Question

A seat is to be designed for a public bus for adult Indian population. While designing, which option needs to be considered so that MOST of the relevant category population can sit on it comfortably?

• A. Seat height is 95th percentile of sitting height and seat breadth is 5th percentile of hip breadth of adult population.
• B. Seat height is 50th percentile of sitting height and seat breadth is 95th percentile of hip breadth of adult population.
• C. Seat height is 5th percentile of sitting height and seat breadth is 5th percentile of hip breadth of adult population.
• D. Seat height is 50th percentile of sitting height and seat breadth is 5th percentile of hip breadth of adult population.

Hint:

Remember the golden rule of ergonomics: "Design clearances (like seat widths or door heights) for the maximum (95th percentile), and design reaches (like button placement or seat heights) for the minimum (5th or 50th percentile)."

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
This question belongs to the topic of

Ergonomics and Anthropometric Design.
We are asked to choose the optimal percentile values for seat height and seat breadth for a public bus to ensure that the maximum percentage of the adult Indian population can sit comfortably.

Step 2: Key Formula or Approach:
In ergonomic design, the choice of percentile depends on the physical constraint we are addressing:

• Seat Height: If a seat is too high, shorter people cannot rest their feet flat on the floor, causing discomfort. If a seat is too low, taller people can still use it, though with more knee flexion. To accommodate the largest range of heights, we design for a lower percentile or the mean (50th percentile) to balance usability.

• Seat Breadth (Width): If a seat is too narrow, larger individuals cannot fit. Sparing extra width does not prevent thin individuals from sitting. Therefore, we design seat breadth for a high percentile (95th percentile) to accommodate larger bodies.


Step 3: Detailed Explanation:

• Let us analyze the options:
- Seat height: Designing height for the 95th percentile would make the seat extremely high, meaning 95% of the population would have their legs dangling uncomfortably. A 50th percentile design targets the average body size, providing a reasonable height for most users.
- Seat breadth: If we choose the 5th percentile for breadth, the seat will be very narrow, and 95% of the population will find it too cramped or won't fit at all. Designing the breadth for the 95th percentile ensures that 95% of the population can sit without feeling squeezed.
- Therefore, the ideal configuration is to balance the seat height at the 50th percentile and maximize the seat breadth at the 95th percentile. This corresponds to Option (B).


Step 4: Final Answer:
Option (B) is the correct ergonomic design strategy.