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Section 1: Introduction to Situations of Uncertainty Table of Contents (Page links take you to the website pages)

Section 1: Introduction to Situations of Uncertainty Page 2: How can we cross at streets and lanes with no stop sign or traffic signal? Page 3: Crossable Gaps Page 4: Dedicated to the memory of Dick and Lorraine Evensen . . . The history of realization Page 5: Using distance vision: Vehicles too fast/Close? Using hearing: "Clear to cross when quiet?" Page 6: Clear to cross when quiet? - 60 years ago and now Page 7: "Situations of Uncertainty" -- Yikes! Page 8: "Situations of Uncertainty" / "Situations of Confidence" -- What are they? Page 9: Research -- are there really Situations of Uncertainty? Page 10: Research -- What did we learn from sitting in lawnchairs? Page 11: So how can we recognize Situations of Uncertainty? Page 12: Uncertainty Prediction Challenge Page 13: So how can we recognize Situations of Uncertainty? Page 14: But aren't there strategies that can assure enough time for crossing these streets? Page 15: Study Questions Page 16: What is "Quiet"? -- Varies between and within communities Page 17: What is "Quiet"? -- Effect of changes in ambient sound Page 18: What is "Quiet"? -- Effect of slight increase of ambient sound Page 19: Situations of Uncertainty . . . does it really matter? Page 20: Another Tragedy -- Can We Learn any Lessons? Page 21: Commitment to Prepare Students / O&M Best Practice Page 22: 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 1: Introduction to Situations of Uncertainty for Gap Judgment

Welcome! This Section explains all about Situations of Uncertainty for gap judgment at crossings that have no stop sign or traffic signal. It defines what we're talking about, covers a little of the history of how we realized that Situations of Uncertainty exist, and explains how to recognize them.

Vision or Hearing?? The concepts and skills needed to recognize Situations of Uncertainty for gap judgment are just as important for people who use vision to cross streets as it is for those who use hearing, and many of the principles are the same for both. However using sounds for crossing can be more complex than using vision, and includes issues that you may not have considered (heck, we even need to talk about what "quiet" really means!).

For that reason, Section 1 focuses more on issues of using hearing than it does with using vision. But keep in mind that the principles for recognizing and dealing with Situations of Uncertainty are the same regardless of whether you are looking or listening for vehicles. Starting with Section 2, the Self-Study Guide deals with teaching these concepts and skills to students who use vision as well as those who use hearing to detect the vehicles.

So . . . let's get started! We'll begin by explaining some terms.

What does it mean to have a crossing with no stop sign or traffic signal?

This Self-Study Guide is about crossings with no stop sign or traffic signal. Other terms are "crossings with no traffic control" or "uncontrolled crossings."

These crossings can be found everywhere -- downtown, suburban and rural areas. Most of them are found at intersections that DO have stop signs or traffic signals, but those signals or stop signs are not for every crossing at that intersection. It's those crossings that we're talking about -- crossings that have vehicles passing through without being controlled by any stop sign or traffic signal.

Examples of these crossings are shown in the photos here:

Right: There are no stop signs or traffic signals within a block of this crossing in suburban Washington, DC. Below: These intersections each have a stop sign for the street beside the pedestrians, but not for the street that they are facing to cross. Thus, even though the pedestrians are all at intersections that have traffic control, they are facing uncontrolled crossings.

 Left below: At roundabouts, there are no stop signs or traffic signals for traffic approaching the crosswalks.

 Right below: This woman is crossing a channelized right-turning lane at an intersection that has a traffic signal for the vehicles on the other side of the island behind her, but there is no signal or stop sign for the lane she is crossing.

In every photo, there is no stop sign or traffic signal for the lane or street being crossed -- that is, the crossings have "no traffic control." Crossings with no traffic control are what the entire Self-Study Guide is about. Page 2 of 22

How can we cross at streets and lanes with no stop sign or traffic signal?

Whether you are using vision or hearing (or both), there are only 3 ways you can cross streets with no traffic control:

You can cross:  during a "crossable gap in traffic" (explained on the next page);  when vehicles in all lanes approaching the crossing have stopped (yielded) for you;  trusting that all drivers who might be approaching will yield for you.

The primary focus of this Self-Study Guide is crossable gaps in traffic, especially:  figuring out when there is a crossable gap in traffic, and  recognizing Situations of Uncertainty where it is not possible to figure out when there is a crossable gap in traffic. The other ways to cross (crossing when drivers have yielded or are expected to yield) can be considered as alternatives for situations where it is not possible to cross during a crossable gap in traffic (or not possible to be sure you are crossing during a crossable gap). Page 3 of 22

Crossable Gaps

What is a gap in traffic?

A gap in traffic is the space and time between vehicles, OR the space and time between YOU (e.g. as a pedestrian) and an approaching vehicle.

Short gaps in traffic: The gaps between vehicles in the first photo are very short -- there is only a second or two between the time that one vehicle passes a point and the next vehicle arrives. If you were standing at the crosswalk, the gap in traffic between you and the next approaching vehicle is extremely short -- yikes!

Long gaps in traffic The gaps between vehicles in the second photo are very long. Hey, we can't even see the next vehicle, so we know it will be a while before it arrives -- that is a long gap in traffic! If you were standing at the crosswalk, the gap in traffic between you and the next approaching vehicles is much longer than the gap in traffic at the other crosswalk.

What are "crossable gaps" in traffic? The definition of "crossable gaps in traffic" is that they are at least long enough to allow time to complete a crossing.

For example, if it takes you 7 seconds to cross a street and the nearest approaching vehicle is at least 7 seconds away, you have a crossable gap in traffic.

