JVIB, September-October 1995
SAFETY AWARENESS
FOR CROSSING STREETS WITH NO TRAFFIC CONTROL
Dona Sauerburger
During the first 15 years that I taught orientation and mobility (O&M), I assumed that people who are visually impaired can safely cross streets that have no traffic lights or stop signs if they do so when they do not hear or see traffic approaching. Apparently, this is a common assumption, even in textbooks (see, for example, Jacobson, 1993; LaGrow and Weessies, 1994). This assumption is probably based on techniques derived from practice-based knowledge developed in the 1940's, when there were louder car engines, less traffic congestion, and fewer streets wider than two lanes.
I also assumed that most visually impaired people do not need to be taught to recognize whether or not they can detect traffic or judge the speed and distance of traffic well enough to cross safely. This also seems to be a common assumption, since the O&M programs described in Hill and Ponder (1976), Jacobson (1993), and LaGrow and Weessies (1994) do not address how to teach people to make this judgment.
I began to question these assumptions in 1987, when a blind man, his visually impaired wife, and his guide dog were killed one night while crossing a six-lane street that had no traffic control. Both people routinely crossed there alone, and because they were cautious, responsible people, they probably would not have done so if they had not assumed that they could recognize when it was safe to cross.
Because of the difference in their vision, when they crossed that street alone, each of them probably encountered one of two distinct situations that are typically faced by most travelers, blind or sighted, who cross streets where there is no traffic control. The woman, who apparently had good functional vision, probably crossed even though she saw headlights of approaching vehicles because she judged that the nearest car was still far enough away or slow enough that it would not reach her before she reached the other side. The ability of the man, who was totally blind, to detect vehicles was limited.
To cross safely in this situation, people need to know if they can hear the traffic well enough to assume that when it is quiet, it will be safe to cross.
To analyze whether I could determine when it was safe to cross the street if I relied on hearing alone, I determined that it took me 8.5 seconds to cross from the median strip to the curb that the man and woman were trying to reach and then recorded how long it took cars to reach me once I heard them during a quiet lull. Although I have normal hearing, when it was quiet, I was unable to hear some of the cars until they were only three seconds away. My conclusion was that at that intersection, I could not assume it was safe to cross when it was quiet because I could not hear all the cars that might have reached me during my crossing. This method of analyzing a person's ability to detect vehicles, called the Timing Method for Assessing the Detection of Vehicles (TMAD) (see Sauerburger, 1989) is described in Box 1.
During the last seven years, I have used the TMAD to help dozens of people determine if they could detect approaching vehicles sufficiently to know when it was safe to cross particular streets. Although in most instances the traffic could be detected sufficiently to cross safely, in many situations, approaching traffic could not be heard or seen well enough, so it was not necessarily safe to cross when no approaching traffic was detected. In some of these instances, the clients required a lot of time to cross because of the width of the street or a mobility impairment or because their ability to hear or see the traffic was impaired because the sound or view was obscured or they had impaired hearing and vision. However, even on a few two-lane residential streets, clients who had good hearing and who could walk quickly could not hear the traffic well enough to know whether it was clear to cross when it was quiet and there were no masking sounds.
Teaching safety awareness when the ability to detect traffic is limited
All travelers who cross areas where uncontrolled traffic passes must be able to recognize when they can detect the vehicles with ample warning, and when it is not possible to do so. Clients must be aware that they should observe and make this determination before crossing, rather than assume it is always safe to cross when they do not hear or see approaching traffic. Even at familiar streets that are normally safe, they should be able recognize when conditions are such that they cannot tell when it is safe to cross (such as when traffic sounds are blocked by a parked truck or masked by wind, rain or noises or visibility is reduced because of glare, fog, rain, or poor lighting conditions).
Using feedback from the TMAD at a variety of intersections helped my clients and me improve our ability to observe and judge the safety of crossing streets without traffic control.To be able to judge one's ability to detect traffic accurately during travel without having to stop and make formal assessments is actually more important than simply assessing specific situations because with reliable judgment, one can quickly and accurately assess any situation one encounters.
Clients can be trained to evaluate streets without traffic control when they are ready to learn to cross busy intersections, either before or after they learn to cross those with traffic lights. Because numerous approaching vehicles, as well as lulls in traffic, are needed for the training, it is best to teach clients at streets that have relatively frequent but sporadic traffic. For example, for clients who rely on hearing and who probably would not cross these streets when they hear traffic approaching, one cannot use streets that are so busy that there is never a quiet break in traffic because there would be no time when such clients might think it would be safe to cross.
The same procedure for training can be used with clients who rely exclusively on hearing, those who rely on both hearing and vision, and those who are deaf and rely on impaired vision. One should begin training by explaining to the client that there are many situations in which it is not possible to hear or see the traffic well enough to know when it is safe to cross and that the purpose of the session is to assess and develop the client's ability to recognize those situations. It is important never to set out to "prove" anything to a client because one cannot predict what the instructor and client will discover and conclude from the session, and instructor does not usually know exactly what the client sees and hears in a particular situation.
