Practice Report -- JVIB, July 1999
Developing Criteria and Judgment of Safety for Crossing Streets with Gaps in Traffic
Dona Sauerburger
There are many situations in which people must cross streets or lanes during a gap in traffic because the vehicles passing there have no traffic control. Examples are intersections where only one street has stop signs and one wants to cross the other street, and right-turning lanes separated with an island at intersections with traffic signals.
Apparently in the 1940s, when the profession of orientation and mobility (O&M) was being developed with blinded veterans of World War II, it was safe to cross in these situations whenever no traffic could be heard approaching. According to Stanley Suterko (personal communication, 1998), who helped develop the O&M profession, a strategy similar to that of the Timing Method for Assessing the Detection of Vehicles (TMAD) was used in the 1940s and 1950s to prove to apprehensive O&M students that they could safely cross these streets when it was quiet. That is, an O&M instructor measured the time that a student needed to cross the street and then measured the time from when the student first heard a car until the time that the car reached the student. If the time it took for the cars to arrive was longer that the time it took to cross, it showed the student that he could hear approaching vehicles with enough warning time to get across the street.
This procedure was done at intersections in both residential and small business areas. At that time no intersection was encountered at which a student could not hear the vehicles well enough to know when it was clear to cross (personal communication with Suterko, 1998), probably because cars were easier to hear than they are today, and few streets were as wide as many are now.
Today, at many streets that have no traffic control, there is not always a sufficient gap in traffic whenever no traffic is heard to be approaching. Some of these streets are at residential intersections with only two lanes.
O&M students need to recognize these situations, and O&M instructors need to have functional criteria of safety that the students can use to make accurate judgments of whether the conditions allow them to cross safely during gaps in traffic. However, textbooks for O&M instructors (Allen, Courtney-Barbier, Griffin, Kern, & Shaw, 1997; Jacobson, 1993; LaGrow & Weessies, 1994; Pogrund et al., 1993) simply advise students to start crossing these streets when there is no approaching traffic or no sounds of traffic, without specifying in which conditions it would be possible or safe to do so.
O&M instructors need to develop and use criteria that are well defined, quantifiable, and that take into consideration the variations in people's hearing, vision, and speed of walking, as well as environmental factors that affect their ability to cross streets safely. Most important, criteria are needed that are functional and that O&M students can be taught to use to judge their safety effectively.
Functional Criteria For Assessing Risks
The following criteria, which are functional, quantifiable, and realistic, should be used to teach students to assess the risks of crossing streets. These criteria are that a street that has no traffic control could be considered safe for a person to cross only if
1. the traffic has gaps between the vehicles that are long enough to allow the person to cross safely and
2. the person can determine when the gaps will be long enough to cross the street. This criterion requires that the person must be able to detect the traffic well enough to have sufficient warning about whether a vehicle is coming, or judge the traffic's speed and distance well enough to know whether the gap between vehicles will be long enough to cross.
To illustrate how these criteria could be applied, assume that you rely on your hearing and are experienced or trained to know how long you need to cross streets of various widths. When you reach the street that you want to cross, you listen to the traffic and determine that the intersection has no traffic signal, that the street has no stop sign, and that the street is about two lanes wide (which indicates how much time is required to cross).
In the first example, you stand at the street corner for about 10 minutes, but the cars are all approaching too close to each other to allow you an opportunity to cross between them. Thus, the first criterion is not met (there are no gaps in traffic long enough to allow you to cross), and it would not be safe for you to cross.
In the second example, you come back at another time of day and notice that there is little traffic, that is, there are often long periods of complete silence, with no cars coming from either direction. These gaps in traffic certainly last sufficiently long to allow you time enough to cross, which satisfies the first criterion. However, you notice that even when it is quiet, most of the cars that come from your right cannot be heard until they are so close that you think you do not have enough warning of their approach. Hence, even though the first criterion has been met (there are gaps in the traffic that are long enough to allow you to cross), this situation is risky because the second criterion has not been met (during those gaps, you do not know whether a vehicle is coming that may reach you while you are crossing). If you crossed when you perceived a gap in the traffic, you would risk stepping out just when an undetected car was coming so close or so fast that the driver would have to slow down to avoid hitting you.