Whether a gap is crossable would depend of course on the pedestrian's crossing time -- crossable gaps in traffic can be shorter for pedestrians who can cross in a shorter time than they are for pedestrians who need more time to cross (for example for slower pedestrians or wider crossings). The O&M specialist is responsible to teach students to determine whether the gaps in traffic are crossable. This will be addressed in later sections of the Self-Study Guide. Page 4 of 22 Dedicated to the memory of Dick and Lorraine Evensen, whose deaths in 1987 alerted us to the insidious changes at streets with no traffic control. May their memory inspire and remind us to prepare our students to assess and cross these streets safely.

The history of realization Our journey to understanding these street crossings started on a cold, clear Monday night, January 12, 1987, when Dick and Lorraine Evensen and Dick's guide dog were all killed in a suburb of Washington, DC, crossing the street shown in the picture to the right (you can click here if you want to know more about what happened).

Dick was totally blind and sometimes crossed there alone. Lorraine had albinism and probably could see headlights approaching from quite a distance. Needless to say, those of us who knew Dick and Lorraine were all horrified and deeply grieved.

I dealt with it by obsessing about how it could have happened. I was shocked at what I discovered at that crossing, and the implications for the way we teach people to cross streets when they use hearing to cross (as Dick did) and when they can see or hear traffic from a distance (as Lorraine did).

Bear with me, and I will explain it in the next few pages.

Using distant vision to cross -- vehicles approaching too fast? Too close? I assume that when Lorraine started to cross, she could see the headlights of the approaching cars from a great distance, but did not realize how very fast and very close they were. A few days later when I tried it myself with normal vision in broad daylight, I also greatly underestimated how close and how fast those cars were coming -- yikes!

So over the next few weeks, I came up with strategies to train people to determine when they still have time to cross, so they won't misjudge it the way that Lorraine and I did. I'll explain those strategies later in this Self-Study Guide (Section 4). Using hearing to cross -- "clear to cross when quiet"? Meanwhile, let's consider the situation of Dick, who sometimes crossed this street alone with his guide dog. Being totally blind, he probably used the traditional strategy -- "assume it is clear to cross when quiet."

Blind travelers who rely on hearing had been using this strategy to cross streets successfully for many years. The next few pages, I'll talk about that traditional strategy, and explain what I found out when I analyzed the situation where Dick was killed.

The rest of this Section will follow up on that revelation and explain what we now know about using hearing to cross streets, based on research and experience. Although this Section does not address using vision to cross streets, the use of vision will be addressed in each of the subsequent Sections of the Self- Study Guide.

Sixty years ago, we could always "assume it is clear to cross when quiet." You're probably wondering how I know this is true. I know because Stanley Suterko himself told me! He was one of the first 5 O&M specialists in our profession, and he shared the following story about O&M instruction the 1940's: He told me that whenever any of the blinded soldiers said they were afraid to cross streets, the instructors would demonstrate that it was always clear to cross whenever it was quiet. They did this by having the soldiers listen when it was quiet, and when they heard a vehicle they compared the time it took for that vehicle to reach them with the time they needed to cross. The time from detection to arrival of the vehicles was always more than the time they needed to cross. I asked if there were any exceptions and he said no. Regardless of whether the street was in the suburbs or downtown, they could hear all the cars well enough that whenever it was quiet, they knew it was clear to cross (if there was a car coming that could reach them during their crossing, they would have heard it!).

Is it still always clear to cross when quiet? Since Dick crossed the 6-lane highway himself with his guide dog (according to neighbors), I decided to analyze whether it was clear to cross whenever it is quiet there. I waited till it was quiet, then started a timer when I heard a car coming. It took 10 seconds for that car to reach me so I thought, "Great! If I can hear all the cars at least 10 seconds away, then whenever it is quiet and I don't hear any cars, I know it is clear to cross."

However, I did this again a half-dozen times, waiting until it was quiet and then starting a timer when I heard a car coming.

There were two cars that I couldn't hear until they were only 3 seconds away (one was going very fast, one was cruising very slowly). If I had started to cross just before I heard them (when it was still quiet), they would have reached me just after I entered the second lane.

I was dumfounded. Blown away. The strategy that I had been teaching for 18 years -- "it is clear to cross when quiet" -- was not true at the crossing where Dick and Lorraine were killed.

"Situations of Uncertainty" -- Yikes!

I told our local O&M group, WOMA (the Metropolitan Washington O&M Association), about my horrifying discovery -- at the 6-lane surburban street where Dick and Lorraine were killed, it wasn't possible to hear the cars with enough warning to know if it is clear to cross, even when it was quiet (what we now call a Situation of Uncertainty).

A few weeks later one of the WOMA members, Linda Sussman, called to tell me that she found another place where it was not possible to hear the cars with enough warning to know if it is clear to cross. I bought a videocamera and went to meet her and her client at the crossing.

When I arrived, I thought I had wasted my time because it didn't seem dangerous. It was not another 6-lane throughway, it was a two-lane, residential street with a speed limit of 25 mph and so quiet I could hear nothing but the birds singing.

But then I observed what happens there, as you can see in the video (Click here to see the video). The crossing time is 7 seconds, and some of the cars could not be heard (or seen!) until they appeared around the bend to the right, only 4 seconds away!

It was another Situation of Uncertainty. YIKES! Once again, I was shocked . . .

. . . so -- these Situations of Uncertainty happen not only at wide, speeding throughways. They also happen at narrow, quiet residential streets!

On the next page, we'll consider what Situations of Uncertainty are. Page 8 of 22

Situations of Uncertainty for gap judgment -- What exactly are they?

