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Quantifying Mobility Scooter Performance in Winter Environments

  • Roger E. Montgomery
    Correspondence
    Corresponding author Roger E. Montgomery, MSc, KITE, Toronto Rehabilitation Institute – University Health Network, 550 University Ave, Toronto, ON, M5G 2A2, Canada.
    Affiliations
    KITE, Toronto Rehabilitation Institute, University Health Network, Toronto, Ontario
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  • Yue Li
    Affiliations
    KITE, Toronto Rehabilitation Institute, University Health Network, Toronto, Ontario
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  • Tilak Dutta
    Affiliations
    KITE, Toronto Rehabilitation Institute, University Health Network, Toronto, Ontario

    Institute of Biomedical Engineering University of Toronto, Toronto, Ontario

    Rehabilitation Sciences Institute, University of Toronto, Toronto, Ontario
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  • Pamela J Holliday
    Affiliations
    KITE, Toronto Rehabilitation Institute, University Health Network, Toronto, Ontario

    Department of Surgery, University of Toronto, Toronto, Ontario
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  • Geoff R Fernie
    Affiliations
    KITE, Toronto Rehabilitation Institute, University Health Network, Toronto, Ontario

    Institute of Biomedical Engineering University of Toronto, Toronto, Ontario

    Rehabilitation Sciences Institute, University of Toronto, Toronto, Ontario

    Department of Surgery, University of Toronto, Toronto, Ontario

    Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada
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Open AccessPublished:July 05, 2021DOI:https://doi.org/10.1016/j.apmr.2021.06.005

      Abstract

      Objectives

      To quantify mobility scooter performance when traversing snow, ice, and concrete in cold temperatures and to explore possible performance improvements with scooter winter tires.

      Design

      Cross-sectional.

      Setting

      Hospital-based research institute.

      Participants

      Two drivers (50 and 100 kg) tested 8 scooter models (N=8). Two mobility scooters were used for winter tire testing.

      Interventions

      Scooters were tested on 3 different conditions in a random sequence (concrete, 2.5-cm depth snow, bare ice). Ramp ascent and descent, as well as right-angle cornering up to a maximum of 10° slopes on winter conditions, were observed. Winter tire testing used the same slopes with 2 scooters on bare and melting ice surfaces.

      Main Outcome Measures

      Maximum achievable angle (MAA) and tire traction loss for ramp ascent and descent performance. The ability to steer around a corner on the ramp.

      Results

      All scooters underperformed in winter conditions, specifically when traversing snow- and ice-covered slopes (χ2 [2, N=8]=13.87-15.55, P<.001) and corners (χ2 [2, N=8]=12.25, P<.01). Half of the scooters we tested were unable to climb a 1:12 grade (4.8°) snow-covered slope without losing traction. All but 1 failed to ascend an ice-covered 1:12 grade (4.8°) slope. Performance was even more unsatisfactory for the forward downslopes on both snow and ice. Winter tires enhanced the MAA, permitting 1:12 (4.8°) slope ascent on ice.

      Conclusions

      Mobility scooters need to be designed with winter months in mind. Our findings showed that Americans with Disabilities Act–compliant built environments, such as curb ramps that conform to a 1:12 (4.8°) slope, become treacherous or impassible to mobility scooter users when covered in ice or snow. Scooter manufacturers should consider providing winter tires as optional accessories in regions that experience ice and snow accumulation. Additional testing/standards need to be established to evaluate winter mobility scooter performance further.

      Keywords

      List of abbreviations:

      MAA (maximum achievable angle), WMD (wheeled mobility device)
      Mobility scooter use has increased in recent years in part because of an aging population.
      • Smith EM
      • Giesbrecht EM
      • Mortenson B
      • Miller WC
      Prevalence of wheelchair and scooter use among community-dwelling Canadians.
      Snow and ice can create impassible barriers for mobility scooters on curb and accessibility ramps, even with ramps that conform to the current code of 1:12 grade for public buildings.
      • Lemaire ED
      • O'Neill PA
      • Desrosiers MM
      • Robertson G
      Wheelchair ramp navigation in snow and ice-grit conditions.
      Snow removal services do not always adequately clear these ramps and sidewalks. For example, the sidewalks of the City of Niagara Falls and the residential areas of the City of Toronto only have sidewalks plowed after an excess of 8 cm of snow has accumulated during select winter months.

