People with mobility impairments in the United States today and in 2010

Novel system identification method and multi-objective-optimal multivariable disturbance observer for electric wheelchair

Electric wheelchair (EW) is subject to diverse types of terrains and slopes, but also to occupants of various weights, which causes the EW to suffer from highly perturbed dynamics. A precise multivariable dynamics of the EW is obtained using Lagrange equations of motion which models effects of slopes as output-additive disturbances. A static pre-compensator is analytically devised which considerably decouples the EW's dynamics and also brings about a more accurate identification of the EW. The controller is designed with a disturbance-observer (DOB) two-degree-of-freedom architecture, which reduces sensitivity to the model uncertainties while enhancing rejection of the disturbances. Upon disturbance rejection, noise reduction, and robust stability of the control system, three fitness functions are presented by which the DOB is tuned using a multi-objective optimization (MOO) approach namely non-dominated sorting genetic algorithm-II (NSGA-II). Finally, experimental results show desirable performance and robust stability of the proposed algorithm.

Why is walker-assisted gait metabolically expensive?

Walker-assisted gait is reported to be ∼200% more metabolically expensive than normal bipedal walking. However, previous studies compared different walking speeds. Here, we compared the metabolic power consumption and basic stride temporal-spatial parameters for 10 young, healthy adults walking without assistance and using 2-wheeled (2W), 4-wheeled (4W) and 4-footed (4F) walker devices, all at the same speed, 0.30m/s. We also measured the metabolic power demand for walking without any assistive device using a step-to gait at 0.30m/s, walking normally at 1.25m/s, and for repeated lifting of the 4F walker mimicking the lifting pattern used during 4F walker-assisted gait. Similar to previous studies, we found that the cost per distance walked was 217% greater with a 4F walker at 0.30m/s compared to unassisted, bipedal walking at 1.25m/s. Compared at the same speed, 0.30m/s, using a 4F walker was still 82%, 74%, and 55% energetically more expensive than walking unassisted, with a 4W walker and a 2W walker respectively. The sum of the metabolic cost of step-to walking plus the cost of lifting itself was equivalent to the cost of walking with a 4F walker. Thus, we deduce that the high cost of 4F walker assisted gait is due to three factors: the slow walking speed, the step-to gait pattern and the repeated lifting of the walker.

Wheelchair-related falls in veterans with spinal cord injury residing in the community: a prospective cohort study

OBJECTIVES

(1) To determine the incidence of wheelchair falls and fall-related injuries in persons with spinal cord injury (SCI) living in the community. (2) To predict wheelchair-related falls and associated injuries from specific parameters including characteristics of the wheelchair user, wheelchair type and features, health care practices, wheelchair activities, and physical environment.

DESIGN

This prospective cohort study followed participants monthly over 1 year; data were collected through surveys, interviews, performance testing, observation, and medical records.

SETTING

Three Veterans' Administration hospitals.

PARTICIPANTS

Convenience sample of community-dwelling persons with SCI who used a wheelchair as their primary means of mobility (N=702).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Self-reports of wheelchair falls and fall-related injuries, Wheelchair User Characteristics Survey, Health Status Checklist, Health-Related Behaviors, Zuckerman Sensation Seeking Scale, Wheelchair and Equipment-Related Behaviors, Wheelchair Characteristics, Wheelchair Skills Test, and Physical Environment Assessment.

RESULTS

Of the 659 subjects who completed the study, 204 participants (31%) reported 553 fall events, and 95 subjects (14%) were injured as a result of wheelchair falls. A logistic regression model for predicting wheelchair falls identified 6 significant risk factors: pain in previous 2 months, alcohol abuse, greater motor function, history of previous fall, fewer SCI years, and shorter length of wheelchair. Eighty-two percent of the variance for wheelchair fall events was explained by these 6 variables. A logistic regression model for predicting injurious falls identified 4 significant risk factors: pain in previous 2 months, greater motor function, history of previous fall, and inaccessible home entrance. These 4 factors were able to explain 81% of the variance for injurious falls.

