LNER AI ‘snake defect’ alert: data quality lessons for rail inspection engineers
Reviewed by Tom Sullivan

First reported on New Civil Engineer
30 Second Briefing
An artificial intelligence-powered inspection system on a London North Eastern Railway (LNER) service incorrectly flagged a snake lying across the line as a track defect, triggering an alert to LNER and Network Rail. The vision-based tool, mounted on in-service rolling stock to scan rails and trackbed for faults, treated the moving object as an infrastructure anomaly. The incident exposes the need for more robust training data and validation for AI defect-recognition models to distinguish transient obstructions from genuine rail geometry or component failures.
Technical Brief
- Incident confirms the need for explicit “transient object” classes (wildlife, debris) in training datasets.
- Rail operators will need documented false-positive/false-negative performance envelopes before integrating such systems into formal inspection regimes.
Our Take
Incidents where AI misclassifies benign objects as defects tend to be treated as nuisance events, but for operators like LNER they also provide rare, labelled edge‑case data that can materially improve model robustness if fed back into training pipelines.
For Network Rail, false positives from AI inspection tools are operationally preferable to missed defects, yet a high nuisance rate can quickly erode driver and maintainer trust, so tuning thresholds and designing clear human‑override workflows becomes as much a human‑factors issue as a software one.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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