      City of Niagara Falls. Winter maintenance policy plan. Available at: https://niagarafalls.ca/pdf/municipal-works/winter-maintenane-policy-plan-revised-march-8-2017.pdf. Accessed January 27, 2020.

      ,

      Infrastructure and Environment Committee. Sidewalk and transit snow clearing level of service table. Available at: https://www.toronto.ca/wp-content/uploads/2019/12/93fc-TS_Snow-Table-3_Sidewalks_2019_2022.pdf. Accessed January 27, 2020.

      This snow depth is significant because Lemaire et al
      • Lemaire ED
      • O'Neill PA
      • Desrosiers MM
      • Robertson G
      Wheelchair ramp navigation in snow and ice-grit conditions.
      showed that just 4 cm of snow cover resulted in challenges for wheelchair users. A recent survey found that over 95% of respondents in Manitoba reported getting their wheeled mobility device (WMD) tires stuck in the snow, and 92% had difficulty ascending slopes.
      • Ripat J
      • Brown CL
      • Ethans KD
      Barriers to wheelchair use in the winter.
      Reduced traction on winter surfaces may lead to increased safety risks for WMD users. For example, snow and ice may cause a scooter to slide off the sidewalk leading to tips, falls, and user injury.
      • Daveler B
      • Salatin B
      • Grindle GG
      • Candiotti J
      • Wang H
      • Cooper RA
      Participatory design and validation of mobility enhancement robotic wheelchair.
      ,

      Kleinschroth L. Mobility scooter use for community access: an exploration of individual and environmental factors on use and safety. Available at: http://summit.sfu.ca/item/18696. Accessed May 19, 2021.

      The increased difficulty with WMD operation in winter can result in a reduction in the number of people who use their device every day in winter compared with summer by 50%.
      • Ripat J
      • Brown CL
      • Ethans KD
      Barriers to wheelchair use in the winter.
      Reduced mobility can negatively affect one's quality of life.
      • Perry TE
      Seasonal variations and homes: understanding the social experiences of older adults.
      Therefore, it is crucial that we better understand the performance capabilities of current mobility scooters in winter.
      The objectives of this study were divided into 2 phases: phase 1 was to compare the steerability of a variety of 8 commonly used mobility scooters driving on simulated concrete as well as ice and snow covered surfaces. Phase 2A was to measure the slip resistance of the same 8 scooters. Phase 2B was to determine whether winter tires could improve the slip resistance.

      Methods

      Setting

      All testing took place in a climate-controlled laboratory. The laboratory is a 6.0-m × 5.6-m self-contained chamber with a 4.5-m × 4.9-m glycol refrigerated ice floor and 3.2-m ceiling height. The chamber is climatically controlled with an operable air temperature range of −10°C to 10°C.
      The ambient temperature was maintained at 0°C for phases 1 and 2A, and it was maintained at 4°C for bare (fully frozen) and 7°C for melting (partially frozen) ice conditions for phase 2B (table 1). Ice temperature was maintained between −3°C and −4°C for all testing except the melting ice condition, where it was kept at 0°C (see table 1).
      Table 1Ambient environmental conditions
      Surface TypeSurface Temperature (°C)Air Temperature (°C)Relative Humidity (%)Snow Density (kg/m3)Snow Hardness
      Snow hardness is measured on a 100-point scale: 50-70=soft pack snow, 70-84=medium pack snow.
      Single-axis platform – phase 1 (maneuverability testing)
      Concrete−3.75±0.34
      Ice temperature recorded not actual driving surface.
      −1.15±2.1575.05±0.13NANA
      Snow−3.76±0.34
      Ice temperature recorded not actual driving surface.
      −2.03±1.2776.02±0.09323.75±62.4566.35±7.29
      Ice−3.75±0.35−1.35±2.0979.02±0.07NANA
      Six-axis platform – phase 2A (slip resistance testing)
      Concrete−1.89±0.390.30±0.8873.67±0.04NANA
      Snow−3.02±0.30−0.32±0.5776.09±0.04378.89±26.6767.11±5.98
      Ice−3.68±0.690.21±0.9178.50±0.04NANA
      Single-axis platform – phase 2B (winter tire slip resistance testing)
      Bare Ice−3.004.05±0.12NDNANA
      Wet Ice0.007.08±0.49NDNANA
      NOTE. Values are mean ± SD.
      Abbreviations: NA, not applicable; ND, no data.
      low asterisk Snow hardness is measured on a 100-point scale: 50-70=soft pack snow, 70-84=medium pack snow.
      Ice temperature recorded not actual driving surface.

