISION -- Visual tasks for crossing streets Page   6:  USING VISION for "all clear:" Knowing what to look for, and seeing them efficiently/reliably Page   7:  USING VISION for "all clear:" Looking left/right -- challenges and strategies with different eye conditions Page   8:  USING VISION for "all clear:" Procedure to train students to look for vehicles while scanning / glancing to each side Page   9:  USING VISION -- When you see traffic at a distance -- do you have time to cross? Page   10:  USING VISION -- is traffic far/slow enough? "Determining Gaps in Approaching Traffic" (was "TMASD") Page   11:  USING VISION -- How to determine how many seconds is "X" seconds? Page   12:  USING VISION -- ALTERNATIVE when you cannot judge whether the traffic is far/slow enough to allow you time to cross Page   13:  USING VISION -- Determine when the traffic is far/slow enough by SCANNING or GLANCING left/right Page   14:  USING HEARING OR VISION -- Which is better to determine when it is clear to cross? Page   15:  USING HEARING OR VISION -- Teaching students to choose vision or hearing to detect vehicles Page   16:  Review 

Please note that the links inserted throughout the text are NOT necessary, they are meant only for those who want to know more.

Section 4:Teaching students to determine when there is a crossable gap in traffic

So far, we have talked about: what is a Situation of Uncertainty and how to recognize it (Section 1); teaching students to recognize Situations of Uncertainty (Section 2); and what to do when you are in a Situation of Uncertainty (Section 3).

You'll be pleased to know that this section (Section 4) is NOT about Situations of Uncertainty! It is about teaching students what to do when they are in SITUATIONS OF CONFIDENCE. 

What do we do at crossings in a Situation of Confidence? 

Well, since being in a Situation of Confidence means that we can hear and/or see the traffic well enough to figure out when there is a crossable gap in traffic, we go ahead and cross when there is a crossable gap, of course! 

But wait -- that's assuming that we KNOW how to figure out when there is a crossable gap in traffic! 

And THAT is what this Section is all about -- teaching students how to use their hearing and/or vision to figure out when there's a crossable gap in traffic at Situations of Confidence. 

We will cover each of the following for crossing in Situations of Confidence:Determining when it is "clear to cross"

Using hearing; Using vision (looking from side to side);

Determining when there is a crossable gap in traffic that you can see approaching (knowing it is slow/far enough to allow you time to cross);

Learning to make that determination when looking from side to side;For students who have both functional vision and hearing:

Understand the advantages and disadvantages of each and how to use them; Be able to choose which is best for each situation. 

This sums up all that is covered in this Section. As you read each page, please remember these are strategies only to be used when you are in Situations of Confidence. Enjoy! 

Page 1 of 16

Skills needed to determine when it is "clear to cross" if you are in a Situation of Confidence

Using hearing you need to: know what to listen for and be able to "tune in" to those sounds; be able to determine when it is quiet enough to be "all clear" (understand the effect of masking

sounds)

using vision you need to: know what to look for and how to see it effectively and reliably; be able to determine it is "all clear" by scanning / glancing left/right efficiently 

If you can see traffic at a distance you can determine whether you still have time to cross if you can:  determine if the time-to-arrival of the approaching traffic is long enough to cross and make this determination by glancing / scanning to each side. 

If you have usable vision and hearing, you need to understand: what are the advantages / disadvantages of each, and when to use which. 

Teaching these skills is what this section is all about! 

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USING HEARINGto determine when it is "clear to cross"

Know what to listen for and "tune in" to those sounds 

Students can greatly improve their ability to hear approaching vehicles with experience -- as Daniel Kish says, people develop a knack for it when they listen intently on a regular basis. For example, at my street-crossing workshops I've noticed that those who regularly listen for traffic to cross streets can hear the approaching vehicles much sooner than those who do not. 

Suggestions: Have the student listen for approaching traffic, and record the detection-to-arrival times of the

vehicles that are heard when it is quiet. After listening intently for a while, the times of detection-to-arrival will probably get longer as the student learns to "tune into" the sound of the approaching traffic.

Daniel Kish suggests that turning the head periodically can greatly improve the detection of minute sounds, especially against a noisy background such as wind or other traffic sounds. Perhaps the reason this is effective is because it shifts or refreshes the sound, which attracts the brain's attention to it.

Daniel Kish also suggests stepping back or forward, listening to find the best position to hear the vehicles -- this may also avoid or reduce any blocking of the sound of the vehicles. 

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USING HEARINGto determine when it is "clear to cross"

Be able to determine when it is quiet enough to be "all clear" (understand the effect of masking sounds) 

Is this skill really necessary? 

The importance of understanding the effect of masking sounds hit me like a ton of bricks when I went back to analyze the crossing where Sue Etters was hit. I had assumed that Sue had been crossing in a Situation of Uncertainty because she said she crossed only when it was quiet, and yet she was often surprised by vehicles that she hadn't heard when she started crossing. 