CONCLUSIONS

This is the first study to determine the incidence of wheelchair-related falls in community-dwelling people with SCI who use a wheelchair. Results indicate the incidence of falls was 31% and injurious falls was 14%. Those at greatest risk can be predicted from some readily available information regarding their clinical status, wheelchair features, and home environment.

Reliability and validity of the telephone administration of the wheelchair outcome measure (WhOM) for middle-aged and older users of power mobility devices

OBJECTIVE

To examine the measurement properties of the tele-phone administration of the Wheelchair Outcome Measure (WhOM).

SUBJECTS

Power mobility device users aged 50-89 years.

METHODS

Two independent cohorts were recruited: (i) a prospective cohort (n = 40) to estimate test-retest reliability and to determine the applicability of the telephone format, and (ii) a cross-sectional cohort to examine construct validity with 3 groups: (a) people waiting for a first power mobility device (n = 44); (b) initial users (n = 35; 1-6 months); and (c) long-term users (n = 39; 12-18 months).

RESULTS

The tool demonstrated good test-retest reliability (intraclass correlation coefficient 0.77-1.00), took 10.9 min (standard deviation = 5.2) to administer and was practical to use over the telephone. Validity testing showed moderate correlations with the Quebec User Evaluation of Satisfaction with Technology (rS = 0.36-0.45) and the Psychosocial Impact of Assistive Devices Scale (rS = 0.31-0.43). WhOM scores could discriminate non-users from users (wait-list vs initial users; wait-list vs long-term users, p < 0.001) and power wheelchair from scooter users (total WhOM scores, p < 0.05).

CONCLUSION

The WhOM is a stable, valid and applicable measure for telephone administration with older power mobility device users. It is moderately linked to satisfaction with the device and to the psychosocial impact of the device, and therefore complements rather than replaces those measures.

Towards an intelligent wheelchair system for users with cerebral palsy

This paper describes and evaluates an intelligent wheelchair, adapted for users with cognitive disabilities and mobility impairment. The study focuses on patients with cerebral palsy, one of the most common disorders affecting muscle control and coordination, thereby impairing movement. The wheelchair concept is an assistive device that allows the user to select arbitrary local destinations through a tactile screen interface. The device incorporates an automatic navigation system that drives the vehicle, avoiding obstacles even in unknown and dynamic scenarios. It provides the user with a high degree of autonomy, independent from a particular environment, i.e., not restricted to predefined conditions. To evaluate the rehabilitation device, a study was carried out with four subjects with cognitive impairments, between 11 and 16 years of age. They were first trained so as to get acquainted with the tactile interface and then were recruited to drive the wheelchair. Based on the experience with the subjects, an extensive evaluation of the intelligent wheelchair was provided from two perspectives: 1) based on the technical performance of the entire system and its components and 2) based on the behavior of the user (execution analysis, activity analysis, and competence analysis). The results indicated that the intelligent wheelchair effectively provided mobility and autonomy to the target population.

Impact of wheelchair acquisition on social participation

PURPOSE

Efficient mobility could be a prerequisite to carrying out many daily activities and social roles (social participation). The aim of this study was to assess the impact of wheelchair acquisition on social participation.

METHODS

Single group pre/post design where the intervention was the acquisition of a wheelchair paid for by the provincial government. Data were collected retrospectively from the participants' medical files. Individuals were excluded if they received an assistive device other than a wheelchair or contacted the centre only for wheelchair repairs. Social participation was measured using the Reintegration to Normal Living Index (RNLI) questionnaire.

RESULTS

The sample (n = 42) had a mean age of 64.2 +/- 18.5 years, and 50% of them (n = 21) did not have a wheelchair before the intervention. The total RNLI scores pre- (46.9/100 +/- 24.7) and post-acquisition (29.7/100 +/- 18.5) showed a significant improvement in participation (p < 0.001). No difference was found between those who had their first wheelchair (n = 21) compared with replacement. Single-item analysis of the RNLI showed a significant difference for 5 of the 11 items. Age and diagnosis were significantly correlated (p < 0.05) with some of the items.

CONCLUSION

Social participation improved significantly following wheelchair acquisition although confounding variables may have contributed to this improvement.

Promoting independence for wheelchair users: the role of home accommodations

PURPOSE

The objective of this research is to investigate whether home accommodations influence the amount of human help provided to a nationally representative sample of adults who use wheelchairs.

