Are you familiar with the term “poka-yoke?”
If so, then you know that a poka-yoke is a specially-designed feature of a process or a product that either prevents common mistakes or catches them before they cause trouble.
Often referred to as “mistake-proofing,” The term comes from the Japanese, meaning “inadvertent error” and “avoidance” and was popularized by the engineer Shingeo Shingo in his crusade to improve quality by eliminating human errors.
We see and use poka-yokes every day. For example, years ago, a dead car battery due to forgetfulness was a common problem. Since then, a poka-yoke was designed to sound a warning bell if the car lights are left on. A “warning” poka-yoke is a big help, but not fool proof. A more powerful poka-yoke has since been built-into newer cars and turns the lights on and off automatically.
Similarly, you see a wire gate swing out of the front of a school bus to guide children safely across the street; you are asked to double-enter a new password to guard against typos; wires are color-coded; highways have rumble strips.
All of these are features of a product or process that were specially designed to reduce the likelihood of a particular human error.
The best poka-yokes are easy to implement and involve inexpensive changes to the materials, tools, environment, or process. They fit the problem so perfectly they seem obvious once they are deployed. These poka-yokes render the specific human error that was targeted for elimination almost impossible to make.
For example, color-coding, redesigning forms, and other changes to the materials you use may reduce human errors. One company reduced accidents by replacing the white work gloves with neon gloves so that people were more aware of the hand position. One financial services company greatly reduced the number of transactions they had to reject due to customer error by analyzing the data, identifying which mistakes were easiest to make, and then redesigning the form to make required fields hard to overlook.
Yet a simple and powerful poka-yoke is almost never the first solution a team comes up with. The best ideas take creativity, collaboration, and the time to press on past the weaker solutions that come to mind first.
Most often, the first idea is one of the following:
(a) ask people to be more careful,
(b) ask management to send an email telling people to be more careful, or
(c) schedule a training session in which people are instructed to, yes, be more careful!
These solutions might help for a little while, but improvement is fleeting. Instead, we must keep brainstorming ideas until we can find a way to inexpensively make it much easier to do the work right or at least automatically alert a person when he or she has just made the mistake.
Here are some categories or types organized in increasing degrees of effective prevention:
- Job aides are a little less fleeting than exhorting people to be more careful, because these are present at the work site when the work is being done. Examples include: cheat sheets, check lists, laminated guides, photographic work instructions. We’ve all seen and used these. They make it easier to do things right because they aid our memory, if we consult them. Their weakness is that we can forget to consult them especially when we are rushed, tired, or distracted.
- Situational visual guides are better. When you design a form, design it to draw attention to the key items. If a particular type of transaction or operation requires an extra step that could easily be forgotten, consider using color coding or conditional formatting to highlight the important information. These can be effective and are often very quick and inexpensive to implement.
- Situational audio alerts can be even better such as alarm bells when you are about to make a mistake. If you were trying to reduce pick and pack errors, you might want to set up a bell that will ring whenever the package weight does not equal the expected weight for the order. This may be a little harder to implement, but in certain environments the audio signal may be much more effective than a visual cue.
- Automatic guides can reduce mistakes by leading you through the necessary fields or screens of a data transaction, the safest path through the warehouse, or the correct movement under a jigsaw. Automatic guides can often be designed fairly inexpensively, although may require some programming.
- Automatic controls are the most effective. These are design features that do not allow a certain mistake. For example, a gas cap may be tethered to the car to control against its loss. An automatic shutoff switch will prevent the work from continuing under the wrong conditions. A form requiring a valid entry is used to prevent missing or invalid entries. These generally involve more time and investment to implement, but if the mistakes have serious consequences automatic controls are the best option.
Fortunately there are some proven best-practices for “how to” design the best poka-yokes, and that will be the subject of our next post.