      Driving surfaces

      The scooters were driven on 3 surfaces: (1) snow-covered concrete; (2) bare ice (additionally melting ice for phase 2B); and (3) bare concrete. The simulated concrete driving surface was composed of (0.6 × 0.9m and 1.5 × 0.9m) plastic panels (ACC-S-3660-XX, ACC-S-2436-XXa) covered with an antislip coating (AS-150 grayb), which has similar frictional properties to concrete. The panels were secured with screws to help anchor the walkway to the ice floor. The corner driveway for steerability testing covered a 4.0-m × 3.7-m rectangular area, and the path was 0.9-m wide (fig 1A). The total straight driveway dimensions were 4.9 m × 0.9 m (fig 1B) and 3.0 m × 0.9 m for slip resistance testing and winter tire performance testing, respectively.
      Fig 1
      Fig 1(A) Steerability drive course (snow condition depicted): (1) cross-slope to up-slope; (2) up-slope to cross-slope; (3) cross-slope to down-slope; (4) down-slope to cross-slope. (B) Slip resistance drive course (concrete condition depicted).
      Snow was artificially created with the use of a snowmaker (All-Weather Snowmakerc) (fig 2A). Approximately 500 L of snow was collected over a 10.5±0.5-hour period from the snowmaker and transported to the laboratory before each testing session using a wheeled insulated cooler (All-Terrain 165d) (see fig 2B). The snow was stored on a plastic tarp within the laboratory for the duration of testing. At least 24 hours were given for the snow to settle and reach a stable density within the laboratory before it was used for testing. The snow was applied to the concrete panel driveway using a shovel, after which the test scooter was driven back and forth twice to compact the snow, creating a uniform surface. Finally, a custom-made levelling tool (see fig 2D, E) was raked across the driving surface to create a consistent 2.5-cm deep snow-covered driveway. Further, after each drive trial, the snow surface was groomed with a shovel and the leveling tool to maintain consistent snow conditions across all trials. The snow surface was considered adequately groomed when no tire tracks were visible. Snow consistency was monitored for density (Pocket 100e) (see fig 2C) and hardness (CTI Snow Penetrometerf) (see fig 2B) prior to each test session (see table 1).
      Fig 2
      Fig 2Standardized snow track creation: (A) all-weather snowmaker chamber; (B) snow hardness penetrometer, snow cooler, tactile panels; (C) snow density gauge; (D) snow grooming process with leveling tool; (E) detailed view of snow leveling tool, (A) steerability drive course, and (B) slip resistance drive course.