When I was finally able to assess the situation, I was shocked to find that it was NOT a Situation of Uncertainty, even when the road was dry and it was 4:00 in the afternoon (when the sound level of "quiet" is usually highest)! 

So what's going on here? If this was not a Situation of Uncertainty, why was Sue often surprised and eventually hit by a car she hadn't heard when she started crossing? 

Well, to make a long story short, I found out that when Sue thought it was "quiet," there were actually still some masking sounds from receding cars. And I had noticed that her crossing was one of those places   that I told you about, where even the slightest masking sound, such as receding cars after they were out of sight, or a train in the distance, kept me from hearing vehicles with enough warning. 

So Sue didn't realize how quiet it had to be. She hadn't noticed that the sound of the distant cars made her unable to hear the sound of the approaching cars until it was too late. 

That is why it's important for your students to understand the effect of masking sounds and, in situations where they can be confident that "it's clear to cross when quiet," they need to know how quiet it has to be in order for that strategy to be effective! 

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USING HEARINGto determine when it is "clear to cross"

Teaching students to determine when it is "quiet enough," and understand the effect of masking sounds 

Students need to be able to . . . NOTICE masking sounds (sounds that are not part of the ambient residual sound) and EVALUATE THE EFFECT of those masking sounds on their ability to hear approaching vehicles. 

Noticing masking soundsOne strategy that may help is to ask the students to indicate when they think it is "quiet" (or as quiet as it can be in that situation!). If they are reporting that it is "quiet" when there are actually some masking sounds (such as receding vehicles, distant lawnmowers or airplanes, etc.) help them learn to notice those sounds. 

They may not report some sounds because they think the sounds are not loud enough to cause a problem, and they may be right! But you want to be sure they at least NOTICE the presence of those sounds. Learning whether those sounds make a difference is the next step. 

Learning the effect of various masking sounds in different situations on the ability to hear approaching vehicles.

As we've explained in Section 1, a little masking sound usually isn't a problem, but sometimes even the slightest sounds can drastically reduce the ability to hear approaching vehicles. Students can learn about the effects of masking sounds by observation, either formal or informal as described below: 

Informal observations: When students can hear a car coming from a distance, have them notice that they can't hear

cars coming behind it (or sometimes cars coming from the other direction) until after the first car has passed. Make sure they understand that this is because the sound of the first car masked the sound of the second car.

When students are measuring the detection-to-arrival times of approaching vehicles, have them notice how much shorter those times can sometimes be when there is another sound such as an airplane or receding car. 

Formal observation: You can help students learn to judge when masking sounds are loud enough to significantly impact their ability to hear approaching vehicles by creating steady masking sounds and letting them observe what happens: 

Step 1: Find a situation where the student can hear approaching vehicles with enough warning to know that it is clear to cross when quiet. Step 2: Create a steady masking sound (I use a recording of my vacuum cleaner!) and ask the student if he can still hear the vehicles well enough.   Make sure the source of the masking sound (such as the tape recorder) stays in the same place and remains steady throughout this process. 

Step 3: Use the TMAD measurements to assess whether the student was correct about being able to hear the approaching vehicles above the masking sound with enough warning. 

For example, perhaps a student judges that in a certain situation she can hear the vehicles with enough warning to know that it's clear to cross whenever it is quiet, and the TMAD measurements indicate that her assessment was correct. You then can play a recorded steady noise softly and ask the student to judge whether she can still hear the traffic well enough above the noise, while you measure detection-to-arrival time to give her feedback. Sometimes I ask students to set the volume of the recorded noise themselves, making it just low enough that they think they can still hear the vehicles over that masking sound, and then we use the TMAD to see if the masking sound was loud enough to impact the warning time. 

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USING VISION to determine when it is "clear to cross"

Visual tasks for crossing streets 

So far, we've talked about listening for vehicles to identify when it's clear to cross. Now we're going to consider the task of looking for vehicles to determine if there is a gap in traffic long enough to cross. 

Basically, there are two visual tasks for crossing streets IF you are in a Situation of Confidence: 

1. Watch for "all clear:" This task involves looking to make sure nothing is coming. 

2. Determine if gaps in traffic are long enough: Students who can see vehicles approaching in the distance may be able to determine whether those vehicles are far/slow enough to allow time to cross before they arrive. 

Assessment and training of this skill may be just as important as the skill of making sure it's "clear to cross." Lack of this skill may be what caused the deaths of Dick and Lorraine Evensen at the crossing shown in the photo to the left, and research suggests that some people with visual impairments think that their ability to judge gaps in traffic is better than it actually is (Cheong, Geruschat, and Congdon, 2008). 

But WAIT! There's MORE -- and it's critically important! 

Glancing or scanning in each direction: Unlike listening for vehicles, which can be done from both directions at once, people can look for vehicles in only one direction at a time (unless they have two heads like the woman in the photo!). This means that both of the visual street-crossing tasks (watching for "all clear;" and determining if gaps in traffic are long enough) must be done while looking from side to side to make

sure there is a crossable gap in both directions. 

