Research on problems of blind pedestrians
Although APS have been widely used in Japan and Sweden since the 1960s, the early development of APS in those countries was not, as far as these authors have been able to ascertain, based on research. Nor was there any research basis for the "cuckoo/cheep" APS that has been most commonly used in the U.S.
The first substantial research on APS appears to have been done in 1976 by Frank Hulscher, an electrical engineer with the Department of Motor Transport, New South Wales, Australia. Hulscher's research was the basis for the well developed, fully standardized, and highly successful APS system in use in Australia today.
Substantial research on APS in the U.S. began with a project undertaken by the San Diego Association of Governments in 1988. The results of this project were the basis for a policy of implementing standard signals at intersections in San Diego where a city access committee recommended them, following a systematic evaluation.
Since 1996, there has been a concerted research effort related to APS. Several research studies and surveys have documented problems of pedestrians who are blind or who have low vision at signalized intersections without APS. (Barlow, Bentzen, and Bond, 2005; Bentzen, Barlow and Bond, 2004; Bentzen, B.L., Barlow, J.M. & Franck, L. 2000; Carroll, J. & Bentzen, B.L. 1999; Murakami, Ishikawa, Ohkura, Sawai, Takato and Tauchi,1998, San Diego Association of Governments, 1988). Several studies in the U.S. have compared travel by blind pedestrians with and without APS. (Barlow, Bentzen, Bond and Gubbe, 2006; Crandall, Bentzen and Myers, 1998; Crandall, Brabyn, Bentzen and Myers, 1999; Crandall, Bentzen, Myers and Brabyn, 2001; Marston and Golledge, 2000; Uslan, Peck and Waddell, 1988; Williams, Van Houten, Ferraro, and Blasch, 2005). In these studies, some of the APS have been signals mounted on the pedestrian signal head, while others have been receiver-based systems, and others been pushbutton-integrated devices. Information in this section is drawn from these studies. A brief summary of each follows.
Surveys of blind pedestrians and orientation and mobility specialists
San Diego Association of Governments (1988; and Szato, Valerio, and Novak, 1991a, b, c, hereafter referred to collectively as San Diego research) surveyed 71 national, regional and local organizations representing and/or serving elderly persons and persons who were visually impaired to determine their involvement in installation of audible signals and the level of support for audible signals; 36 responses were received. A separate survey was also sent to members of California Association of Orientation and Mobility Specialists to gather information about their experience with audible signals. Surveys were mailed to 67 members and 27 responses were received.
In 1998, the American Council of the Blind (ACB) and the Association for Education and Rehabilitation of the Blind and Visually Impaired (AER) conducted similar surveys to determine problems experienced by blind pedestrians during street crossings. Problems with audible signals currently installed were also identified by the surveys.
- ACB survey (Carroll, J. & Bentzen, B.L. 1999, hereafter referred to as ACB survey) — surveys administered orally, in groups, to 158 pedestrians who are visually impaired
- AER survey (Bentzen, B.L., Barlow, J.M. & Franck, L. 2000, hereafter referred to as AER survey) — mailed to 1000 orientation and mobility specialists. 349 surveys returned.
Murakami, Ishikawa, Ohkura, Sawai, Takato and Tauchi (1998) conducted a survey of 50 blind pedestrians in Japan.
More details about the survey results, and references to studies which support the results, are provided in the section on crossing problems.
Uslan, Peck and Waddell (1988) compared crossings by 27 legally blind pedestrians at three intersections in Huntington Beach, California, having "bird call" signals and one control intersection without APS.
In research by The Smith-Kettlewell Eye Research Institute (Crandall, Bentzen and Myers, 1998, Crandall, Bentzen, Myers and Brabyn, 2001, Crandall, Brabyn, Bentzen and Myers, 1999, hereafter referred to collectively as SKERI research), 20 blind participants made a total of 80 crossings at 4 fixed-time signalized intersections in downtown San Francisco, both with and without Talking Signs®. Talking Signs is a receiver-based APS. Intersection signal phases were pretimed and pushbutton use was not required. There were nine measures, including measures of crossing timing (safety), orientation (precision), and independence.