      Equipment

      For phase 2A testing, a 12-camera (Raptor-E digitalg) optical motion capture system was used to record the performance of each mobility scooter at 250 Hz. Three additional (Raptor-E digitalg) cameras were available and used during the phase 2B testing. Retro-reflective markers were affixed to the scooter body and wheels. Markers were also placed at specific points on the ice surface to identify where scooters started, steered, and stopped.
      A data logger (Smart Reader Plush) was used to collect surface and air temperature data during both phase 1 and phase 2A testing. Thermistors were placed on or embedded in the test condition surface or suspended at the height of ~0.3 m for air temperature. Relative humidity was recorded using built-in laboratory sensors.
      To simulate slope angles, the laboratory was secured on a single-axis (fig 3A), or 6-axis motion platform (see fig 3B), depending on test type. Phase 1 and phase 2B used the single-axis platform, and phase 2A testing was conducted with the 6-axis platform. Both motion bases were able to create static slope angles of up to 10° for the purpose of the test protocols. The scooter driver participants were asked to don protective equipment, including a helmet, insulated clothing, and a safety harness that was attached to an overhead robotic gantry to minimize injury risk. Collision barriers (mattresses) were also used at strategic locations as an added safety precaution.
      Fig 3
      Fig 3Laboratory on (A) single-axis motion platform and (B) 6-axis motion platform. Both platforms shown titled to 10°.
      Eight used mobility scooters were rentedi for testing during phase 1 and phase 2A protocols. The phase 2B protocol tested 2 lightly used mobility scooters that were donated. The winter tires tested in phase 2B were custom built with a milled aluminum wheel and winter tire (X-Ice Xi3j) tread segment secured to the wheel circumference with screw shank nails (fig 4). The combined wheel and tread formed a 25-cm diameter and 8-cm wide solid tire, similar in size to the stock pneumatic tires they were compared against. The scooter models varied in weight, 3- or 4-wheel design, tire type, and tread depth (table 2). Each mobility scooter was driven by the same 50-kg and 100-kg participants.
      Fig 4
      Fig 4(A) 4-wheeled Fortress 1700 DT with manufacturer installed tires. Frontal and profile views of a manufacturer installed tire shown to the right (B) 4-wheeled Fortress 1700 DT with prototype winter tires. Frontal and profile views of a prototype winter tire shown to the right.
      Table 2Mobility scooter characteristics
      ManufacturerModelWeight (kg)Wheel No.Wheel TypeAverage Tread Depth (mm)
      Values are mean ± SD.
      Phase 1 and 2A
      InvacareLynx L-342.843Solid1.25±0.07
      PrideGo-Go Elite Traveller48.234Solid1.21±0.37
      PrideGo-Go Elite Traveller Plus51.903Solid1.39±0.20
      PrideVictory 1079.953Solid1.27±0.92
      PrideVictory Twin90.243
      Scooter has dual front wheels.
      Solid1.59±0.32
      PrideVictory 10 DX93.514Pneumatic2.68±1.14
      Fortress1700 TA105.343Pneumatic3.02±0.90
      Fortress2000105.644Pneumatic1.76±0.68
      Phase 2B
      Fortress1700 DT112.44
      Manufacturer tires.
      /122.83
      Prototype winter tires.
      3Pneumatic
      Manufacturer tires.
      /solid
      Prototype winter tires.
      3.48±0.22
      Manufacturer tires.
      /7.78±0.85
      Prototype winter tires.
      Fortress1700 DT119.67
      Manufacturer tires.
      /133.54
      Prototype winter tires.
      4Pneumatic
      Manufacturer tires.
      /solid
      Prototype winter tires.
      3.29±0.23
      Manufacturer tires.
      /7.78±0.85
      Prototype winter tires.
      low asterisk Values are mean ± SD.
      Scooter has dual front wheels.
      Manufacturer tires.
      § Prototype winter tires.

      Protocol

      The protocol used in this study was approved by the hospital research ethics board (protocol 14-7692), and all participants provided their informed consent before participating. Participants were familiarized with each scooter before they drove them under test conditions. During testing, participants were instructed to sit upright with feet resting on the floor of the scooter chassis and to minimize body movement during each trial as indicated in electric wheelchair testing standards.

      International Organization for Standardization. Wheelchairs - part 2: determination of dynamic stability of electric wheelchairs. Available at: https://www.iso.org/standard/57753.html. Accessed May 25, 2018.

      Scooters were stored in a climate-controlled, indoor environment for at least 24 hours before testing. Within an hour before each testing session, participants had their clothed weight measured (Model 450KLk). Second, the tire pressure was measured and adjusted with the use of a pressure gauge (MotoMaster Aluminum Digital Tire Gaugel) and manual air pump (Via Velo Floor Bike Pumpm) for those scooters that had pneumatic tires. The tire pressure was adjusted to the maximum manufacturer recommended setting. Third, the forward scooter speed was adjusted to 1.0 m/s. The mobility scooters were then placed in the laboratory to sit for 30 minutes prior to the start of the test to allow for tire pressure to stabilize within the colder environment. The 30-minute wait before testing also simulated a reasonable time scooters may be exposed to winter temperatures based on an average trip length for scooter users of 7.2±0.5 km.
      • Sullivan J
      • La Grow S
      • Alla S
      • Schneiders A
      Riding into the future: a snapshot of elderly mobility scooter riders and how they use their scooters.

      Phase 1: steerability measurement

      This phase involved driving trials with 90° turns on 3 surfaces (bare ice, snow, concrete) on 0°, 3°, 6°, and 10° (uphill and downhill) slopes. Participants were asked to repeat each unique trial 3 times for each of the 8 scooters. There were 4 different 90° corners that participants attempted to negotiate in the forward direction. Successful navigation of a corner turn was defined by completing the turn while keeping the front tire(s) and at least 1 rear tire within the bounds of the 0.9-m wide drive path (see fig 1A). Extra leeway was permitted with the corners to better match the curb ramp landings size recommendations (1.2m) in current accessibility design guidelines.