If clients are not familiar with the street, they should first determine its approximate width, either visually or by listening to how far away the vehicles are in the farthest lanes. Then, they should use whatever they would normally use to observe the situation (vision, hearing, or both) to judge whether they can detect the vehicles well enough to know when they can cross safely. After they have looked or listened for a while, they make their pronouncement that either they can or cannot detect the vehicles well enough in this situation. Then the instructor uses the TMAD to test their judgement and provide feedback. The instructor should repeat this procedure under a variety of conditions, including situations when it is not possible to detect the vehicles well enough, until the clients seem to be able to judge accurately whether they can detect the traffic well enough to cross safely.
Getting feedback from the TMAD also teaches clients about the effects of various conditions. For example, those who depend on hearing but who are not aware of how noises can mask the sound of approaching cars often start to time their detection of an approaching car during what they consider to be a quiet lull when, in fact, there is noise from airplanes, receding cars, wind, and so forth. Usually the timing of their detection shows that they did not detect it from far enough away or that they detected it much later than they did other vehicles. This situation is a good opportunity to point out that when they first heard the car, there was a particular noise that significantly reduced their ability to hear the car. After several such incidents, clients usually become much more astute in recognizing conditions in which they can or cannot detect vehicles well enough, and are aware of the masking effect of sounds that they had not noticed before.
Some students have difficulty recognizing whether or not a masking sound is loud enough to be a problem. Their judgment can be improved by having them try to guess whether the traffic sounds can still be detected sufficiently while a certain sound is present and then providing feedback about their judgment by testing it with the TMAD while the sound is still present. The instructor can either take advantage of steady environmental sounds, such as lawn mowers, or create the sound by leaving a car's engine running nearby or using a tape recording of a vacuum cleaner. After testing their judgement, have them move toward or away from the sound source or alter the volume and test their judgment again until they can accurately judge how much noise is too much for the situation. If necessary, repeat this procedure in other situations.
Those who rely on vision often describe which qualities make specific cars easier to see than others ("When the sun glares on their windshields I can see them quite far off," or "Light-colored cars are much harder for me to see"). They need to time their detection of the hard-to-see cars until they time at least one which is not only difficult to see but fast, so they can determine whether those cars are detected sufficiently or whether such cars could remain undetected until too late. Afte using the TMAD, many people who ascertain that their vision is not sufficient will consider using their hearing, and vice versa.
Often when a vehicle is difficult to detect, clients won't start the timer ("Oh, I didn't time that one because I didn't see [or hear] it till it was so close!"). I emphasize that I am trying to determine the worst-case scenario, and want to know if they can detect all vehicles sufficiently, particularly those that are hard to detect. If clients wait to start the timer until they are certain that what they see or hear is a vehicle, I tell them to start timing anything that may be an approaching vehicle, and encourage them to report false alarms.
Alternatives when one cannot detect traffic sufficiently
When clients realize that there are situations in which they cannot determine when it is safe to cross, they often ask, "What do I do if I want to get across a street when I judge that I can't see [or hear] well enough to know when it is safe to cross?" One solution is to find another place where it is possible to hear or see the traffic well enough. For example, often when the sound or view is blocked by such obstructions as a bend in the road or a parked truck, the client may be able to hear or see well enough if he or she stands farther from that obstruction.
When clients can detect vehicles sufficiently to know when it's clear enough to cross only half the street, it may be safe for them to start crossing if they turn back when they detect an approaching vehicle before they get halfway across, so they still have enough time to return safely. If they detect nothing by the time they reach the middle they know they have enough clearance to safely finish crossing the other half of the street. If a client chooses this strategy, be sure that he or she can go through with it and not panic or try to run across.
When clients cannot hear or see well enough to know when it is clear enough to start a safe crossing, they must decide if they want to accept the risk of crossing there alone or use safer alternatives, such as getting assistance, avoiding the crossing, or petitioning to have a traffic signal installed. If they choose to avoid the crossing, they can travel another route or using a paratransit van, taxi, or carpool; if the client must get to or from a bus across the street, he or she can sometimes avoid crossing the street by riding the bus to the end of the line and back.
Some people choose to accept the risk of crossing even though they know they cannot tell when it's safe to cross. They hope that either it will be clear when they cross or that the drivers of the vehicles that they do not detect will see them and slow down. The instructor should make sure that they are understand the risks they are undertaking in crossing under these conditions.