This will all be covered on the next few pages, starting with learning how to look for vehicles effectively. 

Cheong, A.M., Geruschat, D.R., Congdon, N. (2008). "Traffic gap judgment in people with significant peripheral field loss." Optometry and Vision Science, American Academy of Optometry. Vol 85, No 1: pp. 26-36

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USING VISION to determine when it is "clear to cross"

Knowing what to look for, and how to see all vehicles effectively and reliably 

Just as students who use their hearing need to learn how that hearing is affected by conditions such as ambient sound level, blockage and masking of sounds, and clogged ears or head congestion, students who use vision to watch for vehicles need to understand how lighting, sight lines, and features of vehicles can affect their ability to see them. 

For example, they may notice that certain features of vehicles (headlights, sun reflection, certain colors, etc.) make the vehicles easier

or more difficult to see. they can see a vehicle more easily if they see its movement, so that it is easier to see vehicles

approaching at an angle where there is cross-movement than to see vehicles approaching directly toward them.

lighting conditions (sunny, cloudy, night) can affect their ability to see the vehicles. their line of sight may be blocked temporarily by passing vehicles. their vision fluctuates, and they can see better or worse at some times than at others. 

They may also benefit from learning to use their vision more efficiently.  Students with central scotoma (such as macular degeneration) might use eccentric viewing to look

for vehicles with their best point of fixation. Students with sensitivity to light may benefit from sunglasses and visors that shield them from the

sun and glare.

Students with acuity loss might see approaching vehicles sooner by using a telescopic aid effectively.

If using a telescopic aid, they may need more time for their crossing. Using a telescopic aid may reduce their field of vision which could affect their ability to scan

left/right for approaching vehicles, so it is important that they learn to do so efficiently (see the next few pages for suggestions about reduced visual fields). 

As with hearing, there will be Situations of Uncertainty where they cannot reliably see all the vehicles with enough warning to be confident that it's clear to cross whenever they see nothing coming. These situations should be handled as explained in Section 3. 

Once your students have learned to watch for "all clear" as efficiently as possible, they need to learn how to do it by scanning / glancing left/right efficiently. That is covered in the next few pages.

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USING VISION to determine when it is "clear to cross"

Look for vehicles by SCANNING or GLANCING left / right 

Challenges and strategies for scanning / glancing side to side Pedestrians need to look both left and right to be sure it is clear to cross in both directions, but this can be difficult for some people with visual impairments. If they glance or scan incorrectly, they may miss seeing some of the vehicles. The next page has suggestions for training students to scan or glance effectively, but first I'll explain the scanning challenges and suggested strategies for two common visual impairments: 

* Severely restricted visual field, such as with retinitis pigmentosa (RP) (using a telescope may also restrict visual fields) * Central scotoma with loss of visual acuity, such as with macular degeneration 

Severely restricted visual field         CHALLENGE WHEN LOOKING FROM SIDE TO SIDE FOR VEHICLES: 

May miss seeing vehicles that are nearby (especially vehicles in the "blind spot") Try looking for something through a long tube like a paper towel roll. If you move the tube quickly from side to side and back again, you may see what's at your sides each time you stop moving the tube long enough to move it back to the other side, but you can't see anything in between. That is what happens

when people with less than about 5-10 degrees of central vision try to look quickly from left to right and back -- they see what's on the street far to their left and their right, but nothing in between, including vehicles that are near to them. The same thing can sometimes happen when using a telescope, too. 

In addition to the problem with not being able to see details when scanning quickly with a small field of view, vehicles that are close are difficult for people with this visual condition to see. This is because the further that they are from an object, the more of it they can see -- illustrations of this principle are in Considerations of restricted visual fields. 

There are two videos that simulate restricted visual fields. Click here for the first video; it shows that when glancing quickly with about 5 degrees of visual field, you can see the vehicles that are in the distance more easily than you can see those that are near to you. Click here for the second video, which compares glancing with normal vision and glancing with simulated visual field restriction. Both videos then show how much more effective it is to scan slowly. 

BLIND SPOT:Although people with severely restricted visual fields might miss seeing approaching vehicles that are close, it is a problem only when the vehicle is in the nearest lane. Vehicles in further lanes are usually not a problem because if they are approaching closely and are undetected when a person starts her crossing, those vehicles are likely to have passed by the time she reaches their lanes. 

So there is only one place where it is extremely important that they not overlook vehicles -- a place which I call "the blind spot" for people with restricted visual fields. That place is in the nearest lane where the vehicle is so close that if they miss seeing it and they start to cross, the driver might be unable to stop -- yikes! The photo to the right shows a vehicle in the blind spot, about two car-lengths to the left of the person with the cane wearing a vision simulator. (Click here if you want to read the scary story of how I discovered this.) 

SOLUTION: scan slowly. 

The videos above demonstrate that with a restricted visual field, when you scan slowly you can see vehicles that you missed when you scanned more quickly. Students need to learn how slowly they must scan to ensure that they don't miss seeing any vehicles in the "blind spot," as explained on the next page. 

