HMI Design Best Practices Following ISA-101

High-Performance HMI Design

ANSI/ISA-101.01-2015 (ISA-101) provides a lifecycle-based framework for designing, implementing, operating, and maintaining Human Machine Interfaces (HMIs) for process automation. The standard focuses on improving operator situational awareness and reducing human error by prescribing a task-centered, ergonomic approach to display design, alarm presentation, navigation, and lifecycle governance. Implementing ISA-101 reduces risks during normal and abnormal process conditions and aligns HMI practice across engineering, operations, and supplier teams (ANSI/ISA-101.01-2015) (see References).

Purpose and Core Objectives

ISA-101's core objective is to "design, build, and maintain HMIs that result in more effective and efficient control of the process, in both normal and abnormal situations," enabling operators to detect, diagnose, and respond to abnormal situations in a timely and reliable manner. The standard applies across continuous, batch, and discrete manufacturing industries and addresses both graphical displays and the supporting hardware, software, and procedures that govern HMI use (ISA-101) [ISA].

Scope and Applicability

ISA-101 applies to any facility or process that uses an operator interface to a control system. Typical HMI functions covered by the standard include monitoring system status, controlling equipment, visualizing sensor and PLC data, responding to alarms, adjusting process parameters in real time, and tracking production performance. The lifecycle approach in ISA-101 spans initial requirements through design, testing, installation, training, operation, and ongoing maintenance and change control (ANSI/ISA-101.01-2015) [ARC].

Standards and Supporting Publications

ISA-101 is complemented by technical reports and guidance, notably ISA-TR101.02-2019 (HMI Usability and Performance), which expands on methods for HMI usability assessment, performance metrics, auditing, and validation. Organizations should adopt ISA-101 along with local human factors, safety, and industry-specific standards to ensure a complete HMI program (ISA-TR101.02-2019) [ISA-TR].

Display Hierarchy Architecture

ISA-101 prescribes a four-level display hierarchy based on task analysis and operator ergonomics, not Piping and Instrumentation Diagrams (P&IDs). The hierarchy helps operators maintain situational awareness while allowing drill-down to detail when necessary (ANSI/ISA-101.01-2015) [ANSI Blog].

Using this structure, designers must provide clear navigation so operators can move between levels without losing context. Consistent layout, naming, and escalation paths help preserve situational awareness during transitions between levels (ISA-101) [Yokogawa].

Design Phase Requirements

ISA-101 requires rigorous documentation and validation during the design phase. Key deliverables and activities include:

• User, task, and functional requirements — Define operator roles, tasks, frequency, timing constraints, and acceptable response times for abnormal situations. Task analysis drives the display hierarchy and navigation flows (ISA-101).
• HMI system design specification — Document hardware, software platforms, network architecture, security interfaces, and failure modes for operator workstations and consoles.
• Console and workstation design — Specify ergonomic requirements (screen size, resolution, viewing distance), input devices, lighting, and physical placement in control rooms to meet human factors criteria.
• Display design documentation — Produce prototype graphics for each display level, including color usage, iconography, and text standards to support consistent interpretation.
• Testing and validation plans — Define acceptance tests, operator training, and simulation scenarios to validate HMI performance before commissioning (ISA-101) [ISA].

Design Spec Checklist (typical)

• Documented realm of control for each operator station.
• Defined alarm priorities and response procedures.
• Navigation map linking Level 1–4 displays with unique identifiers.
• Standardized color and symbology guide.
• Performance targets for display refresh, trend update intervals, and alarm propagation.
• Change management and rollback procedures for display modifications.

Alarm and Procedure Philosophies

ISA-101 intersects with alarm management and operational procedures. It requires designers to present alarms in a way that supports timely, correct operator response, while avoiding information overload. Key expectations include:

• Alarm prioritization and presentation: Use clear prioritization (e.g., critical, high, medium, low) and present alarms consistently across displays. Alarm counts and time-since-first-active indicators support operator triage.
• Contextual alarm data: Provide immediate access to cause, consequence, and suggested operator action with each alarm. Linking alarms to relevant Level 3–4 diagnostic displays accelerates root-cause analysis.
• Procedural integration: Embed operational procedures (startups, shutdowns, grade changes) within the HMI where possible, and ensure procedural states are visible to all stakeholders. ISA-101 emphasizes that procedure presentation must be unambiguous, include safe limits, and record operator actions for accountability.

