Revealing Hidden Usability Failures: 35% Error Reduction Through Human-in-the-Loop Evaluation

WEX Inc. | Fleet Fuel Management & Payments

Introduction

I built a human-in-the-loop (HITL) evaluation framework for WEX Inc. that revealed why traditional metrics were hiding real usability failures in their Account Manager workflows. The framework reduced operator errors by 35% and increased AI feature adoption from 34% to 61%.

Role: Senior UX Researcher | Timeline: 9 months

Problem Statement

WEX's eManager platform showed 85%+ task completion and low error rates in automated metrics, but Account Managers reported significant friction, workarounds, and wasted time. Automated logging was missing what mattered most: workflow efficiency and operator confidence in AI-assisted decisions.

Approach

  • Conducted audit of 12+ WEX products to identify gaps between metrics and user experience
  • Built human-in-the-loop evaluation framework combining automated data with qualitative observation
  • Conducted discovery interviews and task-based usability testing with Account Managers
  • Performed SQL analysis of behavioral data (override rates, alert fatigue patterns)
  • Triangulated findings: What users SAY + What users DO + What metrics SHOW

Solution

Developed and validated a human-in-the-loop evaluation methodology that:

  • Captured workflow inefficiencies that metrics couldn't see (workarounds, confidence erosion, time waste)
  • Prioritized improvements by severity × frequency based on user feedback and behavioral data
  • Provided business case for AI fraud detection investments with quantified impact
  • Established frameworks for ongoing evaluation of AI features across WEX's product portfolio

Impact

  • 35% reduction in Account Manager fraud approval errors
  • 34% → 61% increase in AI feature adoption (nearly doubled)
  • HITL evaluation framework adopted across WEX product portfolio
  • Reduced customer fraud losses through faster, more confident AI detection
  • Established research blueprint for validating AI features across the organization

Project Visuals

WEX HITL Case Study Slide 1 WEX HITL Case Study Slide 2

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