Home Modification Resources

An Analysis of the Effects of Ramp Slope on People with Mobility Impairments

Jon A. Sanford, M.Arch., Molly Follette Story, M.S., and Michael L. Jones, Ph.D.

The Center for Universal Design, School of Design, North Carolina State University, Raleigh, North Carolina

A study was conducted to evaluate the usability of the range of ramp slopes allowed under the current ADA accessibility guidelines. One hundred seventy-one subjects of all ages and using different types of mobility aids traversed a 30-foot ramp varying in slope from 1:8 to 1:20. Data were recorded for pulse rate, energy expenditure, rate of travel, distance traveled, and the location of rest stops. Findings show that among all subjects only a few manual wheelchair users had difficulty traversing all 30 feet in ascent, even on slopes as steep as 1:8. Based on these results, changes to the technical requirements for ramp slope and length cannot be recommended at this time.

Key Words: Ramp slope--Accessibility--ADA--Mobility Impairment.

Section 502 of the Rehabilitation Act of 1973 established the Architectural and Transportation Barriers Compliance Board (Access Board) as an independent federal agency to ensure compliance with standards issued under the Architectural Barriers Act. The 1978 amendments to the Rehabilitation Act of 1973 gave the Access Board the responsibility to establish Minimum Guidelines and Requirements for Accessible Design (MGRAD) to ensure that buildings designed, constructed, or altered by or on behalf of the federal government were accessible to people with disabilities. Subsequently, with the passage of the Americans with Disabilities Act (ADA) in 1990, the Access Board also was mandated to issue accessibility guidelines that could be used by the Departments of Justice and Transportation to establish accessibility standards in places of public accommodation, commercial facilities, and transit vehicles and facilities.

Section 4.8 of the proposed Americans with Disabilities Act Accessibility Guidelines (ADAAG) specified that ramp slopes not exceed a ratio of 1 inch in vertical rise to 12 inches of horizontal run for a maximum rise of 30 inches (i.e., a maximum distance of 30 feet between level landings for a 1: 12 slope). Although this specification was based on existing MGRAD and ANSI A117.1 Accessibility Standards, there was growing concern that a 1:12 slope was too steep. In fact, public response to the proposed guideline was such that one third of the respondents recommended that the maximum slope be reduced (Access Board, 1993).

In response to the concern regarding the technical requirements for ramps, the Access Board contracted with The Center for Universal Design, North Carolina State University, to undertake the study of ramp slope and length reported in this paper. The purpose of this project was to determine whether existing technical requirements for ramps (1:12 maximum slope over a 30-foot length and a 1:8 maximum slope for a 6-inch rise) were appropriate for people of all ages who use a variety of mobility aids. As a result, the study was limited to evaluating the existing requirements for ramp slope and length. Based on the results of the study, recommendations for changes to ADAAG technical requirements for the maximum slope and length of ramps were made, as well as recommendations for areas of future research.

BACKGROUND

Recent legislation such as the Rehabilitation Act of 1973, the Fair Housing Amendments Act of 1988, and the ADA suggest that there will be an increased reliance on ramps for entry to and egress from public facilities. At the same time, the validity of existing code and standard requirements for ramps has been questioned with increasing frequency, particularly for older individuals. Czaja (1984), Faletti (1984), Sanford & Megrew (1995), Steinfeld & Shea (1993), and others have argued that accessibility standards are typically based on the capabilities of young people with singular disabilities, and as such are inappropriate for the increasing population of older people who have a range of mobility and sensory limitations as well as reduced strength and stamina.