Situations of Uncertainty for gap judgment (or simply "Situations of Uncertainty") are situations at uncontrolled crossings where you do not have enough warning about approaching vehicles to know whether or not it's clear to cross, even when it's as quiet as it can be in that situation.

It's very simple, really -- that's all there is to it: Situations of Uncertainty are situations where you cannot hear / see the vehicles with enough warning to know whether something is coming that could reach you during your crossing, even when conditions in that situation are optimal!

All people find themselves in Situations of Uncertainty sometimes, whether they use vision or hearing, and whether they are walking or driving across the street. Sometimes a crossing is a Situation of Uncertainty for hearing but not for vision or vice versa, and sometimes a crossing is a Situation of Uncertainty for both hearing and vision, and sometimes it is not a Situation of Uncertainty for either.

Examples of what happens at Situations of Uncertainty are:

 pedestrians using hearing may know that there is a gap in traffic whenever it gets quiet, but they don't know if that gap will be long enough to allow them time to cross. There could be a vehicle that is close enough to be able to reach them during their crossing, but not close enoug for them to be able to hear, even though it is as quiet as possible for that situation.  pedestrians and drivers using vision, because of something blocking their view, or something like fog, or glare, or impaired vision, are unable to see far enough to have sufficient warning about the approaching vehicles.

In all of these cases, if they start to cross when it's quiet and they hear or see nothing coming, there could be a car coming just beyond their ability to detect it -- a car which would have to slow down to avoid hitting them. Situations of Confidence – We CAN still be confident it is "clear to cross when quiet" in many situations today!

Situations of Confidence are situations at uncontrolled crossings in which you DO have enough warning about approaching vehicles so that you can be confident about whether or not it's clear to cross.

People who use hearing to cross are in Situations of Confidence whenever they can hear all the traffic with enough warning when it's quiet (or as quiet it gets in that situation) that they can be confident that if any vehicles are coming that could reach them during their crossing, they'd be able to hear them.

Huh??? Yeah, I know what you're thinking! You had assumed that there are no longer any Situations of Confidence today for people who rely on hearing to cross, especially with the presence of quiet cars.

But that is not true, according to my experience and our research. We studied people's ability to hear approaching vehicles from both directions at 3 different crossings, including the one pictured here, which we called the "Straight" crossing (for obvious reasons!). This crossing was a Situation of Confidence for all our subjects at the time that they were there.

The subjects listened for 144 vehicles approaching from both directions at the "Straight" crossing when it was quiet, and they heard ALL the vehicles with enough warning to know that whenever it is quiet, they can be confident that it's clear to cross. If you want to read the data, Table 1 of our report shows that all vehicles were heard at least 7 seconds away, and since the crossing time for the average pedestrians is 7 seconds, if they had started to cross just before hearing those vehicles, they would have made it across before the vehicle reached them.

In Situations of Confidence for hearing, you can be confident that it is clear to cross ONLY WHEN IT IS QUIET, so you must be able to recognize when it is quiet! This is covered in Section 4, which is about preparing your students to be able to cross in Situations of Confidence. It discusses teaching them to recognize when it's quiet enough in Situations of Confidence to be confident that it is clear to cross.

** Many crossings are Situations of Uncertainty at certain times and Situations of Confidence at other times. This is true for everyone but it is especially a problem for people who use hearing to cross because, as will be explained later, the characteristics of sound that can change crossings from Situations of Confidence to Uncertainty may not be noticeable.

For example a crossing may temporarily be a Situation of Uncertainty because parked vehicles are blocking the sound of traffic, or the sound level of "quiet" is high (this will be explained later). At other times, that same crossing is a Situation of Confidence because the circumstances allow you to hear the approaching traffic with enough warning (such as when the roads are wet, or it's at night when the sound level of "quiet" is lower).

Therefore blind pedestrians should always observe the situation before crossing to determine if it is a Situation of Uncertainty or Confidence. They should not assume that it's "clear to cross when quiet" just because that was the case at another time.

Whether they use hearing or vision to cross, our students need to be able to (1) recognize and (2) deal with Situations of Uncertainty and Situations of Confidence. Section 2 is about teaching them to recognize the situations, Section 3 is about teaching them to deal with Situations of Uncertainty and Section 4 is about teaching them to deal with Situations of Confidence.

This will help them gain the life-saving "A" skills for "A"-students, as explained below.

Life-Saving "A" Skills Our students need the following skills: ALERT -- be Alert to recognize Situations of Uncertainty; ANALYZE -- be able to Analyze the level of risk in Situations of Uncertainty; ALTERNATIVES -- know about Alternatives and be able to use them when the risk of crossing is unacceptable; ASCERTAIN -- be able to Ascertain crossable gaps in Situations of Confidence.

Research -- are there really Situations of Uncertainty and Situations of Confidence?

In 2006, Dr. Rob Wall Emerson from Western Michigan University and I asked 22 blind people with normal hearing to sit in my mother's lawnchairs at 3 different sites, and raise their hand when they heard something that they thought might be a vehicle approaching them.

We studied primarily 4 things:  Detection-to-arrive time -- how many seconds passed from when one of the subjects first heard a vehicle until the vehicle arrived?  Level of ambient sound -- when the subjects heard the vehicle, was there any masking noise and if so, how loud was it?  Speed of vehicles -- how fast was the vehicle coming?  Sound level of vehicles -- how loud was the vehicle when it passed?

The sites we chose to study (pictured below) were all two-lane, quiet intersections with a speed limit of 25 mph (I'll explain later what I mean by "quiet intersections").

Site 1 was a street that is straight and clear of obstructions for at least a block in each direction, so the vehicles approached in what we called the "straight" approaches.

