Definition
An andon is a visual signaling system used on the production floor to communicate the real-time status of operations and to immediately highlight abnormalities. In its most recognized form, it is an overhead display board with rows of lights or numbers corresponding to workstations. When a worker encounters a problem — a quality defect, a parts shortage, an equipment issue, or a delay — they activate the andon (by pulling a cord or pressing a button), which lights up the board and signals a team leader to respond.
The purpose of andon is not to stop production. It is to make problems visible so they can be addressed at the source, before they propagate downstream.
Japanese Origin
The word andon (行灯, also written 行燈) originally referred to a paper-enclosed lamp popular during the Edo period (1603-1867). The character 行 means “to go” and 灯 means “lamp” — literally a portable lantern, made of washi paper stretched over a frame of bamboo or wood, protecting an oil flame from wind.
As Japan electrified in the Meiji era, the traditional andon faded from daily life. But the word was repurposed within Toyota’s production system: just as the original andon made things visible in a dark room, the manufacturing andon makes problems visible on the production floor. It is a light that draws attention to where something needs attention.
History at Toyota
The roots of andon trace back to Sakichi Toyoda’s 1896 invention of a power loom with an automatic weft-breakage stopping device — the origin of jidoka. When a thread broke, the loom stopped itself. But someone still needed to know it had stopped. The andon concept emerged from this need: once machines can detect their own abnormalities, there must be a system to make those abnormalities visible.
1955 — Toyota adopted stop-button-linked andons on the Crown assembly line at the Honsha Plant, allowing operators to identify which process had caused a line stoppage. This was one of the earliest documented applications of andon in Toyota’s automobile assembly.
1966 — Andon was installed at the Kamigo Plant engine assembly line. Toyota’s 75-year corporate history describes this as the moment that completed “line automation with a human touch” — jidoka in its full form. The official history specifically calls out that andon boards and lights were installed “in positions that are highly visible to supervisors,” and when a problem occurs, “andon are lit up — either manually or automatically — so a supervisor can immediately come to the source of the problem and address it.”
Taiichi Ohno was the primary driver. He developed TPS through repeated trial and error at the Honsha Machinery Plant from the late 1940s through the 1960s, with executive backing from Eiji Toyoda. Andon was not a single invention but an evolutionary development within the broader jidoka pillar of TPS.
2014 onward — Toyota began replacing the traditional overhead andon cord with waist-high buttons in some plants, removing overhead clutter and improving ergonomics. The mechanism changed, but the purpose did not.
How It Actually Works
This is where most descriptions of andon go wrong. The common Western understanding — “worker pulls cord, line stops” — is a serious oversimplification.
What actually happens at Toyota:
- A worker encounters a problem (quality issue, delay, something abnormal)
- The worker pulls the cord or presses the button — this does not immediately stop the line
- A light illuminates on the overhead andon board showing which station has an issue, and music plays
- A team leader arrives within seconds — Toyota maintains roughly one team leader for every eight workers
- The team leader helps resolve the issue
- If resolved before cycle time expires, the line never stops
- If not resolved in time, the line stops at a fixed position (the boundary of the workstation), not wherever the product happens to be
The fixed-position stop is critical. It ensures that a pause at one workstation does not cascade to others. The line stops cleanly, and restarts cleanly.
The cord is pulled constantly. At Toyota’s Georgetown, Kentucky plant, workers activate the andon approximately 2,000 times per week. This is considered healthy — it means the system is working and problems are being surfaced. By contrast, reports from a Ford truck plant showed the cord being pulled approximately twice per week. The difference is not fewer problems at Ford; it is a culture where problems are hidden rather than addressed.
Implementation Guidance
Andon is simple in concept but demanding in execution. The hardware is the easy part — what makes it work is the management system around it.
Prerequisites:
- Team leaders must be in position to respond within seconds. Without a sufficient ratio of team leaders to workers (Toyota uses roughly 1:8), the andon becomes a signal nobody answers.
- Standardized work must be established. Workers can only recognize abnormalities if there is a clear standard for what “normal” looks like.
- A problem-solving culture must exist. When the line stops, the response must be root cause investigation and permanent countermeasures — not blame and not just a quick fix to restart.
Start here:
- Begin with a simple signal — even a hand-raise or a flag — before investing in electronic boards
- Train team leaders to respond immediately and thank the worker for surfacing the problem
- Track andon activations as a positive metric: more activations early on means the system is working
- Connect andon stops to a structured problem-solving process (A3, 5-Why, etc.)
Common Mistakes
Installing the hardware without the management system. This is the single most common failure. Companies buy andon boards and cords, but have no team leaders positioned to respond. The lights go on, nobody comes, and workers stop pulling the cord.
Treating line stops as failures. If management reacts to andon activations with frustration or punishment, workers will stop using the system. At Toyota, there is no punishment for pulling the cord — leaders would rather respond to a false alarm than miss a real problem.
Confusing andon with a production status display. A screen showing “Line 3: Running” is a scoreboard, not an andon. The defining feature of andon is that it is activated by the person doing the work to call for help. It is a pull system for problem-solving.
Skipping the fixed-position stop. Many Western implementations stop the line wherever the product happens to be when the cord is pulled. This creates chaos. Toyota’s fixed-position stop system — where the line stops at the boundary between workstations — minimizes disruption while preserving jidoka.
Not asking why. An andon activation that results in “just restart” is waste. Every stop is an opportunity to understand the root cause and prevent recurrence. Without this discipline, andon becomes noise.