Prior studies have focused on human performance on ramps; however, recommended gradients from these studies vary widely. For example, both Elmer (1957) and Canale et al. (1991) recommended fairly steep ramp slopes (up to 1:6 and 1:6.7, respectively), whereas Steinfeld, Shroeder, & Bishop (1979) concluded that ramp slope should vary between 1: 16 and 1: 20. Discrepancies such as these are likely due to several factors, including use of different test populations and variation in performance measures used. For a variety of reasons (e.g., samples of convenience), most studies have used different subject populations that were dissimilar in age and level of functioning. For example, Elmer (1957) and Canale et al. (1991) used younger samples with good upper-body strength who were able to propel their own wheelchairs fairly easily. In contrast, Steinfeld, Schroeder, & Bishop (1979) included a large sample of older people and people with more limited functioning, and Lehmann et al. (1974) tested persons with C5-C8 quadriplegia. As a result, differences in observed performance seem to be associated with the impact of ramp characteristics on the particular population evaluated rather than on ramp slope alone. Critical factors differentiating these populations include degree of mobility (i.e., nonambulatory individuals who use self-propelled, attendant-propelled, or powered wheelchairs or ambulatory individuals who walk with difficulty and/or use assistive walking devices), speed, and stamina.

Performance measures and procedures also varied widely across studies. Studies have included a number of objective performance measures such as energy consumption (Findley & Agre, 1988; Voight & Bahn, 1969), time required to traverse a ramp, maximum distance attained, distance between stops, number of strokes made on the wheelchair rim (for independent wheelchair users), and number of steps taken (for attendant-propelled wheelchair users and those using assistive walking devices), as well as subjective measures such as asking participants to stop when they needed to rest (Elmer, 1957; van der Voordt, 1981; Walter, 197 1). In addition, gradients and length of ramps tested have been inconsistent. In general, studies have evaluated gradients ranging from 1:6 to 1:20. However, individual studies have evaluated only one or a limited number of slopes. Ramp lengths have also varied in a similar manner. For example, Lehmann et al. (1974), as well as Walter (1971), tested subjects on 10-foot ramps. However, Walter (1971) used 20-foot ramps, and Steinfeld, Schroeder, & Bishop (1979) used 40-foot ramps. In contrast, van der Voordt (1981) evaluated longer ramps with rest landings every 30 or 45 feet, whereas Templer, Wineman, & Zimring (1982) focused on even longer ramps without rest areas.

Due to the differences in past research, it is not surprising that there is a lack of consensus among researchers regarding optimal ramp slope and length. Moreover, the lack of comparable procedures, measures, and samples makes it difficult to generalize recommendations from the research findings. These discrepancies suggest that research on the impact of ramp slope for a wide range of ages and types of mobility limitations is warranted. In fact, the significant changes in demographics over the past 2 decades and the projected increase in the number of older people and people with disabilities over the next 50 years (Bureau of the Census, 1983, 1992; Chirikos, 1986; Colvez and Blanchet, 1981; Kunkel and Applebaum, 1992; LaPlante, Hendershot, & Moss, 1992; Zola, 1993) suggest that a reevaluation of the current ADA requirements for the design of ramps for their usability by current and anticipated populations is not only appropriate, but perhaps long overdue.

METHODOLOGY

Sample

Sampling Frame

Based on an analysis of population trends (Jones & Sanford, 1996), a sampling frame was developed to accurately reflect the population profile of people with mobility impairments in the U.S. today (Table 1). The anticipated sample of 192 was based on four subjects in each of the 48 cells derived from the six age groupings and eight categories of people with mobility impairments used. The sample was distributed by age and gender among the seven categories of assistive devices used for mobility and an eighth category of individuals with mobility impairments who do not use assistive mobility aids.

Subject Recruitment

Several methods were used to solicit subjects to take part in the study. First, individuals listed in The Center for Universal Design's Design Advisory Network (DAN) database who matched the sampling frame were identified and contacted by telephone. Second, telephone inquiries were made to local disability support groups and advocacy groups, as well as to rehabilitation facilities and agencies, to obtain their assistance in identifying subjects. Flyers were delivered to local libraries, churches, group homes and care facilities, senior citizens' centers, and orthotics shops. Ads were run in the Raleigh newspaper and, because a large number of older adults were needed, in a local publication targeted to seniors. Center staff made presentations at several meetings of senior citizens and other local disability support groups.