Assessing and developing judgement of speed and distance of vehicles
When people can detect the traffic sufficiently far that they could cross even when they know that vehicles are approaching, they must be able to judge how far away and how fast those vehicles are, compared to how much time they need to cross in order in order to determine if it is still safe to cross. To assess the ability to make this determination, I developed the Timing Method for Assessing Speed and Distance of vehicles (TMASD) (see box #2). I have used the TMASD with about a dozen people who have visual impairments, as well as with people who have normal vision.
Many people, including those with normal vision, may think it is safe to start walking across a street when the traffic is actually too close or fast. But after about a half hour of feedback from the TMASD, most clients improved, so they could accurately judge when they could safely start walking across.
However one client did not improve even after practice and feedback with the TMASD. Although she and her sister both had retinitis pigmentosa, her sister, whose acuity and visual field were much more limited than hers, had quickly learned to judge the traffic's speed and distance in the same conditions. Perhaps this woman was unable to do as well as her sister, even though she had more functional vison, because her depth perception was poor. Therefore it is essential that people who cross streets when they see traffic approaching learn to judge accurately when there is enough of a clearing to cross safely and that people who cannot do so because of impaired acuity or depth perception realize their limitations.
Alternatives when one cannot judge vehicles' speed and distance:
When people who are able to see traffic from afar cannot judge its speed and distance, they need to cross either when they see no approaching vehicles or when they know that the nearest car is no closer than a certain distance that they have determined is far enough. They can determine the distance by using a version of the TMAD, and gauge the distance by using such landmarks as bends and hills in the road, buildings, and trees.
For example, the client whose judgment did not improve decided it might be safe to cross if there were no cars between her and a certain driveway that she saw along the road. She tested this judgment by timing cars from when they passed the driveway until they reached her, and sure enough, even the fastest car would have allowed her time to finish her crossing if she had started to cross when it was just beyond that driveway.
Case examples:
The following are some examples of how the TMAD, TMASD, and other assessment and teaching strategies were used to help clients become more aware of their abilities and safety and better able to make decisions about crossing streets with no traffic control. These sessions were conducted before I learned the importance of clarifying the purpose of the session beforehand.
Example 1:
A 28-year-old man was concerned about crossing streets because he could not see cars from more than about a half block away. Near the end of his O&M program, we had a session at a moderately busy, two-lane residential street with no traffic control. He could see the width of the street, and I asked him to listen to the traffic to find out if he could hear it from far enough away to know it would be safe to cross when it was quiet.
When there was a pause in the traffic but a loud airplane was flying overhead, he announced that it was a good time to cross. I explained that what I wanted to know is, did he think that he could hear the cars well enough to know that it would be safe to cross at such a "quiet" time. As I finished talking, we heard a distant car from our left approach and then pass us, and he became concerned because he heard the cars behind it only a second or two before they reached us. Because he had no idea why this was so, I explained how the sound of receding vehicles can mask that of those that are approaching. After observing with this new awareness, he said he felt that when it was quiet, he could hear vehicles from far enough away that he would know it was safe to cross.
We then tested his judgement by using the TMAD, beginning with timing him as he crossed several times when I said it was safe. During one crossing he returned to the curb because he heard a car coming; the longest time for his completed crossings was 6.5 sec. As we stood on the curb again, I asked him to wait until it was quiet enough to cross, then start my stopwatch when he heard anything that might be an approaching car, and stop the watch when the car reached us.
He heard most cars much more than 6.5 seconds away, but one he did not because he heard it and started the timer when there was another airplane overhead. He was surprised at his failure to hear well enough, because he had thought that sounds which were unrelated and easy to distinguish from traffic sounds, such as airplanes, wouldn't affect his ability to hear the cars. I emphasized that all sounds, including lawn mowers, rustling trees, wind, or rain, will mask to some degree. However, several more demonstrations (with feedback from the TMAD) of the effect of various noises on his ability to hear the cars were required before he understood and seemed fully convinced.
We continued timing his detection of vehicles and concluded that, as he had predicted, when it is quiet he could consistently detect them sufficiently because he heard all of them when they were more than 6.5 seconds away. He noticed that my van, which was parked to our right, was muffling the sounds of cars significantly (they became suddenly audible when they emerged from behind the van), which may explain why absolute quiet was needed to hear them.
We then went to a moderately busy, five-lane street which he would have to cross to get to his bus stop. After listening carefully to the traffic, he guessed that when it is quiet, he might be able to hear the vehicles well enough to cross if he walked fast. Walking as fast as he could (almost running), he crossed it in 7.5 seconds. When we timed his detection of the cars, although he could indeed hear most of them from far enough away when it was absolutely quiet, one car from the right passed in front of us only 6.6 seconds after he first heard it during a quiet time. If he had started to cross at that quiet time, that car might have reached him just before he finished the crossing.
During our subsequent discussion, we noted that he had misjudged; he hadn't heard all the cars from far enough away to make it across even if he almost ran. We then considered that since he could hear the traffic well enough to cross more than halfway, he could start to cross during a lull in the traffic, then turn around if he heard a vehicle approach before he reached the middle of the street. I knew he could and would turn around if needed because he had done it when crossing at the last intersection.