The first criterion (whether there are gaps long enough to cross safely) is straightforward and easy for a trained or experienced traveler to determine by noticing how wide the street is, how frequently vehicles approach, and whether there is enough time between vehicles to cross. The second criterion, however, is more complex and difficult to determine. It requires a person to judge whether he or she can detect the approaching vehicles with enough warning. Students can usually learn to make this determination if they are given feedback about the accuracy of their judgments. The importance of feedback is not surprising; receiving feedback is often effective for improving the accuracy of judgments. For example, in a study of a related skill (the ability to listen to an approaching car and judge when it will arrive), Rosenblum, Wuestefeld, and Saldana (1993) found that subjects who received feedback had greater accuracy than those who did not.
Teaching Students To Assess Risks
The author has developed strategies that provide this feedback effectively to O&M students.
Those who can see the traffic from afar can learn to judge its speed and distance well enough to know when it is sufficiently clear to cross by getting feedback from the Timing Method of Assessing the Speed and Distance of Vehicles, TMASD (Sauerburger, 1989, where it is called the Timing Method for Unlimited Detection; 1995).
When their ability to detect the traffic is limited (such as when they rely on hearing or impaired vision or when their view of the traffic is blocked with a hill or bend in the road), people can learn to judge whether they can detect the traffic sufficiently by getting feedback from the Timing Method for Assessing the Detection of Vehicles, or TMAD (Sauerburger, 1989, where it is called the Timing Method for Limited Detection; 1995).
Procedure To Assess And Develop Judgment
The process that the author uses to assess and, if necessary, help O&M students develop the ability to judge their safety for crossing streets with no traffic control is as follows:
1. Explain to the students that there are situations in which it is not possible to hear or see traffic well enough to know when to cross and that the purpose of this exercise is to assess and help them develop their ability to recognize these situations.
2. Go to an appropriate intersection at which one street has no traffic control. Ideal intersections have frequent but intermittent traffic, with many approaching vehicles, as well as many gaps in traffic.
3. If the street is not familiar to the students, have them determine its width either visually or by listening for cars passing on the other side of the street.
4. Ask the students to observe the traffic and determine if this is a situation in which they cannot see or hear the vehicles sufficiently to know when it is clear enough to cross.
5. When students who rely on hearing think that they can hear the traffic well enough to know when it is clear to cross, ask if they think they must have absolute quiet to hear the traffic sufficiently or if they can still hear the traffic well enough when there is background noise (such as distant lawnmowers or receding cars).
6. Use the TMAD to test their judgment and provide feedback.
7. Repeat this procedure of providing feedback in situations with a variety of conditions, until the students can judge whether or not they can determine when it is clear to cross in those conditions. To ensure that the students can recognize the two types of situations, give them experience in both situations. It is also best to sustain the conditions in each trial long enough to be tested, rather than to use conditions that alternate from good to poor, such as sporadic noise from construction or intermittent cloudiness.
Conclusion
Fifty years ago, at streets with no signal or stop sign, it was apparently safe to cross whenever it was quiet.
At that time, quiet was the only criterion needed to cross these streets safely.
Quiet is no longer a sufficient criterion.
O&M instructors need to add the criterion of the ability to hear or see the traffic sufficiently to know when there is a gap long enough to cross safely because with modern cars and today's streets, there are many situations in which it is not possible to hear approaching vehicles with enough warning.
O&M instructors need to teach students to recognize these situations, and one strategy they can use is to give the students feedback using the TMAD.
References
Allen, W., Courtney-Barbier, A., Griffin, A., Kern, T., & Shaw, C. (1997). Orientation and mobility teaching manual (2nd. ed.). New York: CIL Publications.
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.
Pogrund, R., Healy, G., Jones, K., Levack, N., Martin-Curry, S., Martinez, C., Marz, J., Roberson-Smith, B., & Urba, A. (1993). TAPS—An O&M curriculum for students with visual impairments. Austin: Texas School for the Blind and Visually Impaired.
Rosenblum, L., Wuestefeld, P., & Saldana, H. (1993). Auditory looming perception: Influences on anticipatory judgments. Perception, 22, 1467-1482.
Sauerburger, D. (1989). To cross or not to cross: Objective timing methods of assessing street crossings without traffic controls. RE:view, 21, 153-161.
Sauerburger, D. (1995). Safety awareness for crossing streets with no traffic control. Journal of Visual Impairment & Blindness, 89, 423-431.
Dona Sauerburger, M.A., orientation and mobility specialist, 1606 Huntcliff Way, Gambrills, MD 21054.
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