      Newell WR. City of Ottawa accessibility design standards, 2nd ed. Available at: https://documents.ottawa.ca/sites/documents/files/documents/accessibility_design_standards_en.pdf. Accessed January 27, 2020.

      After each corner was completed, the scooter was brought to a stop.

      Phase 2A: slip resistance measurement (manufacturer installed tires)

      This phase involved both drive directions (forward, reverse) on the same 3 surfaces and slope angle selection as in phase 1 for each of the 8 scooters. Differing from phase 1, beyond the initial 4 slope angle conditions, when a scooter was unable to successfully complete an initial angle selection, the slope was incrementally decreased by 1° at a time to find the maximum achievable angle (MAA). The MAA score for each scooter was defined as the successful execution of drive instructions on at least 2 out of 3 attempts. Participants were instructed to begin each driving trial with the scooter's rear tires (or front tire[s] if reversing) on the edge of the driveway and then apply even and continuous throttle control to traverse the set path. Participants were instructed to drive along the path and release the throttle to bring the scooter to a stop within the last 0.6 m of the driveway as demarcated by floor markers. Participants were given 1.2 m or approximately 1 scooter length to brake within (see fig 1B). If scooters ended up outside of the pathway at any point either by loss of steering or braking control or if scooters lost sufficient traction, which stopped the motion of the device prematurely, the attempt was considered a failure. The reverse drive trials were conducted at approximately half the speed of forward trials, or about 0.5 m/s. The order in which each scooter attempted the different surface conditions was randomized.

      Phase 2B: slip resistance measurement (prototype winter tires)

      Prototype winter tire testing followed a similar protocol to phase 2A slip resistance testing except that initial slope angles were increased more gradually, 1° at a time. Only 2 scooters were tested for phase 2B (see table 2), with manufacturer installed tires (fig 4A) and custom-made winter tires (see fig 4B).

      Data analysis

      The motion capture data were processed using Cortex (version 5.2.0.1518) software.n These data were used to calculate all kinematic scooter performance measures including braking distance, peak velocity, and tire traction loss (tire slipping and skidding). Missing data were gap filled through cubic spline and rigid body virtual join interpolation methods. Velocity data were filtered with a second order, 4-Hz low pass Butterworth filter, and then calculations were performed on this data to find the scooter performance measures within MATLAB (2012b).o A tire slip or skid was defined by a difference >0.1 m/s between scooter chassis and tire velocity for >0.5 s.
      • Phetteplace G
      • Shoop S
      • Slagle T.
      Measuring lateral tire performance on winter surfaces.
      ,

      Ohri V. Developing test methods for the evaluation of scooter performance in winter conditions. Available at: http://hdl.handle.net/1807/43277. Accessed April 11, 2014.

      All parametric statistical tests were performed using SAS Enterprise Guide 7.1.p Parametric statistical tests took the form of repeated-measures analysis of variance with Bonferroni post hoc tests for multiple comparisons and paired t tests. Nonparametric data were analyzed through MATLAB (2015b)n in the form of Friedman tests with Bonferroni post hoc tests for multiple comparisons and Wilcoxon signed-rank tests.

      Results

      Phase 1: steerability measurement

      Figure 5 shows the steering performance for all scooters tested. The percentage score is the aggregate success rate of completing all 4 corners at all 4 slope angles (0°, 3°, 6°, 10°) with 3 attempts for the 2 drivers (in other words, the number of attempts that were successful of 96 attempts). All scooters had a near perfect (96.88%) success rate when completing corners on the concrete condition. A main effect for surface condition on cornering performance (χ2 [2, N=8]=12.25, P<.01) was observed with a Friedman test. Both ice and snow corner performance averaged at 35.68% and 31.25% successful corner completion, respectively. Post hoc tests showed that concrete performance was superior to ice (P<.05) and snow (P<.01). On all surfaces, the performance of the scooters was similar with only some minor differences. For example, the Fortress 2000 was unable to successfully complete any corners on the snow condition.
      Fig 5
      Fig 5Mobility scooter corner steering performance on winter surfaces. The scooter success rate was statistically higher on concrete than snow (P<.01) and ice (P<.05). Bars represent the mean. Error bars represent ±1SE.