Test Sample

The test sample was selected to match the general population of mobility aid users. A total of 171 subjects (Table 2) representing 43 of the 51 cells in the sampling frame participated. The ratio of males (41.5%) to females (58.5%) remained true to the sampling frame (41.7 to 58.3%). Seven of the eight cells for whom no participants were found were single-representative cells, the eighth was a two-person cell. Older participants over 75 years of age accounted for the largest number (10) of missing subjects. However, this age group was the largest in the sampling frame. As a result, 85.7% of the targeted number of subjects participated. By mobility category, subjects who used canes or crutches had the largest shortfall (14) from the sampling frame. However, this subgroup accounted for the largest single cell mobility in the sampling frame (99). As a result, 85.9% of the targeted sample was tested. Table 3 shows the frequency of test trials by subject and type of mobility aid.

Test Apparatus

A 30-foot aluminum ramp consisting of three, 3-foot-wide by 10-foot-long sections with a triple row of tubular aluminum side railings (at 8, 21.5, and 34 inches above the ramp surface) was constructed (Fig. 1). A 5-foot landing created a transition from the floor to the ramp. The top end of the ramp was connected to a 5-foot by 8-foot aluminum terminal landing fitted with a triple row of tubular aluminum side railings. The ramp was adjustable to seven calibrated slopes: level, 1:20, 1:16, 1:14, 1: 12, 1:10 and 1:8 (Fig. 2). Two manually operated winches adjusted the height of the ramp. The terminal landing height was controlled by two additional manually operated winches. The ramp surface was marked with 1/2-inch vinyl tape across its entire width at 6-inch intervals and labeled in 1-foot increments, from "O" to "30," along either side in order to facilitate data collection.

A surface electrode (Nellcor model RS 10 reflectance oxisensor) held in place on each subject's forehead with a cotton elastic headband was used to monitor pulse rate and oxygen saturation level throughout each trial. Both measures were electronically collected using a Nellcor model N20, self-calibrating, portable pulse oximeter that is widely used to determine pulse and oxygen saturation.

Test Site

The test site was the lobby space of a former hotel that had been purchased by the University. This space was ideal, as a minimum floor space of 20 feet by 50 feet and a minimum vertical clearance of 12 feet were necessary to accommodate the test ramp. In addition, the site and restroom facilities were accessible. Finally, the indoor site afforded ambient conditions that were safe and comfortable for subjects.

Test Procedures

At a minimum, three staff were present for each trial. One was responsible for videotaping the session; one served as a spotter, accompanying the subject on the ramp and monitoring physical exertion; and one recorded data. All staff members involved in testing were certified by the American Red Cross in basic first aid and CPR. Prior to initiating the test trials, a signed consent form was obtained; test procedures, equipment, and safety issues were explained; surface electrodes were positioned on the subject's forehead; and the subject was escorted to the bottom landing. Two baseline trials (forward and return) were always conducted first, with the ramp in the level position. Following the two baseline trials, subjects were asked to ascend and descend six additional slopes (1:8, 1:10, 1:12, 1:14, 1:16, and 1:20). Thus, each subject undertook a total of 14 trials. In order to minimize the effects of fatigue on subjects' ability to use the ramp, the six inclines were presented in a random order determined by rolling a die prior to the session.