On half the trials at this site, we put up a barrier to block the sound (the "baffle" approach). Site 2 was the same crossing that Linda Sussman showed me and that you saw in the video on page 7. The street has a severe bend to the right (the "severe bend" approach) and a minor bend to the left (the "minor bend" approach).

Site 3 had a steep hill to the right (the "hill" approach) and trees to the left (the "trees" approach).

Research -- What did we learn from sitting in lawn chairs? If you want some good bed-time reading material to help you fall asleep at night, you can check out the full report of our research in the December 2008 Journal of Visual Impairment and Blindness (Detecting Approaching Vehicles at Streets with No Traffic Control). But that isn't necessary -- I'll tell you what we learned in a nutshell.

As you read the following results, keep in mind that the crossing time, based on the average walking speed of 4 feet/second, is almost 4 seconds for traffic from the left (which is on the first half of the street), and to get clear of traffic from the right would take 7 seconds.

Of the 6 approaches where subjects listened for vehicles:  Several approaches were Situations of Confidence. When it was quiet at both of the "Straight" approaches (crossing time almost 4 seconds for traffic approaching from the left and 7 seconds for traffic from the right) and at the "Trees" approach (crossing time for that traffic was almost 4 seconds), the subjects heard all the vehicles at least 7 seconds away (see Table 1 below).

This means that if pedestrians with normal hearing and an average walking speed had started to cross these approaches while it was still quiet, they could be confident that no vehicle from those directions was approaching that could reach them during their crossing (heck -- if there were such a vehicle coming, they could have heard it!).

 Several approaches were Situations of Uncertainty. To no one's surprise, even when it was quiet at the "sharp bend" approach (the site that Linda Sussman had found 22 years ago and which was shown on the videotape on page 7), the AVERAGE time from when subjects heard those vehicles until they arrived was only 5.22 seconds (the range was 4 to 19 seconds).

The crossing time for the average person there is 7 seconds, which means that more than half of the vehicles could not be heard until they were so close that if a pedestrian with average walking speed had started to cross just before hearing them (when it was still quiet), the driver would have had to slow down to avoid hitting the person. The "hill" approach (crossing time 7 seconds) was another Situation of Uncertainty, because some of the vehicles could not be heard until they were less than 7 seconds away(see Table 1 below).

Table 1: Time of detection to arrival for vehicles (heard when quiet)

Condition / site straight Baffle Minor bend Severe bend Hill Trees (no. of trials) (144) (50) (39) (60) (43) (24) Average (in secs) 12.02 13.24 12.45 5.22 7.58 12.31 Range (in secs) 7 to 35 5 to 32 4 to 28 4 to 19 4 to 20 7 to 26 What factors affected the subjects' ability to hear the vehicles? Of the 4 factors we studied, which do you think affected the subjects' ability to hear the vehicles the MOST? (ANSWER is in the review on the last page)  Level of ambient sound  Speed of vehicles  How loud was the vehicle itself  Presence of a hill, bend in the road, blockage, etc.

Of the 4 factors we studied, which do you think affected the subjects' ability to hear the vehicles the LEAST? (ANSWER is in the review on the last page)  Level of ambient sound Level of ambient sound  Speed of vehicles  How loud was the vehicle itself  Presence of a hill, bend in the road, blockage, etc.

It is important to note, however, that these factors altogether accounted for only a third of the variability in people's ability to hear the vehicles approaching.

That means that no single feature or even combination of features can predict that there will be a Situation of Uncertainty .

We concluded, therefore, that Pedestrians who are blind "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." Actually, this is true for all pedestrians. Whether they use their hearing or vision to cross the street, pedestrians need to observe how much time there is from when they can hear or see the vehicles until the vehicles arrive (detection-to-arrival time), and make sure it is at least as long as their crossing time. If they can't hear or see the vehicles well enough, they won't have enough warning that vehicles are coming -- they are in a Situation of Uncertainty. Page 11 of 22

So how can we recognize Situations of Uncertainty?

** The only way to determine if you are in a Situation of Uncertainty is to observe and analyze how well you can hear / see the traffic in that situation and make sure you have enough warning of their approach.

** Other than observing how well you can hear/see the vehicles, there are no rules or guidelines that reliably predict whether you are in a Situation of Uncertainty.

Not even rules that seem intuitive, such as "it is safe to cross when it is quiet IF the street is narrow and visible for a long distance and the traffic is slow."

I will illustrate this with a story. Many years ago, I was looking for a street-crossing situation for my client to analyze. She had already analyzed a situation that turned out to be a Situation of Uncertainty, so I was looking for a Situation of Confidence where she could hear the approaching vehicles with plenty of warning.

I chose the crossing in the photo to the left. It seemed perfect! The road was narrow (only 2 lanes), the speed and traffic volume were low, and there was nothing blocking the sound of traffic -- I could see the traffic approaching from quite a distance.

So I brought her there for our session. As she listened to the traffic to figure out how wide the street is, she quietly said, "I can't hear the cars well enough here to know if it's clear to cross."

That session was videotaped, and I still chuckle when I see my face showing the shock and disbelief that I felt when she said that. I thought, "This can't be true!" So I listened, and sure enough -- she was right! I could see the cars coming but neither of us could hear them until they were about 5 seconds away.

Anyway, if you can't take my word for it, find out for yourself -- go to the next page and see how well you can predict which of the situations in the "Uncertainty Prediction Challenge" show a Situation of Uncertainty for gap judgment. Page 12 of 22

Uncertainty Prediction Challenge

[NOTE: Participating in the Challenge requires that you go online to click on the links to see if you are correct.]