SUMMARY:The most difficult vehicles for people with restricted visual fields to see are 

in the nearest lane, about two car lengths to their left (in the "blind spot" as shown in the photo above). 

The strategy to help see the vehicles better: scan slowly.

  Central scotoma with loss of visual acuity:         CHALLENGE WHEN LOOKING FROM SIDE TO SIDE FOR VEHICLES: 

May miss seeing vehicles in the distance . Students with macular degeneration and other central scotomas have a loss of acuity, which can make it difficult to see details such as objects that are small or far away, as demonstrated in the video to the right below. There are two strategies that can help them be more likely to see vehicles approaching from a distance: eccentric viewing, and holding their glance long enough to notice if there is any movement. 

ECCENTRIC VIEWING:With training, people with central scotoma can learn to find and use the best part of their peripheral vision, which is called eccentric viewing. This training should be done before they learn to analyze and cross streets -- the skill can then be used to look for vehicles.

HOLDING THE GLANCE LONG ENOUGH TO SEE MOVEMENT:Even with skillful use of eccentric viewing, the peripheral vision has poor acuity. However, the peripheral vision excels at detecting movement. That means that people with central vision loss may not be able to see vehicles that are parked in the distance, but they can detect them if they are moving. 

So when these students look for vehicles, they need to hold their gaze long enough to notice if there is any movement, as illustrated in the video. 

SUMMARY: The most difficult vehicles for people with central scotomas to see are approaching from a distance 

(as shown in the photo to the right). 

The strategy to help see the vehicles better: hold the glance long enough to

notice if there is any movement.

The next page has suggestions for training people to scan or glance effectively. 

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USING VISION 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.

Materials needed: An appropriate street to practice (see below). Something to occlude the hearing (earplugs and sound-blocking headphones, and/or a steady

masking sound such as a recording of traffic or a vacuum cleaner)

1. Have the students practice watching for vehicles in one direction (see "USING VISION to determine when it is "clear to cross" ).

2. When they are experienced with looking for vehicles in that direction and are ready to try doing it while glancing or scanning, discuss with them any challenges they may have with this task and possible strategies.

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:

o 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").

o 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 WITH A RESTRICTED VISUAL FIELD

The first example is a video (click here for the 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, (click here for the video), 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!

Page 9 of 16

USING VISION to determine there is a crossable gap in approaching traffic

We had been talking about crossing in Situations of Confidence whenever you know it's "clear to cross" because you hear/(see) nothing coming.

** Now we're going to talk about crossing in situations where you can see traffic approaching from a distance.

You might be asking yourself "How on earth would our students with visual

impairments ever be able to see traffic in the distance?

And why the heck would anyone cross when they know that vehicles are approaching?"

I'll answer the first question first. Many people with visual impairments such as retinitis pigmentosa and macular degeneration can see traffic quite far away. In these situations, they may want to cross when they determine that the traffic is far and/or slow enough that they can cross -- that is, when the "time-to-arrival" of all the approaching vehicles provides enough time to cross.

For example, Lorraine Evensen had albinism and undoubtedly could see the headlights of approaching cars more than 2 blocks away at the crossing (shown to the right) where she and her husband Dick were killed. However, she apparently misjudged how close and fast those cars were. We want to make sure that our students do not make the same mistake, and think there is time to cross when there actually isn't.

Now the second question -- why would anyone cross when they know that vehicles are approaching? The answer is that this is how most people cross. If they didn't, they would be very limited because there are many situations where there are always approaching vehicles visible in the distance, providing no "all clear" opportunities for crossing.

So most people are very familiar with the task of judging whether the approaching vehicles are far/slow enough to allow them time to cross. In fact, the accuracy of this judgment is something that has been studied for many years. It's a skill that is necessary for travel in many areas; pedestrians and drivers who want to cross busy streets will watch the approaching traffic until they think there is a gap long enough to cross. They don't do it by counting seconds or using a stopwatch, they've learned to do it naturally and instinctually, and their lives often depend on how well they can do it.

Many of our students can learn to do it accurately, and they should be able to do it naturally and instinctually. I'll share a story with you about developing what I call the "WHOA!" feeling:

When doing research with Gene Bourquin and Rob Wall Emerson, my job was to watch the approaching vehicles and tell Gene the moment that they were 5 seconds away, so that he could start walking into their path (yes, that does sound crazy, doesn't it? But we learned a LOT when drivers thought they would hit him if they didn't stop!).

Anyway, I took about 5 minutes to train myself to make this judgment accurately, and we started. At first I made the judgment by consciously projecting the path of the vehicle and imagining Gene walking forward to determine when he should start so that they would be on a collision path. But after about half an hour, I didn't have to consciously do anything! All I had to do was watch those vehicles approaching until I got this physical "WHOA!" feeling in my gut, a feeling that said "It's too late, if I start to cross now and the vehicle doesn't slow down, it could hit me!" That "WHOA!" feeling turned out to be as accurate as my conscious visioning and projecting had been.