Prior to each trial, subjects were asked if they would attempt to traverse that particular incline unassisted in the course of everyday travel. Participants were then instructed to traverse the ramp at a comfortable pace, pausing as needed and simulating the way they would typically use a ramp. Pulse and oxygen saturation levels were monitored continuously throughout the trial to alert the spotter should the subject become over-exerted.1 The participant then rated the ramp difficulty. The spotter remained with the subject on the top or bottom landing, as necessary, until pulse and oxygen levels stabilized to within 3% of resting levels. Upon completion of all trials, participants were asked to complete a participant evaluation form to provide feedback on their impressions of the testing procedures. Participants were asked to judge how closely the test procedures matched their real-life situations with ramps in everyday environments. Trial data were recorded on preprogrammed Newton Message Pad 110s. At the end of each day of testing, data were uploaded from the Newtons to a Macintosh computer and onto a database application.

Data Collection

Data for seven dependent variables were collected for each ramp trial.

1) Total Distance was a measure of the farthest distance traveled on the ramp. Minimum and maximum distances were 0 and 30 feet, respectively. Total distance was defined as the last 6-inch interval crossed by the back of a subject's trailing foot or the rearmost wheel of the wheelchair or scooter. Total distance was recorded when either the entire ramp had been traversed or forward motion on the ramp had ceased due to 1) a subject's inability to continue, 2) the spotter terminating the trial (e.g., because of escalated pulse rate or reduced oxygen saturation level), or 3) a subject ceasing forward motion for more than 5 seconds for the third time during the trial.

2) Total Time was a measure of the elapsed time from the time the starting point was crossed to the stopping point. Timing began when the back of the subject's trailing foot or the rearmost wheel of a wheelchair/scooter crossed the starting line. Timing was discontinued when the subject either traversed the entire ramp or had ceased forward motion (when neither foot or rearmost wheel was moving in the direction of travel for at least 5 seconds).

3) Location and Duration of Rest Stops were recorded each time a subject paused on the ramp for at least 5 seconds. The location was determined as the last 6-inch interval crossed by the subject's trailing foot or the rearmost wheel of his/her wheelchair or scooter. The duration was defined as the elapsed time from the instant forward motion ceased until forward motion was resumed. Subjects were allowed to take up to two 15-minute rest stops during a trial.

4) Pulse Rate and Oxygen Saturation Level were recorded throughout each trial using a Nellcor N20 portable pulse oximeter that was attached to a surface electrode on the subject's forehead and held in place with a cotton elastic headband. Initial readings of pulse and blood oxygen saturation were recorded prior to the first trial. Changes in these two measures were recorded at the end of each trial to document exertion due to the trial.

5) Difficulty Levels and Problems Encountered, including ability to control speed of ascent and descent as well as railing usage (one or both sides), were noted. In addition, types and locations of problems, including stumbling, slipping, tipping of wheelchairs, collisions, faltering due to too little speed on ascents, hesitant descents, unusual directions of travel, and meandering, were recorded.

6) Type of Assistance given to a subject (e.g., physical support or preventing loss of control), as well as location on the ramp, was recorded.

7) Subjective Ratings of Trial Difficulty were recorded on a 10-point graphic scale after each trial. The scale was anchored by five faces above the scale, registering expressions ranging from satisfaction to frustration. Subjects were asked to choose the face or number that most accurately represented how difficult they perceived that trial.

RESULTS

Interrater Reliability

When possible, two observers independently recorded performance in test trials. Based on staff availability, 68% of the trials were able to be monitored by two observers. If the total time taken to travel the ramp or the length of a rest stop for any trial differed by more than 5% between the two observers or if the maximum distance traveled or the location of any rest stop differed by more than 6 inches, the videotape of that trial was reviewed by the two observers in order to reconcile the error. This procedure resulted in a 100% interrater reliability.

Distance Traveled

The sample as a whole had little trouble completing each of the trials in ascent and had even less difficulty in descent. In fact, so few trials (only 3 out of 1,178) were not completed in descent that the data are not significantly different from chance. Moreover, the incomplete trials occurred at three different slopes, including one subject who did not walk the return 30 feet at zero (0) slope.