      Phase 2A: slip resistance measurement (manufacturer installed tires)

      MAA performance

      Figure 6 shows the MAA performance (with and without traction loss observations) for all scooters tested for both upslope and downslope forward and reverse trials, respectively. All scooters, with the exception of the Go-Go 4W and Pride Victory 4W were able to complete up to 10° on concrete under all drive conditions. Friedman tests revealed significant differences (P<.001) for MAA performances across surface conditions regardless if traction loss observations were a factor or not. Post hoc comparisons revealed significantly better performance (P<.01) on concrete than ice under all situations. Some situations, such as reverse-drive up-slope, also showed statistically better MAA performance (P<.05) on concrete compared with snow. No scooters significantly outperformed each other. The figures generally show that snow and ice have a marked detrimental effect on the MAA and steerability for all scooters.
      Fig 6
      Fig 6Maximum achievable angle. Bars represent the mean for both 50- and 100-kg drivers. MAA results on the left and right side of the figure show MAA angles achieved when traction loss is and is not used, respectively, as a condition for determining if an angle is passed or failed. On all graphs: main effect ranges (χ2[2,N=8]=13.87-15.55, P<.001). Concrete MAA superior to ice MAA (P<.001) on both left and right sides of the graph, (A) forward upslope: snow MAA superior to ice MAA when ignoring traction loss (right side of the graph) (P<.05), (B) forward downslope: concrete MAA compared with snow MAA had P=.093 with traction loss (left side of the graph), (C) reverse upslope: concrete MAA superior to snow MAA (P<.05) on both sides of the graph, (D) reverse downslope: snow MAA superior to ice MAA when ignoring traction loss (right side of the graph) (P<.01).

      Braking distance and peak velocity

      Figure 7 depicts the average braking distance and peak velocity of all mobility scooters when driven forward on the level ground across differing surface conditions. A repeated-measures analysis of variance revealed a significant main effect of surface conditions on braking distance (F2.14=50.06, P<.001) and peak velocity (F2.14=15.66, P<.001). Post hoc tests showed a significant difference in braking distances between all 3 conditions (concrete vs snow [P<.05], concrete vs ice [P<.001], snow vs ice [P<.001]). Ice had the longest braking distance, whereas snow had the shortest. A significantly slower peak velocity was observed on snow compared with the other 2 conditions (snow vs concrete [P<.001], snow vs ice [P<.001]).
      Fig 7
      Fig 7Average level-ground braking distance and peak velocity across conditions. Ice had a longer braking distance than both concrete and snow (P<.001). Snow had shorter braking than concrete on level ground (P<.05). Snow also had a lower peak velocity than both concrete and ice (P<.001). Bars represent the mean for all 8 scooters tested. Error bars represent ±1SE.

      Phase 2B: slip resistance measurement (prototype winter tires)

      Figure 8 depicts the average MAA for 2 mobility scooters (Fortress 1700DT 4-wheel and 3-wheel) and 2 driver weights (50 kg and 100 kg) when driving on stock tires vs winter tires. Figure 8A represents upslope performance, whereas figure 8B conversely shows downslope performance. Paired t tests showed significantly better MAA performance for the forward downslope drives on bare ice (t[3]=−3.66, P=.0439), reverse downslope drives on bare (t[3]=−5, P=.0154) and melting ice (t[3]=−4.2, P=.0246) on winter tires compared with stock tires.
      Fig 8
      Fig 8Maximum achievable angle tests for stock and winter tires. (A) Upslope drives for both ice conditions and forward/reverse drives, (B) downslope drives for both ice conditions and forward/reverse drives. Scooter MAA performance was statistically better on winter tires when completing forward and reverse downslope drives on bare ice and reverse downslope drives on wet ice when using winter tires compared with stock tires (P<.05). Bars represent the mean for both 50 and 100 kg drivers. Error bars represent ±1SE. Abbreviations: FWD, forward drive; REV, reverse drive.

      Discussion

      Steerability

      Unsuccessful cornering attempts usually were due to understeering, with the scooters tending to continue traveling forward when the front tires were turned. Most of the weight of a scooter is placed on the rear tires because this is where the battery, seat, and driver are usually positioned. During piloting, we found that a commonly used scooter (Fortress 1700 4-wheel) with a 100-kg driver had an approximate weight distribution of 25% front and 75% rear. It is possible that shifting more weight forward toward the front tires to increase traction may help reduce understeering and therefore improve steerability on winter surfaces.

