It can be obvious if it’s designed right!

Andrea Díaz Navarro
2 min readJan 12, 2021

Have you ever wondered why does USBs can only enter facing one side? Or why does the alarm won’t stop until the car passengers have fastened their seatbelts? The answer is: Poka-Yoke .

“Poka Yoke is a lean manufacturing tool that refers to ‘mistake-proofing’ or ‘error-proofing’ a process.”

It was originally created by Shigeo Shingo in the 1960s and implemented at Toyota as part of the Toyota Production System (TPS). [1] Its main objective is to prevent incorrect parts from being made or assembled, and can easily identify any flaw or error involved in the process.

However, the term is not exclusive for the manufacturing industry. Poka-yokes are closer than you think to our daily life. Here are a few examples I’m sure you can relate to:

  1. Washing machines: It won’t start unless the door is properly closed and can’t be opened until the cycle has finished.
  2. Child resistant caps: To make it difficult for children to consume a specific content.
  3. Cutters (Cutting tool): With a retractable blade that only pops out when the handle is pressed down.

Yet, there are some poka-yokes which are useless or simply applied incorrectly. For example, a ‘push’ sign is contradictory and confusing if a handle is part of a door’s design. Have you ever experienced a confident ‘push’ when it was an actual ‘pull’?

Norman door (n.):
1. A door where the design tells you to do the opposite of what you’re actually supposed to do.
2. A door that gives you the wrong signal and needs a sign to correct it.

Figure 2. Norman Door Example

“Why do you have to have a sign that says push or pull?… why not make it obvious?!“— Donald Norman

I considered this video one of my favorites to understand the user’s behavior in order to come up with creative and simple solutions. As the design guru explains, there are some basic design principles for a human-centered design: discoverability and feedback. These elements form the basis of how engineers and designers work today.

Figure 1. Video: It’s not you. Bad doors are everywhere.

The human-centered door is the one that as you walk up through, you are not even aware of it. He explains that with a flat plate, there is only opportunity for a ‘push’ and consequently, a result of a ‘mistake-proofing’ design.

Even though it might seem obvious, engineers and designers should apply the concepts in order to enhance the experience of whoever is interacting with the product or process. It’s definitely valuable to understand the natural behavior to make an obvious interaction… simply with our design!