The sample as a whole also completed the vast majority of trials (1,162 out of 1,179) in ascent. However, despite the 98.6% completion rate for all trials, the distribution of the incomplete trials fell almost exclusively within the manual wheelchair subsample - 15 of the 17 (88.2%) were by subjects who used manual wheelchairs and the remaining two (11.8%) were by those who used canes. However, these figures represented only 10.8% and 0.4% of all trials involving people who used wheelchairs and those who used canes, respectively.

When ascent was analyzed by slope and mobility category, the two trials in which cane users were unable to reach the top of the ramp occurred on the two shallowest slopes, although the subjects were able to walk all 30 feet at each of the other slopes. As a result, the failures were probably attributable to overall fatigue due to testing rather than the subjects' inability to traverse a given slope.

In contrast, for subjects who used wheelchairs, the three steepest slopes accounted for 80% of the incomplete trials. Moreover, the same five subjects were responsible for all of the incomplete trials (Table 4). One subject failed to complete all six slopes, and two additional subjects failed to complete the three slopes steeper than 1: 14. Therefore, of the 20 subjects in manual wheelchairs, 95% were able to complete slopes between 1:20 and 1: 14. Only 85% were able to traverse 30 feet at a slope of 1:12, 80% were able to traverse 30 feet at 1:10, and 75% were able to traverse 30 feet at 1:8. Interestingly, the five subjects who failed to ascend all 30 feet were all women, four of whom were over 65 years of age. This finding differed from the sample as a whole in which age by itself was neither a significant factor in determining success nor mean distance traveled. In fact, the findings indicate that there were no significant differences within age groups in mean distance traveled across any of the six slopes, nor were there significant differences across age groups (Table 5).

Rest Stops

Of the 1,179 ascent trials, only 24 (2.0%) involved the participant stopping to rest, although subjects who did not complete a trial stopped on the ramp more often and at shorter distances than those who completed the trials. This is evidenced by the greater mean number of rest stops for those who did not traverse all 30 feet (1.24 per trial) compared to those who were able to traverse all 30 feet (0.01). The mean distance to rest stops for the incomplete group was also less (7.44 feet for rest stop 1 and 12.83 feet for rest stop 2) than for subjects who traversed all 30 feet (16.98 and 25.75 feet, respectively). However, when number, distance, and duration of stops were analyzed by slope, there was no significant effect of slope on these measures. Although the number of subjects who stopped once increased between slopes of 1:20 and 1:8, this increase was small (1.2 to 5.2%) and represented a difference of only seven people. Moreover, of the nine that stopped on the 1:8 slope, seven (77.8%) continued to the end of the ramp.

Speed

The overall trend, with few exceptions, was that speed of ascent decreased as slope increased from 1:20 to 1:8 (Fig. 3). Although the decrease in speed within each mobility aid subgroup was generally not significant, there was a downward trend. The data also reveal that subjects with different mobility aids traveled at different speeds, regardless of slope. Although increases in ramp gradient had a proportionately similar effect on speed for all ambulatory and "other" subjects, it had a dramatic effect on speed of wheelchair users. Interestingly, however, this effect was fairly equally evident across all slopes, not just the steeper gradients. The only significant difference noted was the 50% reduction in speed between the level (O slope) and a 1:8 slope within the manual wheelchair group.

Pulse

Across mobility categories, there were no significant differences at zero slope, indicating that pulse rates, as would be expected, were similar for all subgroups on a level surface. However, subjects who used wheelchairs had significantly higher changes in pulse rate at each gradient, indicating that slope had a greater effect on people who used wheelchairs (Fig. 4). When pulse was examined within mobility aid category, rate remained fairly stable for the two ambulatory subgroups that used mobility aids (canes and walkers). In contrast, there were significantly higher and increasing pulse rates among the wheelchair and brace subgroups. For subjects who used braces, there were significant increases in pulse rates between zero and the two steepest slopes, although there were no differences between any other gradients. Among subjects who used manual wheelchairs, there was a significant increase between 0 and 1: 14 slope. At 1: 14, the change in pulse rate reached a plateau, with no significant differences among slopes of 1:14, 1:12, and 1:10. At 1:8, pulse rates increased again.