      Slope performance

      Where previous studies
      • Lemaire ED
      • O'Neill PA
      • Desrosiers MM
      • Robertson G
      Wheelchair ramp navigation in snow and ice-grit conditions.
      ,

      Smith L. Weathering the winter in a wheelchair. Available at: https://web.archive.org/web/20060321030543/http://www.rehabpub.com/ltrehab/10112000/4.asp. Accessed January 27, 2020.

      have linked snow-covered surfaces to underperformance of WMDs, we have observed similar results with mobility scooters. Half of the scooters we tested were unable to climb a 1:12 grade (4.8°) snow-covered slope without significant wheel slip. All scooters, except the Fortress 2000 model, failed to ascend an ice-covered 1:12 grade (4.8°) slope. Performance was even more unsatisfactory for the forward downslope drives on snow and ice. Forward downslope performance could have been improved by selecting a slower speed setting to reduce the amount of skidding. However, reversing downslope with a speed that was approximately half of the forward drive still resulted in significant skidding and a relatively low MAA on ice compared with concrete.
      Curb ramps do not always comply with guidelines and can often be much steeper than allowed.
      • Bennett S
      • Kirby RL
      • Macdonald B.
      Wheelchair accessibility: descriptive survey of curb ramps in an urban environment.
      Curb ramps can also become more challenging to negotiate with snowbanks and/or slush accumulation.
      • Li Y
      • Hsu JA
      • Fernie GR.
      Aging and the use of pedestrian facilities in winter - the need for improved design and better technology.
      The scooters that we tested struggled to perform adequately even on Americans with Disabilities Act–compliant slopes covered in snow and ice. Extrapolating our results with real-world observations would imply that mobility scooters are currently underperforming winter slope navigation and should be enhanced to deal with snow- and ice-covered slopes up to at least 6° (>1:10 gradient) to meet the needs of mobility scooter users throughout all seasons.

      Winter tire performance

      A recent study found that it would be feasible to create traction devices for wheelchairs in the winter to improve slip resistance and steerability.
      • Morales E
      • Lindsay S
      • Edwards G
      • et al.
      Addressing challenges for youths with mobility devices in winter conditions.
      Currently, winter tires are not readily available for mobility scooters. With customized solid 254-mm (10-in) diameter prototype winter tires, the 2 scooters that we tested had an improved upslope and downslope performance of 18.6% and 33.4%, respectively, compared with stock tires. Furthermore, although not statistically significant, forward upslope performance was improved from 4.5° to 6.3° with winter tires. This improvement means that where 1:12 (4.8°) Americans with Disabilities Act–compliant slopes were inaccessible with stock tires, slopes >1:10 (5.7°) are accessible with the customized winter tires.

      Study limitations

      All scooters were tested with tires of varying amounts of wear (see table 2). However, no scooter had tread wear that was less than the recommended amount according to manufacturer guidelines.

      ActiveCare Medical. ProwlerTM3310/3410 mobility scooter owner's manual. Available at: https://www.rehabmart.com/pdfs/prowler_manual_5_12.pdf. Accessed January 27, 2020.

      It is possible that scooter users may increase the speed of their devices beyond what we were able to safely test within the laboratory. Increased speed may reduce traction and increase braking distances.

      Conclusions

      All of the scooters we tested had difficulty driving on winter surfaces. This study provides evidence that current mobility scooters are ill designed to deal with winter conditions and that maintaining wheeled mobility year round remains a concern. This study also fills a knowledge gap
      • Ripat J
      • Sibley K
      • Giesbrecht E
      • et al.
      Winter mobility and community participation among people who use mobility devices: a scoping review.
      on mobility scooter performance and safety in winter. Improving the design of mobility scooters to handle winter environments through more rigorous testing as well as making winter tires available for purchase may help.

      Suppliers

      • a.
        ACC-S-3660-XX, ACC-S-2436-XX; Access Tile.
      • b.
        AS-150 gray; American Safety Technologies.
      • c.
        All-Weather Snowmaker; Snowtech Co Ltd.
      • d.
        All-Terrain 165; Igloo Products Corp.
      • e.
        Pocket 100; Brooks-Range Mountaineering Equipment.
      • f.
        CTI Snow Penetrometer; Smithers-Rapra.
      • g.
        Raptor-E digital; Motion Analysis Corp.
      • h.
        Smart Reader Plus; ACR Systems.
      • i.
        Mobility scooter; Inmotion Services Inc.
      • j.
        X-Ice Xi3; Michelin.
      • k.
        Model 450KL; Pelstar LLC/Health-o-meter Professional Scales.
      • l.
        MotoMaster Aluminum Digital Tire Gauge; Canadian Tire.
      • m.
        Via Velo Floor Bike Pump; Canadian Tire.
      • n.
        Cortex, version 5.2.0.1518; Motion Analysis Corp.
      • o.
        MATLAB 2012b; MathWorks.
      • p.
        SAS Enterprise Guide 7.1; SAS Institute.

