The traffic light system is a visual inline quality method. Each operator gets a status - green, yellow or red - based on what the roving QC finds when checking their work.
How it works
- A roving inline checker visits every operator several times a day and checks a small sample (for example 7 pieces).
- Based on the result, the operator's status is set:
| Light | Typical rule | Action |
|---|---|---|
| Green | No defect in the sample | Normal checking |
| Yellow | One defect | Show the defect, check again sooner |
| Red | Two or more defects | Stop, correct method or machine, supervisor and IE involved |
- The light stays until a new check shows the problem is solved and it is set back to green.
- Every day starts clean, but the history is kept.
Why it works
- Fast feedback: problems are fixed at the source, within the hour.
- Visible: supervisors see at a glance where help is needed.
- Fair: the rule is the same for everyone and based on checks, not opinion.
- Data: the history shows which operations and operators need training or method changes.
Tips for success
- Train checkers to use the same sample size and rules on every line.
- Treat red as a call for help, not a punishment - look at the machine, the method and the materials first.
- Review the week's red and yellow history with IE to plan training and method improvements.
Tip: Show the lights on the production follow-up screen next to hourly output. A line can be on target and still need attention if one operation is red.