Oxygen Saturation

Mean levels of oxygen saturation ranged from 98.24 to 99.77%. Not only were there no statistical differences in these measures, but the mean levels were so high (exertion is only evident when saturation begins to fall below 90%) that exertion was not evident in any of the mobility subgroups. This suggests that 30 feet at any of the gradients tested may not have been a strenuous task for any of the mobility subsamples.

Subjective Responses

Although mean difficulty ratings in ascent increased significantly within each mobility aid subgroup as slope increased, only two mobility subgroups-manual wheelchairs (5.84 on 1:10 and 6.73 on 1:8) and walkers (5.16 on 1:8) had mean difficulty ratings above 5 on a 10-point scale on any slope. It is also interesting to note that these two subgroups rated each level more difficult than the other mobility aid subgroups. In contrast, in descent, the differences among subgroups were less evident, as no mean rating exceeded 4.0 for any slope except on the steepest slope by those who used walkers (mean = 5.58). When subjects were asked if they would try to ascend the ramp alone, five (two with braces, one cane user, two with walkers) responded that they would not try a slope of 1:8 and one (with a walker) would not try a slope of 1:10. In descent, nine subjects reported that they would not try slopes ranging from 1: 14 to 1:8, although seven of the nine involved the two steepest slopes. These subjects included individuals who used walkers (one at 1: 12, two at 1:10, and three at 1:8), canes (one at 1:8), and braces (one at 1:8). One person in a manual wheelchair would not have attempted a slope of 1: 14.

DISCUSSION

Although not particularly surprising, the data indicate that none of the factors of interest in this study-slope, mobility aid, gender, and age-individually had much of a bearing on subjects'ability to travel or amount of effort expended in descending a 30-foot-long ramp. However, the interaction among all four factors did have an impact on ramp use in ascent.

Distance traveled is perhaps the most notable evidence suggesting that increasing slope impacts performance of older wheelchair users, particularly women. Of the 151 ambulatory and "other" subjects, only two cases (both involving cane users at shallow gradients) resulted in subjects terminating prior to reaching the top of the ramp. Similar percentages of ambulatory participants using mobility aids who were able to traverse ramps of varying slopes and distances have been reported in other studies (c.f., Steinfeld, Schroeder, & Bishop, 1979; van der Voordt, 1981; Walter, 1971).

In contrast, data from this research indicate that only 85% of the participants who used manual wheelchairs were able to traverse 30 feet at a slope of 1:12, 80% were able to traverse 30 feet at 1:10, and 75% were able to traverse 30 feet at 1:8. Although these findings are consistent with some previous research, the varying slopes and lengths of ramps used in previous research makes direct comparisons difficult. For example, Templer, Wineman, & Zimring (1982) also found that 80% of manual wheelchair users could traverse a ramp with a slope of 1:10.1. More recently, Sweeney et al. (1989) reported that 88% of the subjects who participated in their study were able to traverse short gradients between 1: 12 and 1: 7. In contrast, other studies have reported greater numbers of self-propelled manual wheelchair users having difficulty on gradients of 1:12 and steeper. For example, Steinfeld, Schroeder, & Bishop (1979) found that almost 50% of their subjects were unable to ascend a 40-foot ramp with a 1: 12 slope and only 30% of the manual wheelchair users could complete a distance of 5 feet at this gradient.