Marston and Golledge (2000) compared crossings by blind participants with and without APS, using the receiver-based APS system, Talking Signs, in a study investigating the use of Talking Signs remote infrared audible signs for a number of transit tasks.
The effects of a pushbutton-integrated APS, a receiver-based APS manufactured by Relume, and typical visual pedestrian signals without APS on the street crossing behavior of 24 totally blind participants were compared by Williams, Van Houten, Ferraro, and Blasch (2005).
As part of a project on blind pedestrians at complex intersections, funded by the National Eye Institute, National Institutes of Health, a series of studies on crossings by blind pedestrians with and without APS is in progress in four cities, Portland, Oregon, Charlotte, Tucson, and Cambridge, Massachusetts. Objective data on measures of street crossing performance by sixteen participants who were blind was obtained at two complex, signalized intersections in each city. Measures were similar to those used in the SKERI research, including nine broad measures of crossing timing, orientation, and independence. Results from all four cities are not yet analyzed, but slightly different analyses have been reported in several articles. Results from pre-installation testing in two cities, Portland and Charlotte, are reported in Bentzen, Barlow and Bond (2004. hereafter referred to as NEI-2 cities) and Barlow, Bentzen, and Bond (2005, hereafter referred to as NEI-3 cities) reports on three cities, Portland, Charlotte and Cambridge. Barlow, Bentzen, Bond and Gubbe (2006, hereafter referred to as NEI Portland pre-post) compare results of testing with and without APS in one of these cities, Portland, Oregon.
Problems with specific tasks at signalized intersections by pedestrians who are blind or who have low vision
Locating the crosswalk
Pedestrians who are visually impaired use a variety of non-visual cues and strategies to locate crosswalks, none of which is absolutely reliable. Cues include proximity to the corner or to traffic on the street parallel to the pedestrian's direction of travel, location of curb ramps when present, location of idling cars on the street to be crossed, and presence of other pedestrians. When APS are present, they may also be used as an indication of the location of crosswalks.
ACB and AER surveys did not include specific questions about locating the crosswalk. 78% of individuals in the Japanese survey indicated that locating the crosswalk was difficult at intersections without APS.
In SKERI research, without APS, participants requested assistance in locating the crosswalk on 19% of street crossings. Participants were permitted to begin a crossing from any location that satisfied them, whether or not it was actually within the crosswalk lines. On 30% of trials, subjects who located the crosswalk independently began crossing from outside the crosswalk. (Participants were permitted to start crossing from any location so long as they were in no immediate danger.)
The NEI-3 cities results indicated that participants started from outside the crosswalk area on 28.3% of crossings and requested or required assistance locating the crosswalk on 15% of crossings.
Orientation (Aligning to cross and maintaining alignment while crossing)
Pedestrians who are visually impaired typically use a number of clues to help them align to face the direction of travel on the crosswalk before beginning to cross. These include vehicular sounds such as the direction of parallel traffic flow and the location of idling traffic on the street to be crossed. Another good cue, or strong predictor, of the direction of the destination corner is the direction pedestrians are traveling before they arrive at the starting corner. Additional cues that are useful in familiar locations are walls, fences, hedges, grasslines, and objects near the curb that have a straight surface that is either parallel or perpendicular to the direction of travel across the crosswalk. The direction of slope of the curb ramp, and the alignment of a truncated dome detectable warning near the bottom of the curb ramp are not reliable indicators of the direction of travel on the crosswalk, and when used either intentionally or inadvertently, may lead pedestrians who are visually impaired into the center of an intersection. Although there are numerous clues to the direction of travel on the crosswalk, none of them alone or in combination provide a definitive direction to pedestrians who are crossing at unfamiliar crosswalks.
Two clues used to help pedestrians who are blind maintain their alignment while crossing are the distance and direction of parallel traffic flow, and the location of idling vehicles on the perpendicular street. Even at familiar crossings these clues may not be sufficient to provide positive guidance to pedestrians who are blind as they are crossing a street.
