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Optimizing floor plans of accessible restrooms in elderly long-term care facilities: A path planning approach

May 2024
The Center For Health Design

Why does this study matter?
Our mobility often declines as we age, leading to a significant number of older adults who use wheelchairs or walkers for improved mobility. For those with diminished strength and control of abdominal or lower back muscles, using wheelchairs and walkers can make confined restroom spaces extremely difficult to navigate. Restroom design has to be optimized in order to avoid excessively disabling an entire population of mobility aid users as well as decrease excessive dependency on caregivers.

How was the study done?
This study used a virtual path-planning method for generating and evaluating how the floor plans of accessible restrooms affect mobility and convenience for older adults using wheelchairs and walkers. The parameterization rules for the “sample population” were gleaned from architectural design data sets and regulations from China, Japan, the UK, and the US (e.g., Barrier-Free in Buildings, ADA Standards; Accessible and Inclusive Design Guidance.; China Institute of Building Standard Design & Research) to inform minimum areas for accessible restrooms and the distances of fixtures from adjacencies and above finished floors. Floor plans were generated using parametric Rhino design software using the accessible dimension and clearance parameters, the inclusion of two or three fixtures, and motion models of autonomous and assisted mobility device users. Movement paths used vehicle path planning algorithms (e.g., Grasshopper plugin and Python) to simulate the most frequently observed sequence of actions for using both the sink and toilet within the restroom (e.g., entering the restroom → moving to the toilet → washing hands at the sink → leaving the restroom). To reduce redundant calculations and avoid symmetric floor plans with identical relative positions of fixtures, a sliding door was located on the right wall.           

What do we learn from the study?
Path lengths and turning angles were used as measures for the convenience of restroom use. The arithmetic means of the length score and turning angle score were used as a comprehensive index. A total of 8,475 floor plans without showers and 4,767 floor plans with showers were generated in Grasshopper. Based upon the combined use of the RS “fixed radius” curve and the Hybrid A* algorithm which selects the path with the shortest distance and the least turning angle to simulate the complex movements of wheelchair or walker users in restrooms, 92 optimal floor plans were identified in only one case did a floor plan include the sink and the toilet on the same wall. A paired t-test method was used to analyze the differences in optimal scores. The highest convenience score for a 2-fixture restroom layout resulted in the toilet at a 90-degree angle to the door and adjacent to the opposing wall; the sink’s optimal location was opposite the door. The most highly rated 3-fixture arrangement resulted in the toilet remaining on the same wall as in the 2-fixture arrangement but being relocated adjacent to the door to surrender its previous location to the shower; the sink remained opposite the door. Notably, a minimum room size for a 3-fixture layout required minimum dimensions of 2m x 2m (6.5’ x 6.5’). While not statistically significant. In all scores, the 45° side approach is the most effective for limiting both path length and turning angles, making corner fixtures more convenient for movement.

Can we say the results are definitive?
While this study offers many insights for leveraging algorithmic insights for the design of spaces to accommodate users with accessibility needs, the authors acknowledge that neither dominant hand-turning patterns nor those associated with various kinds of lifts were incorporated into the study. The biggest limitation, in my opinion, was the use of parameterization rules (limitations) gleaned from accessibility standards that are frequently inconsistent with the needs and capabilities of older adults, especially those using mobility and lift equipment and/or receiving single- or dual-side assistance.        

What’s the takeaway?
I think that this study offers fantastic insights into the ways in which design software might be leveraged by the design industry to benefit user groups with various capabilities and characteristics. In this way, we really can play to the strengths of the team on the field.


Summary of:
Yuan, H., & Shen, X. (2023). Optimizing floor plans of accessible restrooms in elderly long-term care facilities: A path planning approach. Architectural Engineering and Design Management, Pages in press.



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