DESIGN AND METHODS

We analyzed data from the Adult Disability Follow-back Survey (DFS), Phase II, of the Disability Supplement to the 1994-1995 National Health Interview Surveys (NHIS-D). The analytic sample consisted of 899 adults aged 18 and older who reported using wheelchairs in the previous 2 weeks. We conducted logistic regression and ordinary least squares (OLS) regression analyses to test the influence of home accommodations on the receipt of any human help, and among respondents who received help, on the hours of help received, respectively. We analyzed paid and unpaid help separately.

RESULTS

Home accommodations were related to the receipt of unpaid, but not paid, help. Relative to having no home accommodations, the presence of each additional accommodation decreased the odds of having unpaid help by 14% (OR =.86; 95% CI =.76,.97). Additionally, we observed an inverse relationship between the number of accommodations in the home and hours of unpaid help (p <.01). For wheelchair users who live alone, specific types of home accommodations were also inversely related to hours of unpaid help.

IMPLICATIONS

Policies that reimburse for home accommodations may be an efficient response to the growing demand for home-care support while enabling greater autonomy and independence for people who use wheelchairs.

Development of the Seating and Mobility Script Concordance Test for Spinal Cord Injury: Obtaining Content Validity Evidence

The appropriateness of a consumer's seating and mobility system varies considerably depending on the competence, proficiency, and experience of the professionals assisting the user. At present, there is a scarcity of skilled and knowledgeable therapists to evaluate and recommend seating and mobility devices. There is also a lack of measurement tests available to evaluate the impact of educational experiences or clinical practice on the ability to make specialized clinical decisions about seating and mobility needs. The Seating and Mobility Script Concordance Test (SMSCT) is a new assessment tool, grounded in the hypothetico-deductive and schema theories of clinical reasoning. The test is designed to assess therapists by examining the organization of their knowledge, associations between items of their knowledge, and the adequacy of their clinical decisions as compared to expert consensus. This article describes the interview, test development, and content/item review processes used for the collection of content validity evidence. The iterative process employed and the appraisal of the content validity evidence that resulted in the final version of the SMSCT are presented. The SMSCT appears to be a promising assessment tool representing content within the domain of seating and mobility for individuals with spinal cord injuries. The process utilized to develop the SMSCT in spinal cord injury can be replicated for other diagnoses and domains.

The manual wheelchair-handling skills of caregivers and the effect of training

OBJECTIVE

To test the hypothesis that the Wheelchair Skills Training Program (WSTP) is effective in improving the wheelchair-handling skills of untrained caregivers.

DESIGN

Within-participant comparisons.

SETTING

Rehabilitation center and community.

PARTICIPANTS

Twenty-four caregivers of manual wheelchair users.

INTERVENTIONS

Caregiver participants underwent the WSTP, version 2.4, adapted for caregivers. Training was individualized on the basis of an integrated testing-and-training protocol that took place on a single occasion (total, approximately 50 min).

MAIN OUTCOME MEASURES

Total percentage scores on the objective Wheelchair Skills Test (WST), version 2.4, for the pretraining (N=24), posttraining (N=24), and retention (n=9) evaluations. For the skill-transfer evaluation (n=10), we used the questionnaire version (WST-Q), administered by telephone to participants after return to their communities.

RESULTS

There were no serious adverse incidents. The mean pretraining total WST score +/- standard deviation was 77.8%+/-12.0%. Posttraining, this increased to 94.7%+/-7.1% (P <.001), a 22% relative increase. At retention testing, a median latency of 7 days later, the mean value, 94.2%+/-7.1%, did not decrease significantly from the posttraining level (P =.38). At skill-transfer testing, a median latency of 179 days posttraining, the mean value, 92.5%+/-8.7%, did not decrease significantly from the posttraining level (P =.73). The greatest improvements were at the advanced skill level.

CONCLUSIONS

The WSTP is a safe, practical, and effective method of improving the wheelchair-handling skills of untrained caregivers. Skill improvements are generally well retained and transfer well to the community. Such training could play an important role in the rehabilitation process.