In the AER survey, 97% of O&M specialists who responded indicated that their students had difficulty aligning to cross the street while 66% indicated that their students sometimes had difficulty knowing where the destination corner was. The most important reasons stated were that traffic was intermittent or the intersection was offset. In the ACB survey, 79% of respondents indicated that they sometimes have difficulty figuring out where the destination corner is.
Respondents to the Japanese survey indicated that "direction taking at the starting position" and "keeping direction while walking in the crosswalk" were a problem, even with APS.
The broadcast sound from speakers mounted on the pedestrian signal head has not seemed to provide usable directional information. ACB and AER surveys indicated that pedestrians who are blind are sometimes not able to localize the sound of an APS in order to use it for guidance across the street. ACB " 6%; AER " 39%. 85% of ACB respondents indicated that they were sometimes confused by unexpected features such as medians or islands while 64% of O&M respondents indicated that their students had difficulty with medians or islands.
In SKERI research, participants started crossing from an aligned position on 48% of crossings without use of APS, and completed their crossings within the crosswalk on 58% of crossings. In the NEI-3 cities research (without APS), participants started from an aligned position on 73.4% of crossings. Participants requested assistance or required intervention for safety while aligning to cross on 10% of crossings. Of participants who aligned independently, 58.4% completed their crossings within the crosswalk.
At 90–95% of signalized intersections today, signal timing is constantly adjusting to accomodate current vehicular and pedestrian traffic, and pedestrians are required to push a button to actuate a pedestrian timing to cross the street. Unless a pedestrian pushes the button, the WALK signal will not come on, and, when there is a green signal for parallel traffic, it is timed to accommodate vehicular traffic, not pedestrians. A pedestrian who does not push the button, and who crosses with the green signal for parallel traffic, may not have enough time to cross the street. The vehicular signal timing may be as much as 20 seocnds less than the pedestrian signal timing (Barlow and Franck, 2005). Therefore it is very important that pedestrians who are visually impaired use pushbuttons.
Blind pedestrians experience a number of problems with pushbuttons.
In the ACB and AER surveys, many respondents indicated that they or their students had difficulty with pushbuttons: ACB — 90%; AER — 94%. The following reasons were given.
- Users couldn't tell whether they needed to push a button.
- Users had difficulty locating the button.
- Users couldn't tell which crosswalk was actuated by the button.
- The pushbutton was so far from the crosswalk that users couldn't push the button and then return to the crosswalk and align to cross before the WALK interval began.
Uslan et al, (1998) also found that the major problems 27 legally blind participants had with "bird call" type APS, were in locating the pole and the pushbutton, and determining which pushbutton was for which crosswalk. Participants traveling with dog guides experienced the most difficulty locating the pole. Sometimes participants first located the incorrect button and subsequently located and pushed the correct button after waiting and listening through one or more cycles.
The San Diego research also identified problem with locating the pushbuttons and poles (Szeto et al. 1991a). Gallagher and Montes de Oca (1998) also noted this in research on vibrotactile-only APS.
In the NEI-2 cities results, at crossings where pushbutton-actuation was required, participants looked for, found, and pushed the button on only 16.3% of these crossings in Portland, and none (0%) of the crossings in Charlotte.
In research under NCHRP 3-62 (see NCHRP 3-62 Final Report, , and Bentzen, Scott and Barlow, in press), blind participants crossing at signalized intersections in Tucson, having APS, but without any instruction in use or purpose of the APS, failed to even search for pushbuttons on 29% of crossings.
Identifying the onset of the WALK interval
In the absence of an APS, pedestrians who are visually impaired rely on the stopping of perpendicular traffic followed by the onset of parallel traffic, to indicate the onset of the WALK interval. Pedestrians who do not quickly and accurately identify the onset of the WALK interval are likely to be delayed in starting to cross, may miss crossing on the first pedestrian phase, or may begin crossing when the WALK interval is not in effect. Complex geometry and intersection signalization make the use of traditional clues to the onset of the WALK interval unreliable.
Many respondents to the surveys indicated that they or their students sometimes had difficulty knowing when to begin crossing: ACB — 91%; AER — 98%. The following reasons were identified.
