Travel in adverse winter weather conditions by blind pedestrians: effect of cane tip design on travel on snow.
Having one's long cane get stuck may cause more frequent stops and starts, thereby increasing the time required to complete a given route. Such frequent stops and starts may also result in more steps being taken to cover a given distance which, in turn, may contribute to increased veering (Kallie, Schrater, & Legge, 2007). In addition, it appears that sticking can cause a traveler to veer from and can force the traveler's body to unintentionally turn from the intended line of travel (R. Savage, personal communication, April 2, 2015; M. Weessies, personal communication, April 2, 2015; S. Williams-Riseng, personal communication, December 10, 2014). Furthermore, cane sticking may cause frustration to the traveler by frequently disrupting a rhythmic cane swing (M. Ainsworth, personal communication, February 1, 2015; M. Jimenez, personal communication, February 1, 2015; N. Stanford, personal communication, January 31, 2015).
Only a handful of studies have examined the effect of cane tip design on the frequency of sticking. La Grow, Kjeldstad, and Lewandowski (1988) found no significant difference in the frequency of sticking among the pencil, marshmallow, and curved tips when participants traveled on a sidewalk in a residential neighborhood. However, Pietrowicz (1987) and Robertson (1987) reported significantly fewer instances of sticking when using the marshmallow tip than when using the pencil tip on a rural road and residential sidewalk, respectively. In addition, Wang (1991) found the ball tip to be more effective than the marshmallow or metal glide tip in reducing the incidents of sticking in a rural area. However, we found no published studies that experimentally examined the effect of cane tip design on cane sticking when traveling on a snow-covered surface. The purpose of the present study is to examine how different cane tip designs affect the travel performance of blind pedestrians on a snow-covered surface.
Study design and recruitment criteria
A repeated-measures design with Latin Square counter-balancing was used for the study. Recruitment criteria included legal blindness with no other disabilities, familiarity with basic cane techniques, regular travel in winter (even when the ground is covered with snow), and enough stamina to walk a few blocks without resting.
Participants used identical canes of different lengths (Ambutech UltraLite Graphite Rigid Cane) with four different cane tips perceived to be advantageous in reducing the incident of sticking (at least on dry surfaces): (1) metal glide tip (Ambutech MT 4070), (2) marshmallow roller tip (Ambutech MT 4090), (3) roller ball tip (Ambutech MT 4061), and (4) bundu basher tip (Bevria ES 4274) (see Figure 1). A participant's cane length was assigned based on height: vertical distance from the ground to two inches above the participant's xiphoid process, as described in La Grow and Long (2011).
Each participant signed the informed consent form approved by Western Michigan University's Human Subjects Institutional Review Board before participating in the study. Sleep shades (Mindfold Relaxation Mask) were worn by all participants during all trials (except for those with no light perception). A rectangular block in a residential neighborhood in Kalamazoo, Michigan, was selected for the study (see Figure 2). Upon receiving a signal from the experimenter, a participant walked from one end of the block to the other end (a straight path approximately 600 feet long) using the constant contact technique (or a modified constant contact technique as long as the same technique was used for all conditions). Although the participants were not given specific instructions on how much pressure to apply on the cane or how widely to swing the cane, they generally attempted to wield it in a manner that would minimize the frequency of sticking. Two independent raters tallied the frequency of cane sticking. For each sticking incident, they noted whether the cane got stuck on the snowy surface, snow bank, dry pavement, or grass. A cane tip was recorded to have stuck if the tip's forward movement was momentarily stopped by the irregularities of the walking surface, forcing the cane user to reposition the cane to resume his cane swing, regardless of whether he stopped his forward movement or not.
Experimenters also recorded the time it took the participant to walk the length of each block and how many times the participant veered off the sidewalk. If the participant failed to independently recover from veering within 30 seconds, one of the experimenters guided the participant back to the sidewalk so that he could resume his trial. Upon arriving at the end of the block, the participant was instructed to make a 180-degree turn and walk back to the starting point. Frequencies of sticking and veering, as well as travel time, were recorded for both the initial trip to the end of the block and the return trip to the starting point. Upon completion of all trials, participants were asked to rank the cane tips in the order of their preference for use on snow-covered surfaces.
Type of cane tip was the independent variable of the study. The dependent variables were (1) frequency of sticking, (2) frequency of veering, (3) time elapsed before arriving at a destination, and (4) preference rank.
Upon completion of descriptive statistical procedures, a repeated-measures analysis of variance (ANOVA) was used to examine the effect of cane tip type on travel performance. Repeated-measures t-tests were used for pair-wise post hoc comparisons. Friedman's ANOVA was used to compare preference rankings among the cane tips. A significance level of .05 was used for all statistical tests (two-tailed); Bonferroni correction was used for all pairwise post hoc tests. Statistical powers of the ANOVA tests were .94 when a large effect size (f = .4) was assumed, while the powers of post hoc f-tests were .48 with the assumption of a large effect size (d = .8) (Cohen, 1988; Erdfelder, Faul, & Buchner, 1996). All statistical analyses, except for power analyses (G*Power version 3.0.10), were conducted with SPSS version 20.
Demographic characteristics of the participants
Ten male and three female adults participated. Visual acuities ranged from no light perception to 20/400. Etiologies of participants' visual impairment included retinitis pigmentosa (n = 2), glaucoma (n = 2), diabetic retinopathy (n = 2), optic nerve atrophy (n = 2), Stargardt's (n = 1), and others (n = 4). Participants' ages ranged from 21 to 62 years (median age = 40 years). All participants either currently used or had used the long cane as their primary mobility device; 12 participants were current cane users and one was a dog guide user. The participants' cane use experience ranged from 5 years to 39 years (median = 12 years).