Welcome to our Challenge! If you are still convinced that it is possible to predict whether or not you are in a Situation of Uncertainty just by noticing the features of the crossing (such as hills or bends in the road, ambient sound level, etc.), OR if you want to see some dramatic examples showing that this is not true, this page is for you! But if you're already convinced and/or you don't have time, you can move on to the NEXT PAGE.

Okay, if you're still here and want to take the challenge, here's how it works. These pictures show real situations which have been analyzed by people listening for approaching traffic. In fact, some of them are the sites of extensive research, others are crossings which I analyzed with my clients. The streets are all two-way streets, and the photos each show a stick figure representing a pedestrian wanting to cross.

For each situation, we are only analyzing one direction at a time, not the whole crossing. Look at the situation in the photo, and see if you can predict whether or not people who have normal hearing and average walking speed would be able to hear the traffic coming from that direction with enough warning to be a Situation of Confidence. Click on the "YES" if you think that they could hear those vehicles well enough in this situation to be confident it was clear to cross whenever it was quiet. Click on the NO" if you think that traffic could not be heard well enough in this situation for people to be sure it was clear to cross, even when it was quiet.

PHOTO #1: (NE corner): Listening for traffic from the figure/person's left (from the east) -- have to cross two lanes to get out of their way. Speed limit: 55 mph

PHOTO #1: YES (can hear well enough) NO (can NOT hear well enough) PHOTO #2: (NE corner): Listening for traffic from the figure/person's right (from the west) -- have to cross all 3 lanes to get out of their way. Speed limit: 55 mph

PHOTO #2: YES (can hear well enough) NO (can NOT hear well enough)

PHOTO #3: (SE corner): Listening for traffic from the figure/person's right (from the east) -- have to cross both lanes to get out of their way. A vehicle is visible coming around a sharp left bend in the road. Speed limit: 25 mph

PHOTO #4: (SE corner): Listening for traffic from the figure/person's left (from the west) -- have to cross half the street to get out of their way. Speed limit: 25 mph

PHOTO #4: YES (can hear well enough) NO (can NOT hear well enough) PHOTO #5: (SW corner): Listening for traffic from the figure/person's right (from the east) -- have to cross the whole street to get out of their way. The street slopes gently down to the bend in the road, then slopes gently back up again. Speed limit: 30 mph

PHOTO #6: (NE corner, first condition): Listening for traffic from the figure/person's right (from the north) -- have to cross the whole street to get out of their way. Speed limit: 35 mph

PHOTO #7:

(NE corner, second condition): Listening for traffic from the figure/person's right (from the north) -- have to cross the whole street to get out of their way. Speed limit: 35 mph

PHOTO #7: YES (can hear well enough) NO (can hear well enough) Page 13 of 22

So how can we recognize Situations of Uncertainty?

If you took the Uncertainty Prediction Challenge, was it easy to predict when there is a Situation of Uncertainty? If you say, "No WAY!" then join the club!

And THAT is exactly the point! NO ONE can determine whether or not there is a Situation of Uncertainty just by noticing features of the crossing.

What I hope you learned from taking the Challenge is that:

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

The ONLY way to determine if you are in a situation of uncertainty for gap judgment is to observe and analyze how well you can hear / see the traffic in THAT situation!

#1. #2. #3

For example (photos above are from the Uncertainty Prediction Challenge): Sharp bend?  Photo #1 above -- a sharp bend in the road nearby DOES make a Situation of Uncertainty (we can not hear traffic beyond the bend).  Photo #2 above -- a sharp bend in the road nearby DOES NOT make a Situation of Uncertainty (we can hear traffic from far beyond the bend).

Speed of traffic?  Photo #1 above -- the traffic is slow but there IS a Situation of Uncertainty  Photo #2 above -- the traffic is fast but there IS NOT a Situation of Uncertainty

Constancy of situation?  Sometimes conditions can change, so that at one time, whenever it's quiet you can hear the vehicles with enough warning, but that's not true at another time. For example: o When the roads are wet, traffic can be heard better than when they are dry. o Installing a speed hump at the street in photo #4 above made it possible to hear well enough to know it is clear to cross whenever it is quiet. o Later in this Section you'll learn that at the crossing where Gordon Parks was killed, there was a Situation of Uncertainty during the day but not in the evening. o At the street in photo #3 above, parked vehicles created a Situation of Uncertainty because they blocked the sound of traffic. 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 much (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 either.

Long line of sight?  Photo #2 above -- Can hear the vehicles before they can be seen.  Photo #4 above -- Can see the vehicles before they can be heard.  Videos below -- Can see the vehicles long before they can be heard (videos taken by Rikkilyn and Paul Layher). In the Layher's first video below, you can see a car approaching from a quarter mile away on our left, but you cannot hear it until it is only about 5 seconds away (just before the student says "NOW"). In the second video [right, below] Rikilynn describes the situation and shows the street, which is very straight in both directions with no trees or other obstructions. The cars that we hear are all coming from the left. VIDEOS: Click here for the first video; Click here for the second video

I hope you understand now that: the only way to determine if you are in a Situation of Uncertainty is to . . . what? . . .

Answer: . . . observe and analyze how well you can hear / see the traffic in THAT situation and determine if you have enough warning! Page 14 of 22

But aren't there any strategies that can assure enough time for crossing these streets?

NO! Although a few strategies have been developed and used over the years, none of these have been verified as reliable. In fact, a few have been shown to be unreliable, and they could actually increase the risk of crossing.

One of these unreliable strategies is:  crossing with a car that is at a stop sign on the parallel street (as shown in the photo to the right)

This strategy:  does not assure enough clearance time to cross, nor does it provide any "buffer;"  can make it difficult for drivers to see you;  can make it more difficult or impossible to hear the traffic on the street being crossed.