- The surge of traffic was masked by right turning traffic.
- Traffic flow was intermittent.
- The intersection was too noisy.
- The surge of traffic was too far away.
In the AER survey, 79% of respondents indicated that blind students sometimes had difficulty determining the onset of the WALK interval at intersections having exclusive pedestrian phasing.
In the Japanese survey, 46% of respondents stated that "to take a timing to start" was difficult without APS.
Uslan found that, at the control intersection without APS, which was considered the easiest to cross without APS, 4 out of 15 participants began crossing during DONT WALK.
In SKERI research on 24% of trials when APS information was not available, blind pedestrians requested assistance in knowing when to start crossing. On 34% of trials on which they independently initiated crossings, participants began crossing during the flashing or steady DONT WALK.
The NEI-3 cities research found that pedestrians who were blind independently began crossing during the WALK interval on only 48.6% of crossings and completed crossings after the onset of perpendicular traffic on 26.9% of crossings. The need for pushbutton-actuation of the WALK interval affected the likelihood that participants would begin crossing during the WALK interval. On the pedestrian-actuated crossings, participants began crossing during the WALK interval on only 19.5% of the crossings compared to 71.7% of crossings where the pedestrian phase was on recall (the pedestrian phase was included in every cycle).
Mean latency in beginning crossing (the time between onset of the WALK signal or near-side parallel traffic and the participant beginning to cross) was 6.41 seconds.
Problems with APS
The ACB and AER surveys were not limited to information about crossings that did not have APS; they had questions about APS volume, and about confusion of tones.
The 1998 ACB and AER surveys reported the experience of pedestrians with visual impairments in using APS that had "bird call" signals, bells and buzzers. There were problems both with APS being considered too quiet and too loud. 45% of participants in ACB survey considered signals to be too loud while 71% considered them too quiet. 24% of AER participants considered signals to be too loud, while 52% reported that APS were too quiet.
When APS are too loud, and are at intersections that are close together, the APS for one intersection may be heard from another, leading some pedestrians to incorrectly think they have the WALK interval. The surveys noted this problem: ACB " 19%; AER 25%.
In addition, complex phasing can contribute to problems with APS volume. Uslan et al. (1988) found that, at one intersection with split phase timing, where the bird call signals for parallel crosswalks had separate timing, three of 15 blind participants initiated their crossings with the signal for the parallel crosswalk, walking into the paths of left-turning vehicles.
Problems with APS — knowing which street has the WALK signal
Researchers particularly evaluated data on the AER and ACB surveys from blind pedestrians and O&M specialists from California, whose experience with APS is almost exclusively with "bird call" signals that are intended to provide unambiguous information regarding which street has the WALK interval. Many respondents indicated that they or their students sometimes did not know which crosswalk had the WALK interval (ACB " 68%; AER " 72%). Reasons were the following.
- Users forgot which signal was associated with which crossing direction;
- Users didn't know which direction they were traveling; and
- The intersection was not aligned with primary compass directions.
The San Diego researchalso indicated that blind pedestrians had difficulty remembering which sound was for which crossing direction.
Recent research in the NEI project and under NCHRP 3-62 addressed this issue. (See Chapter 3.)
Problems with APS — Confusion of tones with other sounds
Anecdotal evidence has existed for some time that some birds in the U.S. have calls that are like the cheep sound of some APS, and that other birds may mimic this sound. This has led to confusion between APS sounds, particularly the cheep sound, and the sounds of birds.
AER and ACB surveys confirmed that blind pedestrians really do confuse the sounds of birds with APS sounds. In the AER survey, 11% of respondents stated that their students had crossed the street with an actual bird and 10% stated that their students had not crossed because they thought the signal was a bird. Uslan et al. (1988) and the San Diego research also noted this as a problem.
To obtain a rough measure of the incidence of intersection crashes and near crashes for pedestrians who are visually impaired, the ACB survey asked respondents whether they had been struck by a car at an intersection, and whether they had had their long canes run over. In the ACB survey, 12 of 158 (8%) of respondents had been struck by a car at an intersection, and 45 (28%) had had their long canes run over.
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