Thus, a 1: 12 slope at distances of 30 feet may be too difficult for certain segments of the population that use manual wheelchairs, most notably those who are older and female. This is further evidenced by the increased number of rest stops required by manual wheelchair users within the 30-foot distance in comparison to the rest of the sample. However, subject recruitment efforts for this study suggest that, whereas the population of older women who use manual wheelchairs is relatively large, the number who independently travel outdoors may be relatively small. This subsample tended to use manual wheelchairs to get around the home when they tired, but relied on someone else to push them when they were outside their homes. This seems to be the result of their frailty and inability to propel themselves over the distances required rather than the slope of the surfaces. As a result, the actual impact of ramp slope on independent mobility of this population may be minimal. Further research should be conducted to characterize the general mobility of older women and to determine the extent to which this population is likely to engage in independent outdoor mobility such that the impact of ramp slope can be assessed.

The data also indicate that only people who use manual wheelchairs experienced significant decreases in speed due to slope. These subjects, unlike the rest of the sample, also experienced a significant increase in pulse rate, although it was only between the baseline and a slope of 1:14. In contrast, the oxygen saturation data, like that from previous studies (Findley and Agre, 1988), indicate that wheelchair users expend only slightly more energy than ambulatory subjects in traversing an incline, although none of the subgroups exhibited significant cardiovascular exertion. It is likely that other factors, such as muscle fatigue due to distance or speed, may have a greater impact on exertion than does slope.

People who used walkers, as a group, perceived that they had more difficulty in both ascent and descent, particularly on steeper slopes, than did individuals who used other mobility aids. Future research might investigate the impact of ascending as well as descending slope on the design of walkers in order to develop alternative designs that will facilitate traversing ramps.

Finally, it should be noted that ADAAG currently does not limit overall ramp length, the number of landings, or the ramp configuration (i.e., number of turns). As a consequence, this project did not address these issues. However, it is reasonable to assume that these factors could cause additional strain that might impact the strength and stamina of people with disabilities. As a result, 1: 12 might be too steep for longer, winding ramps. To date, only one study (Templer, Wineman, & Zimring, 1984) has examined long ramps. Although the ramps studied varied in length, all were straight. As a result, an investigation of the impact of long ramps of varying slopes, lengths, and configurations is warranted.

In summary, the data suggest that a 30-foot ramp at a slope of 1: 12 or higher presents a barrier for some manual wheelchair users but not for people who use other types of mobility aids. However, with the exception of older females, whose tendency to engage in independent outdoor mobility is questionable, a surprisingly high percentage of manual wheelchair users were able to traverse fairly steep ramps (75% at 1:8) and did so without expending energy at risky levels. This suggests that perhaps even older individuals could traverse ramps steeper than 1:12 if there were shorter distances between level landings. Such an assertion is supported by others (Canale et al., 1991; Cappozzo et al., 1991; Sweeney et al., 1989; Sweeney & Clark, 1991), who have suggested that people who use wheelchairs may be more successful at ascending short ramps of steeper gradients than long ramps of slopes 1:12 or less. However, despite acceptable performance in ascending steeper inclines, data from this as well as previous studies (van der Voordt, 1981; Walter, 1971) suggest that people who use wheelchairs fear tipping over backwards on slopes greater than 1:12. As a result, steeper gradients may be less desirable for this population.

IMPLICATIONS

Based on the performance of the entire sample, it could be argued that the maximum allowable slope of ramps could be increased, even if for distances shorter than 30 feet. Alternatively, it could be argued that the maximum distance allowable between landings for 1:12 ramps could be increased beyond 30 feet. In fact, these conclusions are bolstered by anecdotal evidence that suggests that those manual wheelchair users who were most impacted by ramp slope-women over 65may be too frail to routinely travel outdoors independently even on level surfaces. However, a number of other factors suggest that the technical requirements for ramps should not be changed at this time.

Most importantly, there are no data other than anecdotal evidence to discount older women as potential users of ramps. As a result, the 20-25% of people who use manual wheelchairs who had difficulty traversing slopes greater than 1:12, but only 15% at 1:12, are a major consideration in keeping the technical requirement for ramp slope at 1: 12. Nonetheless, further research with elderly users of wheelchairs might suggest the need for ramps with shallower slopes at facilities that have higher proportions of older people, such as senior centers, nursing homes, assisted-living facilities, and independent-living communities.