Wheelchair skills training program for clinicians: a randomized controlled trial with occupational therapy students

OBJECTIVE

To test the hypothesis that a brief formalized period of wheelchair skills training, added to the standard curriculum, results in significantly greater overall improvements in wheelchair skills than a standard undergraduate occupational therapy (OT) curriculum alone.

SETTING

Rehabilitation center.

DESIGN

Randomized controlled trial.

PARTICIPANTS

Eighty-two students in a university undergraduate OT program.

INTERVENTIONS

All students received the standard university curriculum. The 22 second-year students, randomly allocated to the Wheelchair Skills Training Program (WSTP) group, were also trained (on a single occasion each, in groups of 1-3 at a time) on the 50 skills that make up the WSTP. The mean +/- standard deviation (SD) training time was 121.2+/-33.5 minutes per group.

MAIN OUTCOME MEASURE

Total percentage score on the Wheelchair Skills Test (WST), Version 2.4.

RESULTS

From before to after intervention, second-year students in the WSTP group increased their mean percentage WST scores +/- SD from 64.8%+/-9.0% to 81.0%+/-5.2%, a 25% improvement (P<.001). Over a comparable period, the 18 students in the second-year control group increased from 66.0%+/-8.0% to 72.4%+/-7.1%, a 9.7% improvement (P=.015). The WSTP group improved to a significantly greater extent (P=.005). For a subset of 8 students in the WSTP group who were retested 9 to 12 months later, the mean WST score was 79.7%+/-4.1%, not significantly less than their WST 2 scores (P=.29). The mean WST score for the 42 students in the fourth-year control group was 73.9%+/-4.1%, significantly lower than the mean postintervention WST score of the second-year students in the WSTP group (P< .0001) and not different from the second-year control group (P=.58).

CONCLUSIONS

The WSTP is an effective way to improve the wheelchair-skills performance of OT students. This has implications for the education of all rehabilitation clinicians.

Evaluation of selected electric-powered wheelchairs using the ANSI/RESNA standards

OBJECTIVES

To compare the performance characteristics of different electric-powered wheelchairs (EPWs) and to evaluate the effectiveness of the American National Standards Institute/Rehabilitation Engineering and Assistive Technology Society of North America (ANSI/RESNA) wheelchair standards.

DESIGN

Five types of EPWs were selected. Three wheelchairs of each type were tested according to the ANSI/RESNA wheelchair standards.

SETTING

Rehabilitation engineering center.

SPECIMENS

Fifteen wheelchairs.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Static tipping angle; dynamic tipping score; braking distance; energy consumption; static, impact, and fatigue strength; and climatic conditioning.

RESULTS

There were significant differences (P<.05) among the 5 types of EPWs for static stability when facing both uphill and downhill in the most-stable and least-stable configurations. There were significant differences (P<.05) among the EPWs on most of the dynamic stability tests. There were also significant differences (P<.05) among EPWs for all the effectiveness of brakes conditions, as well as between 2 wheelchairs for the energy consumption testing. There were several failures among the wheelchairs during the static, impact, and fatigue strength testing and during the climatic testing.

CONCLUSIONS

The results show that EPWs can vary greatly with respect to static and dynamic stability, braking distance, range, strength testing, and climatic conditioning. All these factors have a substantial effect on safety and performance.

Wheelchair skills training program: a randomized clinical trial of wheelchair users undergoing initial rehabilitation11No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated

OBJECTIVE

To test the hypothesis that a brief, formalized period of additional wheelchair skills training is safe and results in significantly greater improvements in wheelchair skills performance than a standard rehabilitation program.

DESIGN

Randomized controlled trial.

SETTING

Rehabilitation center.

PARTICIPANTS

Thirty-five wheelchair users (20 with musculoskeletal disorders, 15 with neurologic disorders) admitted for initial rehabilitation. Subjects' mean age +/- standard deviation (SD) was 59+/-18.3 years.

INTERVENTION

Subjects randomly allocated to the treatment group participated in the Wheelchair Skills Training Program (WSTP), averaging 4.5+/-1.5 training sessions, each 30 minutes long. Subjects in the control group did not receive any wheelchair skills training beyond that given in a typical rehabilitation stay.