If you want to read more about this strategy and experiments that indicate that it is unreliable, you can click here (this takes you outside of the Self-Study Guide).

Study Questions

WHEW! You've covered a LOT of material that conveys essential information! Before you proceed, you might want to take a break and make sure you understand this information -- these questions cover all the essential information you've learned so far.

1. What assumption about crossings with no traffic control is no longer true? (Review) What evidence do we have for this? (Review)

2. Are there situations today in which we can not be confident it is clear to cross even though it is quiet and we hear no vehicles approaching? (Review) Are there any situations today where we can be confident that it is clear to cross whenever it is quiet? (Review) 3. Are there any rules or guidelines for figuring out whether you are in a situation of uncertainty for gap judgment, other than observing how well you can hear or see the vehicles?(Review) That is, are there any features of intersections (such as hills and bends, width of the street, etc.) that can predict whether or not there is a Situation of Uncertainty for gap judgment? (Review)

4. Can we rely on crossing strategies such as starting to cross with a car that was waiting at the stop sign on the parallel street beside us? (Review)

What is "Quiet"? -- Varies between and within communities

Well, FINALLY I am ready to talk about what "quiet" means, as I had promised! Then we'll consider the effect of ambient sound when listening for vehicles.

"Residual sound level" In 1970, Wyle Laboratories went to 18 different locations and measured the level of sound during a 24- hour period. The locations ranged from a farm next to the Grand Canyon to a New York City window overlooking a highway.

They noticed that in each site, when all sounds had died down, there still remained what they called "residual noise level" -- that is, the sound level of what we would call "quiet." As they described it, residual noise is "the continuous noise one hears in the backyard at night when no single source can be identified, and which seems to come from 'all around' " (Wyle Laboratories, 1971, page 7).

To no one's surprise, they found that the residual noise level varies between communities -- "quiet" was louder in New York City than it was on the farm. What is surprising is that it also varies during the day in each location.

Varies between communities: The daytime sound level of "quiet" (residual noise level) for various communities was as follows:  Quiet suburban residential: 36-40 dB(A)  Urban/suburban residential: 42-56 dB(A)  Cities: 62-69 dB(A).

The range of the sound level of "quiet" for these communities is extraordinary, when you consider that the decibel system is logarithmic, so each increase of 10 decibels means doubling the level of sound. The residual noise level of "quiet" in cities was almost 30 decibels noisier than for suburban residential communities, so their sound level of "quiet" would be perceived to be almost 8 times as loud.

Apparently, the sound level of "quiet" is the same today as it was in 1971. When Dr. Rob Wall Emerson and I did our research in 2006, we measured the sound level of "quiet" during the middle of the day in various communities (Wall Emerson & Sauerburger, 2008) and found that the range of residual sound level for  suburban Silver Spring intersections was 37 to 49.5 db(A);  urban / suburban Annapolis intersections was 45.5 to 53 db(A); and  the city of Atlanta was 63.5 to 69 db(A).

Varies during the day: The residual noise level at each site varied during the day, being loudest at about 4:00 PM and quietest at about 4:00 AM. A sample of the range of residual noise level (sound level of "quiet") in a typical residential community was recorded as follows:

Typical Residential Community 2:00 AM ~30 db(A) 8:00-9:00 AM ~42 db(A) 4:00 PM ~48 db(A) Evening ~45 db(A)

Again, the range in the sound level of "quiet" over time at the same location is remarkable. There was a difference of almost 20 decibels from the quietest time of the day to the noisiest, which means that "quiet" in the middle of the day at that location would be perceived as 4 times as noisy as it was in the middle of the night.

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

Wyle Laboratories (1971). Community Noise. U.S. Environmental Protection Agency, Office of Noise Abatement and Control, Washington, DChttp://www.nonoise.org/epa/Roll14/roll14doc65.pdf

What is "Quiet"? -- Effect of changes in ambient sound

As you already learned from the research that Dr. Rob Wall Emerson and I did, the factor that most impacted the ability of the blind subjects to hear vehicles was the ambient sound. Let's look at those results more closely, in view of what I explained on the last page about residual noise levels (the sound level of "quiet") in various communities and at various times of the day.

The graph below shows the effect of the ambient sound level on the subjects' ability to hear the vehicles at our research site where the street had no bends or hills or barriers (for a verbal description of the graph, click here). The vertical axis shows how many seconds passed from the moment that the subjects heard the vehicle until the vehicle arrived (the detection-to-arrival time), and the horizontal axis shows how loud was the environment when they heard the vehicle (for example, was there noise from a lawnmower, airplane, receding traffic, etc.). The pink line shows the average of the vehicle detection-to- arrival times.

Notice that as the ambient sound got noisier, it became more and more difficult to hear the approaching vehicles.  When it was very quiet (37 db(A) or less), all the vehicles were heard more than 8 seconds away.  At 49 db(A), the pink line indicates that average vehicles were not heard until they were less than 8 seconds away.  At 55 db(A), none of the vehicles could be heard more than 8 seconds away.

Now consider the fact that in cities, the residual noise level (the sound level of "quiet") during the day is more than 55 db(A). What does that tell you about the ability of blind pedestrians to hear the approaching vehicles when it is "quiet" in the city? They are likely to be in a Situation of Uncertainty during the day because they probably cannot hear approaching vehicles until they are too close. And consider that the residual noise level varied during the day at each site. For example, the last page gave you a sample from a "Typical Residential Community" where the sound level of "quiet" at night was about 30 db(A) and in the afternoon it was about 48 db(A). According to the graph above, when the ambient sound was less than 38 db(A), the subjects heard all the vehicles at least 10 seconds away, but when it was 48 db(A) at the same site, half the vehicles could not be heard until they were less than 10 seconds away.