As a result of this session, he was beginning to realize that in some situations he is unable to hear the traffic well enough to know when it is safe to cross, and was starting to notice when traffic sounds are muffled or masked too much. This session was followed later by sessions at other intersections to improve his ability to distinguish whether conditions are such that he can cross safely.
Example 2: [see vignette #4]
A man with retinitis pigmentosa has a visual field of about 5 degrees. If he takes a bus home from work, he has to cross an exceptionally busy two-lane street at night, when he is unable to see anything except lights. We went to that street one night for a session.
When asked whether he would cross by looking or listening, he said both; when he saw no vehicles approaching from the left, he would turn and watch for a clearing on the right while listening for cars from his left. There was a bend in the road a quarter mile to his left, and he felt that he could start to cross even if he saw a car just coming around that bend. To his right he could see vehicles at quite a distance, and felt that he could judge when they were still far enough away that he could cross.
After determining that he needed almost 6 seconds to cross the street, we first tested his judgement about cars from his left. The TMAD showed that he was right -- no car reached him in less than 7 seconds once he saw it come around the corner, and he only needed 3 seconds to cross the first half of the street.
We next tested his judgement of the speed and distance of the cars approaching from the right, using the TMASD. I asked him to start the timer at the last moment that he thought the approaching cars were still far enough away for him to cross. He did so for a variety of vehicles, and always started the timer when they were at least 8 seconds away. We concluded that with his present vision, he could determine the speed and distance of the traffic at night well enough to judge when it was far enough away that he could cross.
We then discussed whether he could depend on his hearing there for cars from the left. I asked him to close his eyes and notice if he could hear the cars from far enough away to detect them sufficiently. He was amazed that because of the constant sound of receding cars, he usually could not hear approaching cars until they were almost upon him. He then decided that when he noticed a clearing on the right, rather than depending on listening for cars from the left, he should glance to the left again before starting to cross. Since many people with severely restricted visual fields or impaired central vision cannot depend on glancing, we tested whether his glancing would be sufficient. This was done by having him repeatedly turn his head to glance, then immediately look away and report if he had seen any vehicles. We found that he could consistently and accurately detect the presence or absence of vehicles by glancing.
This man now feels confident that he can come home at night himself. We plan to have other sessions at this and other intersections during the day or at dusk when he cannot rely on headlights, to see if he can still judge the traffic's speed and distance as reliably.
Example #3: [see vignette #5]
A young man had received O&M training as a teenager when he had good functional vision, and now that he was totally blind he wanted a comprehensive review of his skills. Toward the end of this training, we went to a busy residential, two-lane, winding street which he had crossed often as a child.
As we stood at the curb, I asked him to listen and consider whether he could hear the cars well enough to cross there. At a quiet moment he said, "I would cross now." I explained that I didn't want to know when it was safe to cross, I wanted to know if he could hear the vehicles well enough there to know it was safe to cross when he heard no traffic coming. He listened again and said that he felt it would be safe to cross there when it was quiet.
When we used the TMAD to test his judgement, however, he was astonished to realize that though he could hear cars from the left almost three times as far as needed, he couldn't hear them from the right from far enough to get even half way across. He was incredulous that he couldn't tell when it was clear to cross, and thought that with practice and more O&M training he could learn to hear the traffic better. I explained that there are many intersections such as this, where it just isn't possible to hear (and in this case I also couldn't see) traffic well enough to know when it was clear to cross. He then suggested we try it again from a block to our left, where I again asked him to listen and decide if he could hear well enough there.
This time he observed carefully, having learned that he can't assume it is always safe to cross when it is quiet. He felt that there was still enough warning from cars to his left even though he couldn't hear them as well as before, and that cars from the right could now be heard from further away -- just enough, he thought, to know it would be safe to cross when it was quiet. The TMAD showed that this time he was right--cars from the left were heard about twice as far as needed, and cars from the right were detected at least a second further than needed to cross which was, as he had predicted, just barely enough time. He said that now, when planning to cross streets with no traffic control, he will first listen to notice whether he can hear the traffic from both sides well enough to know it would be safe to cross when it is quiet.
References
Hill, E., & Ponder, P. (1976). Orientation and mobility techniques; A guide for the practitioner. New York: American Foundation for the Blind.
Jacobson, W. (1993). The art and science of teaching orientation and mobility to persons with visual impairments. New York: American Foundation for the Blind.
LaGrow, S., & Weessies, M. (1994) Orientation and mobility: Techniques for independence. Palmerston North, New Zealand: Dunmore Press.
Sauerburger, D. (1989). To cross or not to cross: Objective timing methods of assessing street crossings without traffic controls. RE:view. 21, 153-161.
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