This gut feeling of "WHOA! It's too late to start crossing!" can be the goal of this training for our students. To summarize, the skills that our students need in order to know the approaching traffic is far and/or slow enough to allow them time to cross are:

Be able to naturally and instinctually determine if the time-to-arrival of the approaching traffic will be long enough to cross; and

if crossing a two-way street, be able to make this determination by glancing / scanning.

And THAT is what the next few pages will cover!

Can people make this judgment by using their hearing?

Well, yes and no -- primarily NO!

Research has shown that people can learn to determine from the sound of an approaching vehicle how much time will pass before it arrives, BUT using this skill may be UNRELIABLE for determining if you have enough time to cross!

The reason it is unreliable is that the sounds of one approaching vehicle can mask the sound of other vehicles. So even though people can determine that the vehicle they hear will not arrive before they finish crossing, the sound of that vehicle may mask the sound of other vehicles that will arrive sooner.

I therefore believe that even though students should be taught to use their hearing to reliably determine when it is clear to cross ("cross when quiet") in Situations of Confidence, it is inadvisable to train students to use their hearing to judge whether they have enough time to cross when they can hear that vehicles are approaching.

For these reasons, the following pages will focus only on teaching people who can use their vision to determine whether there is still time to cross when they can see that vehicles are approaching.

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USING VISION to determine there is a crossable gap in approaching traffic

Procedure to teach students to judge if there is a crossable gap

After enough practice with feedback, students who have sufficient vision and can see vehicles approaching in the distance can usually learn to judge whether or not they have time to cross before the approaching vehicles arrive (that is, judge whether the vehicles are far and/or slow enough that there is time to cross).

Below is the procedure I use to provide this practice and feedback. I call the procedure "Determining Gaps in Approaching Traffic" (I used to call it the "Timing Method for Assessing the Speed and Distance of Vehicles" but too many people confused it with the TMAD).

Prerequisite?

Students seem to learn this skill much faster if they have developed an intuitive understanding of their crossing time before the training. It usually takes only a few minutes to help students develop this intuitive understanding, so the time invested in this is worthwhile.

Determining Gaps in Approaching Traffic(was "TMASD")

Procedure:

1. Determine how much time the student needs in order to cross with enough clearance or safety margin, and add a one-second "fudge factor" (this is explained in more detail on the next page). We will call this time "X."

2. Have the students stand at the curb and, as a vehicle approaches, start a stopwatch when they think it's the last possible moment that they could start a crossing with enough time to get out of the path of the vehicle with a safety margin.

3. Stop the watch when the vehicle reaches the students, and report to the students how accurate they were.

If the lapsed time is within a second of "X," it would be considered acceptable. For example, if "X" is 9 seconds and the student started the stopwatch when the vehicle was between 8 and 10 seconds away, that would be considered acceptable.

If the lapsed time is significantly longer or shorter than X seconds, the students can use this feedback to modify when they think there is still time to start crossing.

Some instructors are tempted to consider anything longer than "X" as being acceptable, but if your goal is to help the students develop good judgment of the speed and distance of the vehicles (get that “whoa!” feeling in their gut when it’s too late to cross), then they need to know that they were incorrect if they started the stopwatch when the vehicle was significantly longer than "X" seconds away.

4. Students continue to judge the approaching vehicles as in steps 2-3, with the goal of improving their judgment until they can discern when the vehicles, regardless of their speed, still allow the students time to cross with their safety margin. As students become skilled, they will start the stopwatch for faster vehicles when they are further than they will for slower vehicles.

NOTE: If a vehicle changes speed while being timed, disregard that trial, since in that situation it isn't possible to know whether the student accurately judged its speed and distance as it approached.

IMPORTANT!:Students who use vision to cross should learn to make this judgment in a variety of lighting conditions, including at night. It may be that they can do it well in certain lighting conditions and not others, and they need to know that. For example, it was at night that Lorraine Evensen misjudged how close and fast the traffic was coming -- if she had realized her judgment was not good, would she have chosen other strategies for getting across the street?

CAUTION ABOUT USING LANDMARKS TO JUDGE GAPS:

Students will NOT develop and improve their judgment of the speed and distance of vehicles if they use a landmark along the street to help determine when the approaching vehicles are "X" seconds away.

Adriana Hermosillo, an O&M specialist who trained people to judge gaps as part of a research project, explains the problem as she experienced it. When she started learning to judge gaps in traffic, she noticed there was a prominent landmark -- a dip in the road where the median strip and lane markings ended, as shown in the photo to the left (a car is passing that landmark). She said:

When I first attempted this exercise I was looking at where the cars were in relation to various landmarks to determine when they were "X" seconds away. The dip in the road was significant enough to draw my attention. With the feedback I received, I realized that if we started the stopwatch just as the car approached the dip, my timing was perfect. All I was doing was using that landmark, not taking into account the actual vehicle or its speed.

