The Role of HMI Design in Reducing Operator Error

Human-Machine Interface design is often treated as a cosmetic afterthought in automation projects — whatever layout the PLC programmer finds convenient. In practice, HMI design has a measurable effect on operator error rates, especially during abnormal or high-stress situations.

Common HMI design mistakes

• Overuse of bright colors for normal status, leaving nothing visually distinct for actual alarms
• Screens dense with data that bury the one value an operator actually needs during an abnormal event
• Inconsistent navigation and terminology between screens designed by different engineers over time
• Critical controls placed close to frequently-used, low-consequence buttons, inviting accidental activation

Principles that actually reduce error

High-performance HMI design (following principles from ISA-101 and related human-factors research) favors muted, low-saturation color palettes for normal operation, reserving bright alarm colors exclusively for genuine abnormal conditions — so an operator's eye is drawn to what matters without being desensitized by constant visual noise.

Why this matters more as systems get more connected

As MES and IIoT data get surfaced on operator screens alongside traditional control data, the risk of overwhelming the interface grows. Deliberate information hierarchy — what's always visible, what's one click away, what's only shown during an alarm — becomes more important, not less, as the amount of available data increases.