In addition, a number of factors related to the research design that were necessary to ensure subject safety may have created conditions that enhanced performances that would otherwise not have occurred in a real-world setting. First, subjects who participated may not have been truly representative of individuals in the mobility categories. Because subjects were self-selecting, it is likely that only individuals who thought that they could complete the test trials volunteered. As a result, participants were probably healthier and had better strength and stamina than others in the general population who use the same mobility aids. Second, for medical reasons, only subjects who were in good physical condition were permitted to participate. Third, because the ramp was located indoors in a climate-controlled setting, it was not subject to weather conditions such as rain or ice, which could adversely affect use. Fourth, in retrospect, the ramp itself may have been perceived to be safer and easier to use than ramps typically found in public settings. The test ramp was designed for use by one individual at a time. It was 3-feet wide and had handrails on both sides such that an individual could grab both rails at the same time. Although subjects were instructed to use only one rail, they had the option of using either one (in contrast to standard U.S. convention of always traveling to the right side) or both, if necessary. In addition, rails were provided at three heights, providing greater convenience than typically found in the real world. Therefore, it was not surprising that many subjects commented that they could not have traversed the ramp had it not been for their ability to use the handrails. However, in real-world situations, ramps other than ones located at private residences will be more than 3 feet in width in order to accommodate multiple users. Therefore, unless the effective width of a ramp is limited to 3 feet (i.e., a 3-foot maximum distance between handrails), which will require that all ramps be constructed in increments of 3-foot widths with intermediate handrails (e.g., a 6-foot-wide ramp with a handrail down the middle), many individuals who were able to traverse the entire length of the test ramp may not be able to do so in a real-world situation. Unfortunately, requiring ramps to have handrails no more than 3 feet apart seems to be costly and quite impractical, although it could be considered as equivalent facilitation if a ramp steeper than 1:12 is desired. Finally, the presence of the spotter on the ramp during the test trials probably biased the results. Although the spotter was not expected to, and did not, intervene unless necessary, several subjects stated that they would not have attempted to traverse the steeper gradients by themselves and only did so because the spotter was present. As such, even though individuals were able to traverse ramps steeper than 1: 12, they probably would not attempt to do so in real-life situations.

Therefore, based on the considerations outlined above, changes to the technical requirements for a maximum ramp slope of 1:12 and 30 feet in length were not recommended at this time. However, this issue should be considered again following further research directed at understanding the functional limitations of older wheelchair users as well as the impact of effective ramp width on ramp use.

One final word of caution. It is important to note that the requirement of a maximum slope of 1: 12, or 1-inch rise for 1-foot length, coincides with the English Standard measurement system. Therefore, ramps that are 1:12 should be easy to understand and practical to construct. Yet, it is still common to find ramps that do not comply with this requirement. If the construction industry has difficulty with a slope based on a 12-inch rule, how can we expect compliance with something that is not a standard increment measure, such as 1-inch rise for 14-inches in length? Therefore, until evidence to the contrary is overwhelming, common sense dictates that the technical requirement for ramps should remain at 1:12.

Acknowledgments: This work was supported in part by the U.S. Architectural and Transportation Barriers Compliance Board under contract number QA930020. In addition to the authors listed, the project team included Richard Duncan, Paula Guerette, Bettye Rose Connell, Ron Mace, Elaine Ostroff, Soni Gupta, and Leslie Jo.

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Originally published in Assistive Technology, Vol. 9, #1 (1997), p. 22-33.

Reprinted with permission from RESNA

 

A project of the National Resource Center on Supportive Housing and Home Modification,
in affiliation with the Fall Prevention Center of Excellence, funded by the Archstone Foundation.
Located at the University of Southern California Andrus Gerontology Center, Los Angeles, California 90089-0191 (213) 740-1364.