These concepts align with alarm-management best practices and reduce nuisance alarms that can desensitize operators. Effective HMI alarm design also coordinates with alarm management standards such as ISA-18.2 where applicable (ISA-101; ISA-TR101.02) [ISA-TR].

Batch and Discrete Process Considerations

ISA-101 provides guidance for batch operations and discrete manufacturing where sequence, recipe, and mode changes present unique HMI demands. For batch systems, the HMI must:

• Reflect current recipe and phase status, including step timers and derived KPIs.
• Support recipe selection with safeguards against incorrect recipe or parameter choices.
• Display batch records and traceability information inline with diagnostics to accelerate deviation investigations.

For discrete and hybrid systems, HMI design must expose mode states (manual/automatic), interlocks, and work-order information to ensure operators do not inadvertently violate process constraints (ISA-101) [Yokogawa].

Embedded Logic, Scripting, and Reproducibility

ISA-101 requires that any logic embedded in graphics or scripting be documented, versioned, and reproducible. Embedded scripts that define visibility, animation, or derived calculations must:

• Be traceable to requirements and approved during design reviews.
• Be stored in version control with change histories and rollback capabilities.
• Have clearly defined execution context and performance impacts documented (e.g., CPU and network loads, execution frequency).

This reduces operational risk from undocumented behavior and ensures that HMI changes follow the organization's change control process (ISA-101).

Data Visualization and Cognitive Load

ISA-101 emphasizes data visualization techniques that reduce cognitive load and accelerate recognition of abnormal conditions. Design recommendations include:

• Use of graphical aggregate indicators (e.g., sparklines, mini-trends) on Level 1 displays to reveal direction and rate-of-change without requiring drill-down.
• Prioritize numerical data that operators must act upon; de-emphasize non-actionable data.
• Apply consistent color semantics (e.g., green = normal, yellow = alert, red = alarm) and avoid using color alone—use shapes, icons, and text to convey status for color-blind accessibility.
• Display trend durations and sampling intervals for all historical views to avoid misinterpretation of transient events.

ISA-TR101.02 supplements this guidance with measurable usability and performance criteria, and recommends operator performance metrics such as time-to-detect, time-to-diagnose, and time-to-correct for scenario-based testing (ISA-TR101.02) [ISA-TR].

Lifecycle Management and Governance

One of ISA-101's distinguishing features is its lifecycle approach. The standard specifies activities and artifacts for each lifecycle phase: Requirements, Design, Implementation, Installation & Commissioning, Operation & Maintenance, and Decommissioning. Lifecycle governance reduces HMI-related rework and operational surprises by:

• Requiring documented requirements and acceptance criteria.
• Mandating design reviews with operations and maintainers present.
• Enforcing change control and regression testing for display updates.
• Including operator training and competency records as part of HMI commissioning.

These practices reduce both engineering and operational costs and preserve operational excellence across the asset lifecycle (ISA-101) [ARC].

Usability, Performance Measurement, and Validation

ISA-TR101.02-2019 provides practical methods for auditing HMI usability and performance. The report recommends:

• Defining objective operator performance measures (time-to-detect, time-to-diagnose, time-to-correct, error rates) and acceptance thresholds for new and modified displays.
• Using scenario-based testing with representative operators to validate that the HMI supports required tasks within the defined performance targets.
• Monitoring runtime metrics after commissioning, including frequency of navigation, alarm handling workload, and common operator actions to identify improvement opportunities.

Measurable performance targets help organizations prioritize HMI improvements and demonstrate ROI from HMI projects (ISA-TR101.02) [ISA-TR].

Implementation Checklist for Field Engineering Teams

Field-service engineers should follow a structured checklist derived from ISA-101 to ensure consistent, high-quality HMI deployments. The checklist includes:

• Confirm realm of control and user roles for each console (documented and approved).
• Verify display hierarchy is implemented and navigation links pass usability tests.
• Validate alarm presentation and that alarms include context, consequences, and suggested actions.
• Confirm all embedded logic is version-controlled, tested, and documented.
• Ensure console ergonomics meet viewing distances, resolution, and lighting requirements.
• Run scenario-based operator tests and record performance metrics against acceptance criteria.
• Implement change control for post-commissioning HMI modifications and maintain an HMI design library of approved UI components.

Patrion field engineers use this checklist during factory acceptance testing, site acceptance testing, and commissioning to reduce operational risks and speed handover to operations.

Specification Table: Sample HMI Technical Requirements