I didn't even realize I wasn't learning the skill of judging gaps until we moved to a place that had no prominent landmark, and then I was clueless about judging the vehicle's speed or distance. That is when I actually practiced the skill of judging gaps based on the car's speed and distance -- I isolated my attention solely on the car, which is critical to gain the ability to judge gaps in traffic."

Doesn't seem to be working?

If the students' judgment does not begin to improve after about 10 minutes, it may be because they are unconsciously using a landmark, as Adriana was – try doing the training somewhere that doesn’t have the natural landmarks.

If the students’ judgment still does not improve, perhaps they are unable to perceive the speed and distance of vehicles accurately, at least in that situation, either because of visual limitations or the student is unable to cognitively process it. When this happens, the student could consider an alternative for determining when there is a crossable gap in approaching traffic.

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USING VISION to determine there is a crossable gap in approaching traffic

In the last page, you learned that Determining Gaps in Approaching Traffic requires that you define a length of time, which we will call "X" seconds. This page has more information about how to determine how many seconds is "X" seconds.

How to determine how many seconds is "X" seconds?

"X seconds" is typically: the time needed to cross, plus a preferred safety margin ("clearance time"), plus an extra second to allow for error.

o The time needed to cross is the time it takes to get across the street or lanes and be safely out of the path of traffic. For two-way streets in countries where vehicles travel on the right side of the street, the first lanes that you cross have traffic from your left. Therefore your crossing time for traffic from your left would be the time needed to cross the first part of the street (all the lanes with traffic from your left), and crossing time for traffic from your right would mean the time needed to cross the entire street.

o The preferred safety margin / clearance time) is the preferred minimum time from when you complete the crossing until the first vehicle passes your crosswalk.

Most people think it's cutting it too close if they finish their crossing just as the traffic reaches them - yikes! So they prefer additional time for a safety margin, which is why we add this to their crossing time. How many seconds are needed for the safety margin may vary -- people usually want more clearance time for fast-moving traffic than they do for slow traffic, and cautious people may want a longer clearance time than high risk-takers do.

One way to find out how much safety margin a person needs is to use a stopwatch and say something like,

"We need to figure out how much time you need for your safety margin for this crossing. To help you decide, I'll demonstrate a two-second safety margin. I want you to imagine that you're crossing the street and you know a vehicle is coming but you're feeling comfortable with the clearance that you have. So imagine that you finish the crossing and step onto the curb NOW" . . . [wait two seconds and then say] "NOW is when that vehicle would reach you. Does that safety margin seem to be enough time for you?"

If that doesn't seem long enough, demonstrate a 3-second safety margin and ask if that is enough and if not, demonstrate a 4-second safety margin and ask again. Be prepared to change the length of the safety margin during the training because sometimes people change their minds as they practice with real traffic, deciding that they need either more or less time for their safety margin.

o The one-second error margin or "fudge factor" is needed because most people can learn to make this judgment accurately within one second or less. That is, they can determine when the vehicle is X seconds away, give or take a second. I am concerned about the possibility that when they apply this skill in real situations, they will misjudge it by a second less than they need, so I like to add a second to take this margin of error into consideration.

The crossing time, the preferred safety margin, and the error margin should all be considered when determining how many seconds "X" will be. For example, if you need 6 seconds to cross and want a safety margin / clearance time of 3 seconds, you want to be sure the traffic is at least 9 seconds away when you start to cross. Thus your "X" should be 10 seconds, so that if you misjudge the arrival time by one second less than it actually was, you'd still have the full 9-second gap that you want.

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USING VISION to determine there is a crossable gap in approaching traffic

ALTERNATIVE when you cannot judge whether the traffic is far/slow enough to allow you time to cross:

I have had about a half-dozen students who were able to see the vehicles at a distance but were unable to judge their speed and distance. There is an alternative that they were each able to use for judging whether they have enough time to cross when they see vehicles approaching.

This alternative is to choose a landmark (such as a driveway, or pole, or tree) at a distance such that, from that spot, even the fastest vehicles take more time to reach them than they need to cross. The TMAD can be used to help determine if the landmark is far enough. If it is, then you can be confident there is enough time to cross if there are no vehicles closer to you than that landmark.

Note: This is an alternative strategy for those who are not able to judge the speed and distance of the vehicles. While students are still trying to learn to judge the speed and distance of the vehicles, do not suggest that they start the timer whenever the vehicle passes a certain landmark, as this will impede their learning to judge the gaps in traffic.

Note: In my experience, people who do not have binocular vision (for example, have only one functioning eye) have done very well with judging the speed and distance of the vehicles. Those who cannot do it are more likely to be people with very small visual fields than people with monocular vision. Perhaps this is because, for judging speed and distance of an approaching vehicle, even more

important than binocular vision is the ability to see what is around that vehicle, such as the trees, bushes, and poles that it is passing.

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USING VISION to determine there is a crossable gap in approaching traffic

Determine when the traffic is far/slow enough by SCANNING or GLANCING left/right

As we've said before, people who use vision to cross a street need to assess the situation by looking at the traffic approaching from several directions, one at a time.

