Billie Louise Bentzen

Haptic cues for orientation and postural control in sighted and blind individuals

Haptic cues from fingertip contact with a stable surface attenuate body sway in subjects even when the contact forces are too small to provide physical support of the body. We investigated how haptic cues derived from contact of a cane with a stationary surface at low force levels aids postural control in sighted and congenitally blind individuals. Five sighted (eyes closed) and five congenitally blind subjects maintained a tandem Romberg stance in five conditions: (1) no cane; (2, 3) touch contact (<2 N of applied force) while holding the cane in a vertical or slanted orientation; and (4, 5) force contact (as much force as desired) in the vertical and slanted orientations. Touch contact of a cane at force levels below those necessary to provide significant physical stabilization was as effective as force contact in reducing postural sway in all subjects, compared to the no-cane condition. A slanted cane was far more effective in reducing postural sway than was a perpendicular cane. Cane use also decreased head displacement of sighted subjects far more than that of blind subjects. These results suggest that head movement control is linked to postural control through gaze stabilization reflexes in sighted subjects; such reflexes are absent in congenitally blind individuals and may account for their higher levels of head displacement.

New orientation and accessibility option for persons with visual impairment: transportation applications for remote infrared audible signage

Background:For a blind or visually impaired person, a vital prerequisite to accessing any feature of the built environment is being able to find this feature. Braille signs, even where available, do not replace the functions of print signage because they cannot be read from a distance. Remotely readable infrared signs utilise spoken infrared message transmissions to label key environmental features, so that a blind person with a suitable receiver can locate and identify them from a distance.

Directional guidance from audible pedestrian signals for street crossing

Typical audible pedestrian signals indicate when the pedestrian walk interval is in effect but provide little, or even misleading information for directional alignment. In three experiments, blind and blindfolded sighted adults crossed a simulated crossing with recorded traffic noise to approximate street sounds. This was done to investigate how characteristics of signal presentation affected usefulness of the auditory signal for guiding crossing behaviour. Crossing was more accurate when signals came only from the far end of the crossing rather than the typical practice of presenting signals simultaneously from both ends. Alternating the signal between ends of the crossing was not helpful. Also, the customary practice of signalling two parallel crossings at the same time drew participants somewhat toward the opposite crossing. Providing a locator tone at the end of the crossing during the pedestrian clearance interval improved crossing accuracy. These findings provide a basis for designing audible pedestrian signals to enhance directional guidance. The principal findings were the same for blind and sighted participants and applied across a range of specific signals (e.g. chirps, clicks, voices).

Wayfinding system for transportation services : Remote infrared audible signage for transit stations, surface transit, and intersections

People who are print-disabled, who are blind, or who have other visual impairments are restricted in their ability to participate in public life because of lack of labels and signs in the environment. Currently, persons with severe visual impairments often require extensive assistance from strangers to travel in unfamiliar areas. Many other types of disabilities can prevent people from reading print. In addition to people who are blind or who have low vision, there are many head-injured, autistic, and dyslexic (or even just educationally impaired) people, along with persons who have had a stroke, who are not able to assimilate printed language even though they can see the page. Many people can accept the information through speech—that is, having print read aloud to them. Some human factors evaluations of a signage system specifically developed to aid people who have visual impairments or a print-reading disability gain information that is available to sighted people through print are described in this paper. This remote, infrared audible signage system—Talking Signs—is composed of a small infrared transmitter that emits a repeating voice message over a directional light beam to a handheld receiver carried by the blind pedestrian. The infrared system greatly reduces the need for travelers to remember distances, directions, and turns, thereby enhancing independence and efficiency in travel. Results show that remote infrared audible signage provides effective wayfinding information for using transit stations, surface transit, and intersections, thereby enhancing independent use of public transit by people who have visual impairments or cognitive disabilities.

Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities

This report is intended to provide practitioners with useful information related to establishing safe crossings at roundabouts and channelized turn lanes for pedestrians with vision disabilities. The specific focus areas of the report provide guidance on: identifying under what conditions pedestrians with vision disabilities may experience problems with crossing performance; tying treatment solutions to specific crossing challenges faced by the visually impaired pedestrian population; conducting pedestrian/vehicle studies that help identify performance problems and appropriate treatment strategies; quantifying pedestrian accessibility at a particular crossing; presenting findings from selective field studies performed through this research; developing approaches for extending research findings to other locations; and discussing implications for the practitioner in terms of treatment selection and facility design. The results of this research will be useful to engineers, the accessibility community, policy makers, and the general public to aid in understanding the specific challenges experienced at these facilities by pedestrians with vision disabilities. It is only through the understanding of the components of the crossing task and the particular challenges involved that solutions can be developed, installed, and evaluated appropriately.

