Anthropometry of Wheeled Mobility Project: Final Report

4.3.5 Turning clearance

The ADA-ABA Standards include requirements for a circular turning space, a T shaped turning space, a L-Turn (90-degree turn) and a U-Turn (180-degree turn) around an obstacle. In our research several turning maneuvers were studied: the 360-degree turn, the 180-degree turn, the 180-degree turn around a barrier and a 90-degree turn. In confined dead end spaces, a 360-degree turn should be used as the basis for the minimum space required since individuals often move around within small space without actually leaving it. A 180-degree turn is more appropriate as a basis for defining a minimum space bounded only on two sides and the individual has an open space to use along the axis of the turn. T shaped space is not included here because it can be derived from the 90-degree turn to establish the width of the arms of the T and the clear floor space to determine the length of each arm. The overall width should be the same in both arms. The same values should be used for the 90-degree turn and the T-turn.

The accommodation models and our recommendations are addressed individually below. In general, standards should give some guidance on where each of these turning spaces should be used. For example, the 180-degree turn around an obstruction should be used at ramp landings rather than the 180-degree unobstructed turn clearance.

4.3.5.1 90-Degree Turn

This turning clearance is applicable for exterior and interior circulation, aisles in seating areas, ramps and other locations. The width of circulation spaces should be wider to accommodate two-way traffic and egress requirements.

The mean values for scooters in our sample are in excess of the current standards. In addition, less than 80% of power and manual wheelchair users in our sample are accommodated by the standard. We recommend revising the ADA-ABA standard for 90-degree turning width to 1000 mm (39 in.) which would accommodate at least 95% of our sample. Figure 4‒4 shows the accommodation model of the minimum clear width required for the 90-degree turn.

Figure 4-4: Accommodation model depicting the minimum clear width required by users of manual wheelchairs, powered wheelchairs and scooters to complete a 90-degree turn.

Long Description: This data depicts the amount of space required by users of wheeled mobility devices to perform a 90-degree turn ("L-Turn"). The bold dashed line in the table and figure indicates the current ADA requirement of a 91.5 cm (36 in.) passage width. Findings from the Anthropometry of Wheeled Mobility Study indicate that a width of at least 85 cm (33 in.) was required for 50% of the manual and power wheelchair users measured in this study to perform a 90-degree turn. A width of 100 cm (39 in.) was required in order for 95% of manual wheelchair and power chair users to complete the turn, with 95% of scooter users needing a width of at least 110 cm (43 in.) These data are based on measurements of wheeled mobility users performing 90-degree turns in a hallway, built with mock walls. The outside wall of the hallway was fixed. The other side of each leg had moveable walls. The enclosed space was incrementally increased until a user could pass through the turn successfully. The minimum space required for completing a 90-degree turn within moving or knocking down any of the walls was recorded. Use of multiple short turns was allowed in contrast to a single continuous turn.

4.3.5.2 180-degree turn

Currently, the ADA-ABA does not have a specific clearance for this type of turn. The 1525 mm (60 in.) turning space would be used instead. Our research findings for this turn apply to corridors and other circulation spaces are bounded by two parallel walls or three walls. Our findings indicated that a width of 1700 mm (67 in.) would accommodate 95% of manual and power wheelchair users and 90% of the scooter users. Accommodation of additional scooter users would increase this dimension by 18 mm (7 in.) (Figure 4‒5).

Figure 4-5: Accommodation model depicting the minimum clear width required by users of manual wheelchairs, powered chairs and scooters to complete a 180-degree turn.

Long Description: This data depicts the amount of space required by users of wheeled mobility devices to perform a 180-degree turn. The bold dashed line in the table and figure indicates the current ADA requirement of a 152.5 cm (60 in.) space for wheeled mobility users to turn around. Findings from the Anthropometry of Wheeled Mobility Study indicate that a width of at least 130 cm (51 in.) was required for 50% of the manual wheelchair users measured in this study to perform a 90-degree turn. A width of 170 cm (67 in.) was required in order for 95% of manual wheelchair and power chair users to complete the turn, with 95% of scooter users needing a width of at least 210 cm (83 in.) These data are based on measurements of wheeled mobility users performing 180-degree turns in a dead-end hallway, built with mock walls. The end wall and a second wall of the hallway were fixed. The other side of the hallway had a moveable wall. The hallway width was incrementally increased until a user could enter the space, turn around, and exit the space successfully. The minimum space required for completing 180-degree turn within moving or knocking down any of the walls was recorded. Use of multiple short turns was allowed in contrast to a single continuous turn.