Thus, after they have practiced to become proficient with Determining Gaps in Approaching Traffic in one direction, students should learn to make that judgment accurately when scanning or glancing in that direction. For issues that must be considered for scanning and glancing with various eye conditions, see page 7 in this section.

Procedure to train students to determine if there is a crossable gap in traffic while scanning / glancing to each side

For this training, do NOT occlude the student's hearingYou may remember that when you are training students to scan or glance to detect the presence of vehicles, you occlude the students' hearing to make sure they can detect the vehicles even when there is too much noise to hear them.

But now you are training students to scan or glance to determine if the approaching vehicles are far/slow enough to allow you time to cross. Research shows that judging the speed and distance of approaching vehicles involves hearing as well as vision, and you want the students to learn to make this judgment in realistic conditions, so do NOT occlude the students' hearing for this training.

Procedure:Once the students have learned to judge when the traffic in one direction is far/slow enough to allow them time to cross (as described on page 10), have them practice doing it by glancing as follows:

Have the students face the street. Prepare the students by telling them that you will ask them to turn and glance at the

approaching traffic in one direction and determine whether they would have time to cross. They can report to you that either there is enough time to cross, or there is not, or that it is too close to call.

Tell them that for this exercise, they should look at the traffic just long enough to make that determination, then look forward again and report their judgment.

Once the students are ready, wait until there is a vehicle or traffic approaching that you want them to judge. I like to start out with situations that are obvious and easy to judge and, after they do well with those, I choose situations that are more difficult, so the first few situations have approaching vehicles that are either much too close/fast or still plenty far/slow enough to allow the student time to cross.

When the approaching vehicle or traffic is where you want it to be, tell the student to turn and look.

As soon as the student finishes glancing at the traffic and starts turning to face forward again, start a stopwatch, and ask the student if there would have been enough time to cross. When the first vehicle passes the crosswalk, stop the watch and tell the student whether or not s/he was correct.

If the student reported that there would have been enough time to cross, s/he would have been correct if the time

to arrival was at least "X" seconds, and incorrect if it was less. there wasn't time to cross, s/he would have been correct if the time for the vehicle to

arrive was less than "X" seconds, and vice versa. it was too close to call, s/he would have been correct if the vehicle was "X" seconds

away (give or take a second).

For example, suppose the student's "X" is 6 seconds. You ask the student to turn and look, and when the student has finished looking and is turning back to face straight ahead, you start the timer. Meanwhile, the student reports that there would have been enough time to cross. When the vehicle arrives, the stopwatch indicates it was 10 seconds away when the student was finished looking. You report to the student that s/he was correct; there was enough time to cross when s/he had made the judgment.

You may be asking, "Why start the timer when the student has finished looking and is turning to face forward again?" It's because when the students are assessing situations and plan to cross, they need to make sure they still have time to cross after they have made that determination, not when they first turned to look.

If the students judged incorrectly (for example they thought it was too late to start a crossing but the stopwatch said there was plenty of time), they learn from the feedback and try to improve the glancing next time. Usually what they needed was more time to view the approaching vehicles before making their determination, but sometimes the problem is that they hadn't had enough practice Determining Gaps in Approaching Traffic.

Continue until the student has demonstrated accuracy with glancing / scanning to assess whether there is time to cross.

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Using HEARING or VISION -- Which is better to Determine when it is "clear to cross"?

WHEW! You've made it through the pages that describe how to teach students to determine that they have enough time to cross, either by crossing when it's "all clear" or by crossing even though they can see something approaching in the distance because they know they still have time to cross before it arrives. Congratulations!

Hang on, we're almost finished, we just need to talk about students who have both functional hearing and vision. They need to realize that

the process of using hearing to cross streets is vastly different from the process of using vision, and each has its advantages and disadvantages.

HEARING Process for detecting approaching vehicles using hearing:

Wait for quiet to detect the vehicles. Advantages:

can detect vehicles approaching in all directions at the same time; can often detect vehicles approaching from beyond hills and bends in the road and other

obstacles (though the sound may be reduced).Disadvantages:

can not detect vehicles if there are masking sounds such as other vehicles receding, wind, etc.

Photo to the right shows a situation where hearing is much more effective than vision. The approaching vehicles cannot be seen until they are 4-7 seconds away but they can be heard 7-18 seconds away (if you want to see the detection times, click here).

VISION Process for detecting approaching vehicles using vision:

Look in one direction until clear and then the other and back again, using whatever strategy is necessary to effectively glance or scan from one side to the other to be sure there is a crossable gap in both directions.

Advantages: can detect approaching vehicles even with loud noises and other vehicles nearby.

Disadvantages: cannot detect vehicles approaching from beyond hills and bends in the road and other

obstacles (including other vehicles); cannot detect vehicles in both directions at once -- while looking in one direction, vehicles

may approach undetected from the other direction.