MAIN OUTCOME MEASURES

Wheelchair Skills Test (WST), version 2.4, before and after training. Changes in total percentage WST score and individual skill scores were examined.

RESULTS

There were no adverse incidents. The control group's mean percentage score +/- SD increased from 60.1%+/-14.4% to 64.9%+/-13.3%, an 8% improvement of the posttest relative to the pretest (P=.01). The WSTP group's mean score increased from 64.9%+/-9.4% to 80.9%+/-5.6%, a 25% improvement of the posttest relative to the pretest (P<.000). The WSTP group showed significantly greater improvements than the control group (P<.000). Among the specific skills, significantly greater improvements were seen in the WSTP group for the gravel and high-curb descent skills (P<.001).

CONCLUSIONS

The WSTP is safe and practical and has a clinically significant effect on the independent wheeled mobility of new wheelchair users. These findings have implications for the standards of care in rehabilitation programs.

Ambulation aid use during the rehabilitation of people with lower limb amputations

Our objective was to describe the progression of ambulation aid use by people with lower limb amputations during their initial rehabilitation. We prospectively studied 37 people with recent lower limb amputations and a mean (SD) age of 68 (13) years. Subjects were evaluated each weekday during gait-training physiotherapy sessions, and the type and order of ambulation aids used during ambulation training were documented. The total number of gait-training sessions that we observed was 605, with a mean (SD) of 16.4 (7.7) sessions per participant and a range of 5-47. Of the 37 participants, 33 (89%) were discharged with prostheses. The mean (SD) number of aids per person was 2.9 (1.0). The percentage of participants who used each aid (presented in the mean order in which they were first used) were 76% parallel bars, 60% four-footed walkers, 81% two-wheeled walkers, 11% two crutches, 8% four-wheeled walkers, 46% two canes, and 14% one cane. People with lower limb amputations generally use a number of ambulation aids in a fairly consistent order as they progress through their initial rehabilitation. These findings have implications for the process of providing ambulation aids and provide a foundation for further study.

Folding and unfolding manual wheelchairs: an ergonomic evaluation of health-care workers

The objective of this study was to test the hypotheses (i) that health-care workers vary greatly in the methods used to fold and unfold selected manual wheelchairs, and (ii) that many of the methods used include bent and twisted back postures that are known to be associated with a high risk of injury. We studied 20 health-care workers in a rehabilitation center. Subjects folded and unfolded two wheelchairs of cross-brace design, one with and one without a sling seat. As outcome measures, we used a questionnaire, time taken, visual analog scales of perceived exertion and back strain, folded width, videotape and Ovako Working Posture Analysis System (OWAS) back scores (1-4). Subjects used up to 14 different combinations of approach, hand placement and back posture to accomplish the tasks. The mean OWAS scores were in the 2.4-3.1 range and 49 (42%) of the 118 scores recorded were class 4 (back simultaneously "bent and twisted", considered to be associated with the highest risk of injury). We also observed methods that appeared to be safe and effective. Age, gender, profession, experience and seat condition did not generally influence the outcome measures. We conclude that health-care workers use a variety of methods to fold and unfold wheelchairs, many of which include bent and twisted back postures that may carry a risk of injury. Further study is needed to confirm this risk, to identify more ergonomically sound wheelchair designs and to develop better methods of carrying out the common and important task of folding and unfolding wheelchairs.

The Wheelchair Skills Test: a pilot study of a new outcome measure

OBJECTIVE

To evaluate the practicality, safety, reliability, validity, and usefulness of a new Wheelchair Skills Test (WST).

DESIGN

A pilot study with within-subject comparisons.

SETTING

Rehabilitation center.

PATIENTS

Twenty-four wheelchair users (11 with amputations, 4 with stroke, 3 with musculoskeletal disorders, 3 with spinal cord injury, 3 with neuromuscular disorders).

INTERVENTION

The WST.

MAIN OUTCOME MEASURES

Subjects were videotaped while performing 33 skills twice (>10d apart). Their ability to perform each skill was rated on a 3-point ordinal scale. The test-retest, intra-, and interrater reliabilities were determined. Each subject's occupational therapist completed a visual analog scale (VAS), reflecting a global rating of the subject's manual wheelchair skills. We assessed validity by evaluating whether the WST detected expected changes (construct validity) and how well the total WST scores correlated with the occupational therapists' global ratings (concurrent validity). Each occupational therapist also used a VAS to quantify the usefulness of the WST.