So what would happen if our research site has the same variation in "residual noise level" that the typical residential community had? That would mean that at night, when the sound level of "quiet" is 30 db(A), pedestrians whose crossing time is 10 seconds could be confident that it is clear to cross when quiet (if there was a vehicle less than 10 seconds away, they would have heard it). But in the afternoon at that same crossing, they would probably be in a Situtation of Uncertainty because when it was "quiet," the ambient sound level would be about 48 db(A) and at that level in our research, half the vehicles could not be heard until they are less than 10 seconds away.

This effect of variation in the sound level of "quiet" may explain the difference in the ability to hear traffic at different times of the day at the crossing where Gordon Parks was killed (this is explained later in this section).

What is "Quiet"? -- Effect of slight increase of ambient sound

The graph to the left shows how the level of ambient sound at each of the 6 approaches affected the ability to hear the vehicles at that site (for a text description of the graph, click here). The horizontal axis shows the increase in ambient sound, and the vertical axis shows the average time from detection of vehicles to their arrival (in seconds).

I noticed something strange while teaching people to recognize if they are in a Situation of Uncertainty.

In some places, a slight increase in background ("ambient") noise such as from distant lawnmowers and airplanes seemed to have little or no effect on how well we could hear the vehicles approaching. But at other places, the slightest noise drastically cut back on our ability to hear the vehicles, so that we were unable to hear them until they got much closer.

As a result, I began to teach people that when they are in situations where they can hear traffic with enough warning when it is quiet, they should notice whether they can still hear it as well when there is a little background noise. In other words, evaluate how much ambient sound they can tolerate (how "quiet" it has to be) and still hear well enough to be in a Situation of Confidence.

The research that Rob Wall Emerson and I did seemed to validate my observation:  The chart above shows that for every approach except the hill, increasing the ambient noise as much as 5 db(A) didn't have much effect -- people could still hear the cars just as well. That is, as the ambient noise went from 36 to 40 or even 42 db(A), detection time fluctuated up and down and back up again before it started to go down permanently.  It was a different story at the hill approach, however. When the ambient sound level was 38 db(A), the vehicles approaching from the hill were heard an average of 13 seconds away, but when the ambient sound was increased only 2 db(A), rather than fluctuate up and down, the detection time was reduced to about 9 seconds, and then it continued to plummet as the ambient sound became louder than 42 db(A). (Pictures of the approaches are below.)

baffle straight

minor bend severe bend

trees hill Page 19 of 22

Situations of Uncertainty . . . does it really matter?

We have been talking about Situations of Uncertainty and how to recognize them, as well as the reliability of the traditional strategy "Clear to cross when quiet" and what "quiet" really means. Let's take a look at how this applies to real-life situations.

Sue Etters and her guide dog got off the bus every day for 15 years to get home from work. She crossed Beaver Avenue where thers is no stop sign or traffic signal -- the street was only two lanes wide there. Sue, who is totally blind, had been taught by her O&M specialist in the 1960's that it is clear to cross when quiet.

Starting in July, 2009 Sue no longer used her dog, and crossed there every day using her cane. Less than 6 months later she was hit by a car and almost killed while crossing there.

Thankfully, she lived to tell about it, as she does in the video to the right (the link to this YouTube video may not be accessible from restricted sites). You can click here for information about the crossing and what happened there.

Noticing hints of a problem Was there any way to predict and avoid this calamity, any hints of a problem? Well . . . yes there was, though it wasn't recognized at the time.

Over the years, she had noticed that sometimes when she crossed, her guide dog stopped or pulled back in order to avoid being hit by a car that she hadn't heard when she started to cross. She later told me that these cars that sneaked up on her were not "quiet cars" -- when they went by her, they were as noisy as any other car.

But it never occurred to Sue that this indicated there might be a problem with her use of the strategy "cross when quiet" there. Even several months after her clash with death, Sue didn't realize why that car was able to reach her when she hadn't heard it when she started crossing.

So I told her about Situations of Uncertainty. I explained that regardless of how skilled and careful you are, when you are in a Situation of Uncertainty you can't be sure it is clear to cross, even when it is very quiet. Lessons learned?

Sue learned that before she crosses any street where is no stop sign or traffic signal, she should first listen to figure out whether she can hear the traffic with enough warning, or is in a Situation of Uncertainty. She said she will never again cross in situations where there is so much risk, and will learn how to recognize Situations of Uncertainty.

But this understanding didn't come naturally -- we cannot assume that people learn this from experience. Our students need to know that there are situations where the "cross when quiet" strategy is no longer reliable, and learn how to recognize and deal with them.

What is our responsibility?

Sue said it best: "It's almost like playing Russian roulette. I'm not scared and I will travel independently again but I want to do it safer than I did before, and recognize where it is too dangerous. What happened to me happened for a reason, and I'm glad I'm around to talk about it. I don't want ANYONE to have to experience what I did. Mobility instructors all need to tell their students about this, so they know that they risk being injured or killed in these situations."

Tragically, just 3 days after this interview, another blind traveler crossed at another Situation of Uncertainty. He was also hit but, unlike Sue, he was killed. On the next page we'll look at what happened.

Another Tragedy -- Can We Learn any Lessons?

At 9:30 Thursday morning, October 7, 2010, Gordon Parks and his guide dog Wendy were walking from their home to downtown Moorestown in the New Jersey suburbs just outside of Philadelphia. They had to cross Camden Avenue, a two-lane street with fast traffic.