Photo to the right shows a situation where vision is more effective than hearing. The approaching vehicles can be seen more than a block away but even when it is quiet, they cannot be heard until they get near the bottom of the hill.

Students may overestimate or underestimate the benefits of using vision or hearing because they don't know how to use them and don't understand their limitations. Thus it is very important that they

learn how to use each effectively for crossing streets; understand the advantages and limitations of each so they can recognize which would be best for a

given situation; and recognize situations when neither their hearing nor their vision, even when used as effectively as

possible, can detect the traffic well enough to know when it's clear to cross (Situations of Uncertainty).

Because vision and hearing use very different processes, it is usually difficult to look for approaching vehicles in both directions as efficiently as possible while at the same time tuning into the sound of approaching vehicles and listening for them as efficiently as possible, and vice versa. Travelers therefore usually need to decide in each crossing situation whether it would be best to maximize the use of their hearing or their vision to detect the vehicles. These issues will be discussed on the next page.

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Using HEARING or VISION -- Which is better to Determine when it is "clear to cross"?

Teaching students to choose vision or hearing to detect vehicles

We've already talked about teaching students to use their hearing and teaching them to use their vision to detect vehicles. For students who have both vision and hearing it can be helpful for them to learn to use their hearing for crossing streets separately from learning to use their vision, and vice versa (for an example, you can read Vignette 4 -- Using vision and hearing).

After students know how to use their vision and how to use their hearing effectively, you can give them experience at a variety of crossing situations. At each situation, you can ask them to determine whether it is a Situation of Uncertainty and if not, whether they can reliably detect all the approaching vehicles in that situation better with vision or with hearing.

Once they make their judgment, assess the situation with the TMAD twice (once while using their vision and once while using their hearing) and give them feedback as to whether they judged correctly.

You could assess both hearing and vision at the same time with the TMAD by documenting when they first hear AND when they first see each vehicle coming, if it is quiet when they first hear it. But students may be able to see a vehicle sooner if they hear it first, and may be able to hear a vehicle sooner if they see it first, so if the purpose is to assess hearing only, the student's vision should be occluded and to assess vision only, the hearing should be occluded with noise blockers and/or earplugs.

Make sure the students have experience in situations in which they can see the traffic better than they can hear it, situations in which they can hear the traffic better than they can see it, and Situations of Uncertainty in which neither their vision nor their hearing is good enough.

The Checklist Using Vision & Hearing may be helpful to document the experiences of the student.

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Review:

Congratulations, you've finished Section 4! This section covered skills for crossing when we are in a Situation of CONFIDENCE and we can determine when there is a crossable gap:

USING HEARING -- knowing what sounds to listen for, and recognizing when it's quiet enough; USING VISION to determine it's clear to cross –

o being able to look in both directions o challenges and strategies for looking in both directions effectively;

being able to determine when the traffic is far/slow enough to allow you time to cross; Noting that although it's possible to make this judgment for single vehicles by

hearing, it is not advisable to do so because the sound of that vehicle can keep you from hearing other vehicles;

o Determining Gaps in Approaching Traffic ; o being able to judge when traffic is far/slow enough while glancing;

considering whether to LOOK or LISTEN for the traffic.

Which procedure do you use when? In Section 2 you learned about the Procedure to Develop Judgment of the Detection of Traffic which uses the TMAD to give students feedback to help them learn to recognize Situations of Uncertainty, and now you've learned about Determining Gaps in Approaching Traffic.

Some people are confused about which procedure should be used when, so this summary may be helpful. Timing Method for Assessing the Detection of Vehicles (TMAD) :

The key word in the name TMAD is DETECTION. The TMAD is used to assess the DETECTION of vehicles to find out if you have enough warning of their approach. When would you want to assess someone's detection of vehicles? You want to do that when you

o teach students to recognize when they can not DETECT vehicles with enough warning (that is, teach them to recognize Situations of Uncertainty);

o help students understand the effect of masking sounds on their ability to hear (DETECT!) approaching vehicles.

Determining Gaps in Approaching Traffic helps train students for situations when they can see the vehicles in the distance. So, you are not worried about whether they can detect the vehicles with enough warning, they can see them plenty far away. You're worried about whether they realize the vehicles are too close/fast to start their crossing.

Why would you have them practice Determining Gaps in Approaching Traffic? Because it helps your students learn to:

o recognize when they have enough time to cross even though they can hear or see vehicles approaching in the distance (that is, recognize when the traffic is far/slow enough to allow them time to cross). For example, we know that when Lorraine Evensen and her husband Dick were killed, she could see the vehicle that killed them approach from a distance. If she had practiced Determining Gaps in Approaching Traffic, she probably would have realized that the vehicle was too close / fast to allow them time to cross (or she would have realized that at night, she is not able to make that determination).

Whew! Well, now you are ready to start the last section, which might be the most fun. You've already covered all the essential information -- Section 5 has scenarios, frequently asked questions, and outside activities, all of which can help you process and apply what you've learned. Enjoy!