      References

        • Smith EM
        • Giesbrecht EM
        • Mortenson B
        • Miller WC
        Prevalence of wheelchair and scooter use among community-dwelling Canadians.
        Phys Ther. 2016; 96: 1135-1142
        • Lemaire ED
        • O'Neill PA
        • Desrosiers MM
        • Robertson G
        Wheelchair ramp navigation in snow and ice-grit conditions.
        Arch Phys Med Rehabil. 2010; 91: 1516-1523
      1. City of Niagara Falls. Winter maintenance policy plan. Available at: https://niagarafalls.ca/pdf/municipal-works/winter-maintenane-policy-plan-revised-march-8-2017.pdf. Accessed January 27, 2020.

      2. Infrastructure and Environment Committee. Sidewalk and transit snow clearing level of service table. Available at: https://www.toronto.ca/wp-content/uploads/2019/12/93fc-TS_Snow-Table-3_Sidewalks_2019_2022.pdf. Accessed January 27, 2020.

        • Ripat J
        • Brown CL
        • Ethans KD
        Barriers to wheelchair use in the winter.
        Arch Phys Med Rehabil. 2015; 96: 1117-1122
        • Daveler B
        • Salatin B
        • Grindle GG
        • Candiotti J
        • Wang H
        • Cooper RA
        Participatory design and validation of mobility enhancement robotic wheelchair.
        J Rehabil Res Dev. 2015; 52: 739-750
      3. Kleinschroth L. Mobility scooter use for community access: an exploration of individual and environmental factors on use and safety. Available at: http://summit.sfu.ca/item/18696. Accessed May 19, 2021.

        • Perry TE
        Seasonal variations and homes: understanding the social experiences of older adults.
        Care Manag J. 2014; 15: 3-10
      4. International Organization for Standardization. Wheelchairs - part 2: determination of dynamic stability of electric wheelchairs. Available at: https://www.iso.org/standard/57753.html. Accessed May 25, 2018.

        • Sullivan J
        • La Grow S
        • Alla S
        • Schneiders A
        Riding into the future: a snapshot of elderly mobility scooter riders and how they use their scooters.
        N Z Med J. 2014; 127: 43-49
      5. Newell WR. City of Ottawa accessibility design standards, 2nd ed. Available at: https://documents.ottawa.ca/sites/documents/files/documents/accessibility_design_standards_en.pdf. Accessed January 27, 2020.

        • Phetteplace G
        • Shoop S
        • Slagle T.
        Measuring lateral tire performance on winter surfaces.
        Tire Sci Technol. 2007; 35: 56-68
      6. Ohri V. Developing test methods for the evaluation of scooter performance in winter conditions. Available at: http://hdl.handle.net/1807/43277. Accessed April 11, 2014.

      7. Smith L. Weathering the winter in a wheelchair. Available at: https://web.archive.org/web/20060321030543/http://www.rehabpub.com/ltrehab/10112000/4.asp. Accessed January 27, 2020.

        • Bennett S
        • Kirby RL
        • Macdonald B.
        Wheelchair accessibility: descriptive survey of curb ramps in an urban environment.
        Disabil Rehabil Assist Technol. 2009; 4: 17-23
        • Li Y
        • Hsu JA
        • Fernie GR.
        Aging and the use of pedestrian facilities in winter - the need for improved design and better technology.
        J Urban Health. 2013; 90: 602-617
        • Morales E
        • Lindsay S
        • Edwards G
        • et al.
        Addressing challenges for youths with mobility devices in winter conditions.
        Disabil Rehabil. 2018; 40: 21-27
      8. ActiveCare Medical. ProwlerTM3310/3410 mobility scooter owner's manual. Available at: https://www.rehabmart.com/pdfs/prowler_manual_5_12.pdf. Accessed January 27, 2020.

        • Ripat J
        • Sibley K
        • Giesbrecht E
        • et al.
        Winter mobility and community participation among people who use mobility devices: a scoping review.
        Arch Rehabil Res Clin Transl. 2019; 2100018