RESULTS

The mean time required to administer the WST was 29 minutes. There were no adverse incidents. For the test-retest, intra-, and interrater reliabilities, the correlations for the total scores were .65 (P =.001), .96 (P <.001), and .95 (P <.001), respectively. The 9 therapists unanimously endorsed 30 (91%) of the 33 WST skills. The correlation between the mean changes in the WST and global rating scores was .45 (P <.05). There was a slight negative relationship between total WST score and age (P <.05). There were no significant differences related to the diagnoses accounting for wheelchair use. Wheelchair users with more than 3 weeks of experience with their wheelchairs scored higher than those with less experience (P =.0085). The correlations between the WST and global rating scores ranged from .40 to .54 (P <.05). Through Rasch analysis, we eliminated 6 skills, with the remaining skills comprising a unidimensional screening test of wheelchair ability. The mean VAS score for perceived usefulness was 59%.

CONCLUSIONS

The WST is practical, safe, well tolerated, exhibits good to excellent reliability, excellent content validity, fair construct and concurrent validity, and moderate usefulness. This pilot study makes an important contribution toward meeting the need for a well-validated outcome measure of manual wheelchair ability.

Wheelchair armrest strength testing

There are about 1.4 million manual wheelchair users, 100,000 electric-powered wheelchair users, and 60,000 electric-powered scooter users. The current study was undertaken to determine if the fasteners of a clamp-type armrest receiver were prone to failure. The first test was used to examine the potential misalignment of the armrest receiver components that attach it to the frame. The second test was to evaluate the entire armrest using the American National Standards Institute/Rehabilitation Engineering and Assistive Technology Society of North America armrest static strength standard. Finally, we conducted three fatigue tests. The first fatigue test was performed by repeating the static stability tests multiple times. The last two tests were a modified version of the double-drum wheelchair fatigue test used to apply repeated loading and vibration simultaneously. A paired t-test showed that there is no statistically significant difference (p = 0.08), with a confidence of 95%, between critical alignment measurements. The armrest including the receiver passed the standard requirement of a force of 760 N being applied outward at 15 degrees. During fatigue testing, we found that armrests did not exhibit any visible or functional damage. Upon completion of the tests, the armrests and receivers functioned properly. At about 100,289 cycles on a double-drum test machine, three bolts failed on each armrest receiver when the screws were loosened to have only five threads engaged prior to commencing the test. The design of the armrest tested was in compliance with existing national and international standards. Currently, both International Standards Organization and American National Standards Institute/Rehabilitation Engineering and Assistive Technology Society committees are developing standards for seating systems that will include static, impact, and fatigue strength testing of devices like lateral torso supports, lateral hip support, etc. Methods similar to those explored in this study should be considered. This study may help manufacturers when designing products and purchasers or regulatory agencies when attempting to evaluate the safety and quality of armrest assemblies.

The voice of the customer: consumers define the ideal battery charger

The Rehabilitation Engineering Research Center on Technology Evaluation and Transfer is exploring how the users of assistive technology devices define the ideal device. This work is called the Consumer Ideal Product program. The results show what device characteristics are most and least important, indicating where to place the priority on product features and functions from the consumer's perspective. The "voice of the customer" can be used (1) to define the ideal characteristics of a product, (2) to make trade-offs in product design and function improvements based on their relative importance to the consumer, (3) to compare the characteristics of existing products against the characteristics of the ideal product, or (4) to generate a product checklist for consumers to use when making a purchase decision. This paper presents the results of consumers' defining the ideal battery charger. Four focus groups generated the survey's content, then 100 experienced users rated 159 characteristics organized under 11 general evaluation criteria. The consumers placed the highest importance on characteristics from the general evaluation criteria of product reliability, effectiveness, and physical security/safety. The findings should help manufacturers and vendors improve their products and services and help professionals and consumers make informed choices.

An analysis of the effects of ramp slope on people with mobility impairments

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.