Less than a 5-minute walk away, they could have crossed at a traffic signal with Accessible Pedestrian Signals that had been installed at Gorden's request several years earlier. However Gordon thought that crossing at the signal was too risky because of the turning cars, so they usually crossed where there was no stop sign or traffic signal (see photo to the left). This morning, Gordon was wearing an orange vest to make the crossing safer.

Just as they entered the second lane, they were hit by a Dodge Ram pickup truck coming from their right. Gordon was thrown back and died the next day, his dog Wendy was killed immediately. The driver said he never saw them-- they may have been hidden by the truck's windshield frame. Three weeks after the tragedy, I went to the intersection to analyze the situation.

Situation of Confidence sometimes; Situation of Uncertainty sometimes

I evaluated the situation at that crossing using hearing, which is what Gordon used. The first time I analyzed it (about 3:00 Friday afternoon), it was clearly a Situation of Uncertainty. The second time I analyzed it (Saturday evening at about 8:00), it was clearly a Situation of Confidence. (You can click here if you want more details of the analysis.)

I made the video to the right on Friday afternoon while I stood where Gordon and Wendy had started their crossing (the link may not be accessible from restricted sites). When the video begins, it is quiet and no vehicles can be seen in either direction, and yet it is not possible to hear a pickup truck approaching from the right until it is about 4 seconds away.

For someone like Gordon who relies on hearing to cross, this would be considered a Situation of Uncertainty because even when it seems quiet, it isn't possible for anyone to hear the vehicles well enough to be sure whether or not it is clear to cross.

However at 8:00 the next evening at the very same crossing, whenever it was quiet, I could hear all the traffic from several blocks (at least 13 seconds away).

Commitment to Prepare Students Sue and Gordon were each hit while relying on the strategy "cross when quiet." Sue didn't know what a Situation of Uncertainty is, even after she was hit. We'll never know whether Gordon realized that at certain times of the day, he was crossing in a Situation of Uncertainty, nor what would have happened if the risks of crossing there had been analyzed and compared to the risks of crossing at the signal (we will cover how to analyze risks of Situations of Uncertainty in Section 3).

We should prepare all our students who may, at some time in their lives, face situations and have to make decisions similar to the ones Sue and Gordon faced. If we avoid the issue by simply telling our students not to cross where there is no traffic control, or that it is always safer to cross at a traffic signal, or tell them that every crossing is a Situation of Uncertainty, we are leaving them unprepared to evaluate situations and make decisions based on good analysis and information. The fact is, there are many Situations of Confidence at streets with no traffic control; many instances where crossing at the traffic signal is not the safest way to get across a street; and many Situations of Uncertainty where the risk of crossing is acceptable -- each situation should be analyzed and our students need to be able to do so.

Let's learn from these tragedies and commit ourselves to provide our students with strategies so THEY CAN:  recognize Situations of Uncertainty;  analyze how much risk is involved in each crossing so they can make the best decisions based on their own information-gathering and assessment;  realize that some crossings may involve unacceptable risk; and  be empowered with viable alternatives for crossings that have more risk than they are willing to accept. (Each of these is covered in detail in the Self-Study Guide.)

It is our responsibility to prepare our students with these skills, according to the members of AER's O&M Division, the largest O&M professional organization in the world.

O&M Best Practice In 2008, the AER O&M Division approved a position paper which says: "Although this strategy of crossing when quiet still is reliable in some situations, research and observations indicate there are situations where it is not possible for a person with normal hearing and walking speed to hear traffic with sufficient warning to be assured that there is a gap in traffic long enough to cross even when it is quiet (Wall Emerson & Sauerburger, 2008, Sauerburger, 1989, 1995, 1999, 2006, Snook-Hill and Sauerburger 1996)."

This position paper, which is the consensus of the O&M profession, explains that

best practice for O&M programs is to prepare students to be able to "recognize situations where they cannot hear or see well enough to reliably predict gaps in traffic" [that is, recognize situations where they cannot predict when it is clear to cross]. AER O&M Division position paper, 2008

Teaching our students about crossings with no traffic control The remaining sections of the Self-Study Guide address how to teach students to  recognize Situations of Uncertainty, and Situations of Confidence (Section 2);  analyze the risk of crossing at Situations of Uncertainty, and use alternatives when the risk is unacceptable (Section 3);  be able to reliably determine crossable gaps in traffic at Situations of Confidence (Section 4). Page 22 of 22

Review

Congratulations, you have completed the first section of the Self-Study Guide! We discussed crossings with no traffic signal or stop sign and you learned that when using hearing to cross  the strategy "clear to cross when quiet" is still reliable in many situations (Situations of Confidence) but  at some crossings, there are Situations of Uncertainty where you cannot be certain there is a crossable gap in traffic because you don't have enough warning of approaching vehicles.  there are no simple rules for determining if you are in a Situation of Uncertainty, and the situation can change at any given crossing.  the only way to determine if you are in a Situation of Uncertainty is to observe how well you can hear / see the approaching vehicles at that moment.  the ability to hear the approaching vehicles with enough warning is most affected by ambient sound and least affected by the sound of the vehicles themselves.  the sound level of "quiet" changes during the day and varies among communities.  The consensus of O&M specialists is that they are responsible to teach their students to recognize Situations of Uncertainty and deal with them.

For many people, this first section is the most difficult, as it requires the understanding of a very complex issue and, for some, a paradigm shift. The rest of the Self-Study Guide is about teaching students to recognize and deal with Situations of Uncertainty and, when they are not in a Situation of Uncertainty, to figure out when it's clear to cross.

Please note that while this Section 1 dealt primarily with recognizing Situations of Uncertainty using hearing, it is just as important for people who use vision to be able to recognize Situations of Uncertainty. The rest of the Self-Study Guide will address those who use vision as well as those who use hearing to cross.