4.3.5.3 180-degree turn around an obstacle

This type of turn is applicable to turning at a landing where one is reversing direction to move back along a parallel path, e.g. at the end aisles in library stacks or supermarkets, at switchback ramps or in a terminal queue. The current ADA-ABA standard for the space needed to complete maneuver is based on the width of the entry aisle and the width of the intervening obstacle, e.g. shelving. In our research, we studied the impact of keeping the depth of the turning area and the entry/egress aisle width identical. This provided the opportunity to discover if a wider aisle would lead to less required depth in the turning area. This was, in fact, the case. The accommodation model depicts the results with the condition that depth is the same as access and egress aisle width. We found that a width of 1065 mm (42 in.) for all three dimensions would accommodate more than 90% of the manual wheelchair and more than 95% of the power chair users but less than 80% of the scooter users. We recommend using this approach in future ADA-ABA standards with a minimum width of 1095 mm (43 in.) which would accommodate more than 95% of all WhMD users in the sample. This would increase the width slightly but reduce the depth of the turning area significantly. When the entry and egress aisles are less than this width, the 360-degree turn clearances should be provided at the turning area. In effect, this condition is a space bounded by three sides and requires a lot more space because WhMD users cannot cut the corner like they can with a wider aisle width (Figure 4‒6).

Figure 4-6: Accommodation model depicting the minimum clear width required by users of manual wheelchairs, powered wheelchairs and scooters to complete a 180-degree turn around an obstacle.

Long Description: This data depicts the amount of space required by users of wheeled mobility devices to perform a 180-degree turn ("U-Turn") around an obstruction. The bold dashed line in the table and figure indicates the current ADA requirements, which vary based on the passage width and space available at the base of the turn. Findings from the Anthropometry of Wheeled Mobility Study indicate that a uniform width of at least 89.5 cm (35 in.) was required for 50% of the manual and power wheelchair users measured in this study to perform a 180-degree turn around the obstruction. A width of 109.5 cm (43 in.) was required in order to accommodate 95% of all users. These data are based on measurements of wheeled mobility users performing 180-degree turns around an obstruction, built with mock walls. An obstruction of 11 cm (4 in.) was fixed at a central location. Three moveable walls were constructed around the central fixed wall to form a U-shaped hallway of equal passage width. The enclosed space was incrementally and uniformly increased until a user could pass through the U-turn successfully. The minimum space required for completing a 180-degree turn around an obstruction within moving or knocking down any of the walls was recorded. Use of multiple short turns was allowed in contrast to a single continuous turn.

4.3.5.4 360-degree Turn

Accommodation models for 360-degree turns have been developed for the three types of devices based on the results (e.g. Figure 4‒7). There are substantial differences between the device types. Scooters require the largest turning spaces and manual chairs the least although there are some manual chair users that required spaces as large as many power chair users. The use of the 95th percentile in the power chair findings would increase the current requirements by 575 mm (23 in.). The size of the space required for the 95th percentile of scooter users would create even larger increases. Thus, due to the potential impact, these findings require some policy decisions on who to exclude, or a new way to address this design issue.

Dimensions for 360-degree turning spaces are used to determine the minimum spaces needed for turning around in spaces with only one point of entry. To better represent these situations, we based our measurements on a square-shaped space rather than circular as the former allows WhMD users to use the corners thereby optimizing space utilization. In spaces in which turning around is not critical for usability, another basis for determining the minimum floor area can be used as in the Fair Housing Accessibility Guidelines which only require a clear floor space outside the arc of a swinging door. This strategy is also already used for elevators and toilet stalls in the ADA-ABA Guidelines. A second strategy is to provide a turning space in all covered public spaces like toilet rooms, laundries and shared kitchenettes to accommodate the 50th or 75th percentile and, in addition, require at least one of each type of space somewhere in a building to be large enough to accommodate the largest devices. For example, one companion toilet room could be required in every building that accommodates both assisted use and the largest devices while the other toilet rooms meet less space intensive requirements. The largest turning space could also be required in places where the impact of increasing turning spaces is insignificant, for example, in a lobby or outdoors. Obviously, better space planning can also be used to avoid dead end spaces entirely but that cannot be mandated in a standard.

The implications of these findings are so significant that the authors recommend starting broad discussion of options among stakeholders before a concrete proposal is made to adopt a particular strategy.

Figure 4-7: Accommodation model depicting the minimum clear space required by users of manual wheelchairs, powered chairs and scooters to complete a 360-degree turn.

Long Description: This data depicts the amount of space required by users of wheeled mobility devices to perform a 360-degree turn. The bold dashed line in the table and figure indicates the current ADA requirement of a 152.5 cm (60 in.) turn space. Findings from the Anthropometry of Wheeled Mobility Study indicate that a square space of at least 160 x 160 cm (63 in.) was required for 50% of the manual wheelchair users measured in this study to perform a 360-degree turn. A space of 210 x 210 cm (83 in.) was required in order for 95% of manual wheelchair and power chair users to complete the turn, with 95% of scooter users needing a space of at least 250 x 250 cm (98 in.) These data are based on measurements of wheeled mobility users performing 360-degree turns within an enclosed square space built with mock walls. The enclosed space was incrementally varied from a size of 130 x 130 cm (51 in.) to 250 x 250 cm (98 in.) The minimum space required for completing 360-degree turn within moving or knocking down any of the walls was recorded. Use of multiple short turns was allowed in contrast to a single continuous turn.