During all trials, snow banks--ranging from 6 inches to 14 inches high--were present on both sides of the sidewalk. The depth of snow on the sidewalk ranged from 1/2 inch to 6 inches. Such variations were present because the study was conducted on four different days. However, it should be noted that the snow conditions tended to be almost identical across the different cane tip conditions of a given participant. Seventy-five percent of the sticking incidents were caused by snow banks, 17% of them resulted from the snow-covered surface, and the remainder were from dry pavement and grass.
There was a statistically significant difference in frequency of sticking among the different cane tips, F(3, 36) = 21.28, p < .001 (see Figure 3). Post hoc analyses revealed that the sticking frequency for the metal glide tip (M = 28.3, SD = 16.6) was statistically significantly higher than that for the roller ball tip (M = 8.2, SD = 13.2,p < .001, d = 1.34), for the bundu basher tip (M = 10.7, SD = 8.8, p < .001, d = 1.33), and for the marshmallow roller tip (M = 17.4, SD = 14.1, p = .001, d = .71). In addition, there was a statistically significant difference in sticking frequency between the marshmallow roller tip and the roller ball tip, p = .003, d = .67.
Elapsed travel time and veering
There was no statistically significant difference in travel time (time elapsed before arriving at a destination) among the different cane tips, F(3, 36) = 2.03, p = .127 (see Figure 4). Similarly, there was no statistically significant difference among the cane tips in veering frequency, F(3, 36) = .25, p = .864.
There was a statistically significant difference in preference ranking (1 being the highest and 4 being the lowest) among the cane tips, [chi square] = 9.65, p = .022. Participants ranked the roller ball tip as the preferred cane tip for use on a snow-covered surface (M = 1.9, SD = 1.0), which was followed by the marshmallow roller tip (M = 2.2, SD = .8), the bundu basher tip (M = 2.5, SD = 1.0), and the metal glide tip (M = 3.4, SD = 1.2).
Interpretation and practical implications In this study, we found that cane users experienced significantly more sticking on snow-covered surfaces when using the metal glide tip than when they used the roller ball, bundu basher, or marshmallow roller tip. The roller ball tip was ranked as the preferred cane tip for travel on snow, while the metal glide tip was the least desired.
Our findings on frequency of sticking with different cane tips are generally consistent with the findings of similar previous studies conducted on dry walking surfaces (Robertson, 1987; Wang, 1991). Cane tip shape appears to have contributed to differences in sticking frequency. For example, the metal glide tip, being the smallest and most sharply angled among the four cane tips, tended to get stuck on snow more often than more rounded and larger cane tips.
It was somewhat surprising to find that, despite the significant difference in sticking frequency, there was little difference in travel time among different cane tips. This appears to have resulted from the fact that most of the participants did not stop their forward movement even when their cane tip was stuck on the surface, partly because they knew it was a safe environment (no obstacles) and they therefore didn't think it was necessary to break their stride even when their cane was momentarily stuck. In addition, similar veering frequency among the different cane tips might have resulted from the fact that there were grass lines (snow banks) on both sides of the sidewalk and the driveways the participants had to cross were rather narrow (9-12 feet wide), which limited the chances for veering.
Differences in sticking frequency among the cane tips observed in this study appear to be large enough to be practically significant. For example, a difference of 20 incidents of sticking between the metal glide tip and the roller ball tip (28 vs. 8) during a 400-yard walk appears to be a substantial difference that has practical implications for the cane users; frequent cane sticking may frustrate the traveler, thus increasing stress level during travel. No significant difference in travel time among the cane tips was observed in this study, partly due to the fact that most of the participants chose not to stop their forward movement even when their cane tip was stuck. However, this is not a safe practice when traveling in an unfamiliar environment. In an unfamiliar environment, cane users tend to stop or pause their forward movement momentarily when their cane gets stuck on the walking surface (while they bring their cane back to rhythmic swinging) in fear of colliding with unexpected obstacles or hazards. In such situations, a higher frequency of sticking may lead to longer travel time as well.
Limitations and recommendations
One of the limitations of the study is related to the change in depth and consistency of snow conditions from one condition to the next-resulting from snow plowing by the residents. However, noticeable snow plowing during the trials occurred only for one of the participants. Another limitation results from the small convenience sample, which limits the generalizability of the study findings. Future studies may be conducted at a site where no individual plowing occurs (such as an unused sidewalk on campus) to keep snow conditions virtually identical across different cane tip conditions for all participants. They might also include an investigation of how cane sticking affects veering in a more open space (such as a parking lot). In addition, conducting a similar study with obstacles randomly placed in one's travel path may be helpful in understanding how sticking affects cane users' ability to detect obstacles. Such study would also shed more light on how cane sticking affects travel time in an environment with which the traveler is not familiar. Furthermore, investigation of how different cane techniques and different cane-holding methods affect cane sticking might be useful.
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Dae Shik Kim, Ph.D., COMS, CLVT, professor, Department of Blindness and Low Vision Studies, Western Michigan University, 1903 West Michigan Avenue, Kalamazoo, MI 49008; e-mail: <firstname.lastname@example.org>. Robert Wall Emerson, Ph.D., consulting editor for research, Journal of Visual Impairment & Blindness, and professor, Department of Blindness and Low Vision Studies, Western Michigan University; e-mail: <email@example.com>. Eleni Gaves, B.S., graduate student, Department of Blindness and Low Vision Studies, Western Michigan University; e-mail: <firstname.lastname@example.org>.
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|Title Annotation:||Research Report|
|Author:||Kim, Dae Shik; Emerson, Robert Wall; Gaves, Eleni|
|Publication:||Journal of Visual Impairment & Blindness|
|Date:||Jan 1, 2016|
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