Accessible Pedestrian Signals at Complex Intersections: Effects on Blind Pedestrians

Pedestrians with vision impairments often have to cross streets at unfamiliar signalized intersections. The results are reported of research on crossings by blind pedestrians at complex intersections before and after the installation of accessible pedestrian signals (APS) and again following the installation of innovative device features. Objective data on measures of street crossing performance by 56 participants were obtained at four intersections, two each in Charlotte, North Carolina, and Portland, Oregon. The analysis includes broad measures of crossing timing, wayfinding, and independence. After APS installation, delay in starting to cross was reduced by approximately 2 s, and there was significant improvement in independently determining a safe time to cross, beginning to cross during the “Walk” signal, and completing crossings before the onset of perpendicular traffic. Some measures of wayfinding and related measures of independence also improved in Portland. Additional device features introduced after the first postinstallation testing session led to additional improvements in wayfinding during a second postinstallation test in Charlotte.

CHALLENGES OF UNFAMILIAR SIGNALIZED INTERSECTIONS FOR PEDESTRIANS WHO ARE BLIND: RESEARCH ON SAFETY

Pedestrians who are blind or visually impaired often travel in areas that are unfamiliar to them and cross at signalized intersections. Results are reported of testing street crossing by blind pedestrians at complex, unfamiliar signalized intersections without accessible pedestrian signals. There will be further reports on these results. The focus is on descriptive analysis of broad measures of safety, orientation, and need for assistance in crossing. Objective data on 12 measures of street-crossing performance were obtained at four intersections (two in each of two cities). In each city, 16 blind participants crossed at unfamiliar, complex signalized intersections without accessible pedestrian signals. Results confirm that blind pedestrians have considerable difficulty locating crosswalks, aligning to cross, determining the onset of the walk interval, maintaining a straight crossing path, and completing crossings before the onset of traffic perpendicular to their path of travel. Accessible pedestrian signals will be installed at the four intersections, and postinstallation data will be used to determine recommendations for accessible pedestrian signal characteristics and installation.

Determination of Pedestrian Push-Button Activation Duration at Typical Signalized Intersections

Recent advances in pedestrian push-button design, led by the development of accessible pedestrian signals (APSs), have created a new method of communicating traffic control information to pedestrians. Some APS devices have beaconing features or verbal (speech) message capabilities obtained by pressing and holding the pedestrian push button for approximately 3 s. Other features, such as the extension of the walk interval, may also be activated with an extended press of the push button. Recent research has suggested that 3 s may be excessive because it is hard for some users to hold the push button for this long. Additionally, most pedestrians may not hold the push button for this length of time. The problem lies in determining how long the APS push button should be pressed for a push-button information message or special accessibility features to be obtained. The primary objective of the research described in this paper was to develop a time distribution of typical pedestrian push-button activation durations. Data were obtained by attaching a voltage recorder to the pedestrian push-button circuit inside traffic signal controllers at eight locations in three cities in Wisconsin and Massachusetts. This device recorded the amount of time, to the nearest 1/100 of a second, that each pedestrian push button was pressed. A total of 1,439 push-button presses were recorded. The average push-button press duration was 0.2 s. More than 95% of all push-button presses recorded were less than 1.0 s. Only four push-button presses exceeded 3.0 s. The results show that the duration of an extended push-button press needed to obtain additional crossing information can be reduced to approximately 1 s without a significant number of false calls. A 1-s press will minimize the effort required for pedestrians to actuate special accessible features, while it will minimize unnecessary noise and vehicular traffic disruption.

Effectiveness of Audible and Tactile Heading Cues at Complex Intersections for Pedestrians Who Are Blind

This research extends the results of laboratory research on wayfinding at intersections for pedestrians who are blind. Standard accessible pedestrian signals (standard APS), a prototype beaconing APS, and a raised guide strip were evaluated for their ability to assist in establishing and maintaining a heading for street crossings. Experiments were conducted at large, complex signalized intersections in Alpharetta, Georgia; Austin, Texas; and Towson, Maryland. Both the guide strip and the beaconing APS resulted in more accurate street crossing performance than standard APS with respect to alignment (i.e., initial heading) accuracy, rates of being within the crosswalk, distance from the center of the crosswalk at various points during crossing, and the likelihood of being well outside the crosswalk [6 ft (2 m) or more]. For the most part, performance with the guide strip or the beaconing APS was equivalent. Limitations and additional concerns with respect to these two treatments are discussed.

Accessible Pedestrian Signals: Effect of Device Features

The U.S. Access Boards Draft Guidelines for Accessible Public Rights-of-Way recommends the use of push-button-integrated accessible pedestrian signals (APSs). This research compared the effect of specific features of push-button-integrated APSs on the ability of blind pedestrians to locate and correctly use push buttons and to cross accurately during the pedestrian phase. A rapid-tick walk signal promoted the fastest onset of crossing compared with speech messages and bird calls and is therefore the preferred signal. However, speech walk indications are needed where two APSs are mounted on the same pole. Although variations in the standard features made little difference to users who were thoroughly familiar with devices, empirical evidence from participants with less knowledge of the devices as well as subjective data lead to the recommendation that APS devices include a push-button locator tone, a rounded push button with an activation tone or message, a tactile arrow incorporated into the push button, responsiveness to ambient sound, and a push-button information message and beaconing in response to an extended button press.